text:
Proteomics/Protein - Protein Interactions/Jena Links

Page Edited and Updated by: Dan Surdyk E-mail: dfs6389@rit.edu

This Section:

Links from the Jena Center for Bioinformatics Page
Please note that the following page of references was quoted from the following online source:

Experimental Data

 * AllFuse (European Bioinformatics Institute)
 * functional association of proteins in complete genomes
 * http://cgg.ebi.ac.uk/services/allfuse/

 * ASEdb (Harvard University)
 * Alanine Scanning Energetics DataBase
 * database of hotspots in 3D protein structures
 * http://thornlab.cgr.harvard.edu/hotspot/index.php

 * Bacteriome.org (University of Toronto)
 * bacterial protein interaction database
 * database integrating physical (protein-protein) and functional interactions within the context of an E. coli knowledgebase
 * http://www.bacteriome.org/

 * BID (A & M University Texas)
 * Binding Interface Database
 * http://tsailab.org/BID/index.php

 * BioGRID (Samuel Lunenfeld Research Institute)
 * The General Repository for Interaction Datasets
 * database of genetic and physical interactions
 * http://www.thebiogrid.org/

 * BOND (Thomson Corp.)
 * Biomolecular Object Network Databank
 * new resource to perform cross-database searches of available sequence, interaction, complex and pathway information
 * integrates a range of component databases including Genbank and BIND, the Biomolecular Interaction Network Database
 * http://bond.unleashedinformatics.com/Action?

 * (UCLA)
 * Database of Interacting Proteins
 * http://dip.doe-mbi.ucla.edu/DIP

 * Drosophila Protein Interaction Map (PIM) Database (Wayne State University)
 * http://proteome.wayne.edu/PIMdb.html

 * EchoBASE (University of York)
 * integrated post-genomic database for E. coli
 * http://www.ecoli-york.org/

 * Genomic Knowledge Database (RIKEN, Institute of Physical and Chemical Research)
 * integrates various types of biological and biomedical databases in order to discover disease-related cascades and medicinal target candidates
 * http://fuminobmt.gsc.riken.jp/big/Research/Genomic%20Knowledge%20Base%20Research%20Team/

 * HIV-1 - Human Protein Interaction Database (NCBI)
 * http://www.ncbi.nlm.nih.gov/RefSeq/HIVInteractions/index.html
 * summary of all known interactions of HIV-1 proteins with host cell proteins, other HIV-1 proteins, or proteins from disease organisms associated with HIV / AIDS

 * hp-DPI (National Health Research Institutes)
 * Helicobacter Pylori Database of Protein Interactomes
 * combined with experimental and inferring interactions
 * http://dpi.nhri.org.tw/protein/hp/ORF/index.php

 * HPID (Inha University)
 * Human Protein Intercation Database
 * http://wilab.inha.ac.kr/hpid/

 * HUGE ppi (Kazusa DNA Research Institute)
 * database of protein-protein interactions between large KIAAproteins
 * http://www.kazusa.or.jp/huge/ppi/

 * HUGE: Human Unidentified Gene-Encoded large proteins
 * http://www.kazusa.or.jp/huge/

 * Human Protein Reference Database (Johns Hopkins University & The Institute of Bioinformatics, India)
 * platform to visually depict and integrate information pertaining to domain architecture, post-translational modifications, interaction networks and disease association for each protein in the human proteome
 * http://www.hprd.org/

 * ICBS (University of California)
 * Inter-Chain Beta-Sheets database
 * http://contact14.ics.uci.edu/index.html

 * KDBI (National University of Singapore)
 * database of Kinetic Data of Bio-molecular Interactions
 * http://xin.cz3.nus.edu.sg/group/kdbi/kdbi.asp

 * KEGG BRITE (Kyoto University)
 * Biomolecular Relations in Information Transmission and Expression
 * functional hierarchies and binary relationships of biological entities
 * http://www.genome.ad.jp/brite/brite.html

 * MINT (CBM, Rome)
 * Molecular INTeractions database
 * database of functional interactions between biological molecules: RNA, DNA, proteins
 * http://cbm.bio.uniroma2.it/mint/

 * DOMINO - DOMain peptide INteractiOns database,
 * describing interactions mediated by protein-interaction domains
 * http://mint.bio.uniroma2.it/domino/search/searchWelcome.do

 * molmovdb.org (Yale University)
 * database of macromolecular movements with associated tools for flexibility and geometric analysis
 * http://molmovdb.mbb.yale.edu/

 * MPact (MIPS)
 * yeast protein-protein interaction data contained in
 * http://mips.gsf.de/genre/proj/mpact/index.html
 * Comprehensive Yeast Genome Database
 * http://mips.gsf.de/genre/proj/yeast/index.jspCYGD

 * MPPI (MIPS)
 * Mammalian Protein-Protein Interaction database
 * http://mips.gsf.de/proj/ppi/

 * PDZBase (Weill Medical College of Cornell University)
 * manually curated protein-protein interaction database developed specifically for interactions involving PDZ domains
 * http://icb.med.cornell.edu/services/pdz/start

 * PepCyber: P~PEP (University of Minnesota)
 * database of human protein-protein interactions mediated by phosphoprotein binding domains (PPBDs)
 * http://pepcyber.umn.edu/PPEP/

 * POINT (National Health Research Institutes & National Taiwan University)
 * functional database for the prediction of the human protein-protein interactome based on available orthologous interactome datasets
 * integrates several publicly accessible databases, with emphasis placed on the extraction of a large quantity of mouse, fruit fly, worm and yeast protein-protein interactions datasets from the Database of Interacting Proteins (DIP), followed by conversion of them into a predicted human interactome
 * http://phos.bioinformatics.tw/

 * PRIME (Human Genome Center, University of Tokyo)
 * PRotein Interactions and Molecular Information databasE
 * integrated gene/protein informatics database based on natural language processing
 * http://prime.ontology.ims.u-tokyo.ac.jp:8081/

 * ProtoArray&reg (Invitrogen)
 * http://www.invitrogen.com/content.cfm?pageid=10400

 * Protein Interaction Database (Protein Lounge)
 * database lists thousands of human protein-protein interactions
 * created through in-dept research of hundreds of signal transduction pathways
 * http://www.proteinlounge.com/inter_home.asp

 * Protein Interaction Maps - PIMs (Hybrigenics)
 * functional proteomics software platform, dedicated to the exploration of protein pathways
 * PIM's available for Helicobacter pylori, Hepatitis C Virus, Drosophila and TGF-Beta
 * http://pim.hybrigenics.com/pimrider/pimriderlobby/PimRiderLobby.jsp

 * Protein-Protein Interaction Panel using mouse full-length cDNAs (RIKEN, Yokohama Institute)
 * see Suzuki et al., Genome Res. 2001, 11, 1758-1765. [PubMed]
 * http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=11591653&query_hl=5&itool=pubmed_docsum
 * http://genome.gsc.riken.go.jp/ppi/

 * Protein-Protein Interaction Viewer [+ FANTOM2 Viewer] (RIKEN Yokohama Institute)
 * http://fantom21.gsc.riken.go.jp/PPI/

 * PSIbase (BioSystems Dept., KAIST & BiO centre)
 * structural interactome map of all proteins
 * http://psibase.kobic.re.kr/

 * Repair-FunMap (Temple University)
 * database that provides the functional networking of proteins related to DNA repair processes in the cell
 * capable of generating functional maps of interacting proteins around a protein of interest
 * http://guanyin.chem.temple.edu:8080/FunMap/index.html

 * SNAPPIView (University of Dundee)
 * Structures, iNterfaces and Alignments for Protein-Protein Interactions
 * object-oriented database of domain-domain interactions observed in structural data
 * http://www.compbio.dundee.ac.uk/SNAPPI/downloads.jsp

 * SPIN-PP Server (Columbia University)
 * Surface Properties of INterfaces - Protein Protein interfaces
 * database of all protein-protein interactions in the PDB
 * http://trantor.bioc.columbia.edu/cgi-bin/SPIN/

 * Yeast Interacting Proteins Database (Kanazawa University)
 * yeast protein interactome view data with a Genetic Network Visualization System
 * http://itolab.cb.k.u-tokyo.ac.jp/Y2H/
 * http://itolab.cb.k.u-tokyo.ac.jp/webgen/webgen.html

 * Yeast Protein Linkage Map Data (University of Washington)
 * http://depts.washington.edu/sfields/yp_interactions/index.html

 * YPD&#8482 (BIOBASE)
 * Yeast Proteome Database
 * comprehensive knowledge resource for the proteins of S. cerevisiae
 * http://www.biobase-international.com/pages/index.php?id=ypd

Predictions

 * ADAN (EMBL)
 * prediction of protein-protein interAction of moDular domAiNs
 * http://adan-embl.ibmc.umh.es

 * AtPID (Northeast Forest University)
 * Arabidopsis Thaliana Protein Interactome Database
 * rich source of information for system-level understanding of gene function and biological processes in A. thaliana
 * integrates data from several bioinformatics prediction methods and manually collected information from the literature
 * contains data relevant to protein-protein interaction, protein subcellular location, ortholog maps, domain attributes and gene regulation
 * http://atpid.biosino.org/

 * E. Coli Predicted Protein Interactions Database (Universidad Aut&oacutenoma Cantoblanco)
 * in silico two-hybrid system for the prediction of interaction partners to the entire E. coli genome
 * http://www.pdg.cnb.uam.es/i2h/

 * Fly-DPI ( National Health Research Institutes)
 * statistical model to predict protein interaction networks of Drosophila melanogaster
 * http://flydpi.nhri.org.tw/protein/fly/general_search/

 * Genes2Networks (Mount Sinai School of Medicine)
 * connecting lists of gene symbols using mammalian protein interactions databases
 * powerful web-based software that can help to interpret lists of genes and proteins
 * can be used to find relationships between genes and proteins from seed lists, and predict additional genes or proteins that may play key roles in common pathways or protein complexes
 * http://actin.pharm.mssm.edu/genes2networks/

 * HAPPI (Indiana University School of Informatics, Purdue University School of Science)
 * Human Annotated and Predicted Protein Interaction database
 * collected or inferred computationally from public sources
 * http://bio.informatics.iupui.edu/HAPPI/

 * HPID (Inha University)
 * Human Protein Interaction Database
 * http://wilab.inha.ac.kr/hpid/

 * ICBS (University of California)
 * Inter-Chain Beta-Sheets
 * database of protein-protein interactions mediated by interchain ß-sheet formation
 * http://contact14.ics.uci.edu/index.html

 * INTERPARE (National Genome Information Center, Korea Research Institute of Bioscience and Biotechnology &amp BiO Centre)
 * protein "interfaceome" database
 * contains large-scale interface data of proteins with known 3D-structures
 * http://interpare.net/

 * NOXclass (Max-Planck-Institut f&uumlr Informatik)
 * SVM (support vector machine algorithm) classifier identifying protein-protein interaction types
 * http://noxclass.bioinf.mpi-inf.mpg.de/

 * OPHID (Ontario Cancer Institute & University of Toronto)
 * Online Predicted Human Interaction Database
 * designed to be both a resource for the laboratory scientist to explore known and predicted protein-protein interactions, and to facilitate bioinformatics initiatives exploring protein interaction networks
 * http://ophid.utoronto.ca/

 * PIBASE (University of California)
 * comprehensive database of structurally defined interfaces between pairs of protein domains
 * http://alto.compbio.ucsf.edu/pibase/

 * PPIDB (Iowa State University)
 * database of protein-protein interfaces derived from all protein-protein complexes available in the Protein Data Bank
 * http://ppidb.cs.iastate.edu/index.htm

 * Predictome (Boston University)
 * database of putative links between proteins using sequence data of genomes of 44 microorganisms
 * http://predictome.bu.edu/static/sources.html

 * PreSPI (Information and Communications University)
 * PREdiction System for Protein Interaction
 * domain combination based protein interaction prediction system
 * http://prespi.icu.ac.kr/

 * PRIMOS (BIOMIS, FH Hagenberg)
 * PRotein Interaction and MOlecule Search) database
 * integrated knowledge portal for analysing integrated protein-protein interaction data
 * http://biomis.fh-hagenberg.at/isp/Primos/

 * PRISM (Koc University)
 * PRotein Interactions by Structural Matching
 * explore protein interfaces and predict protein-protein interactions
 * http://gordion.hpc.eng.ku.edu.tr/prism/

 * PRODISTIN Web Site (LGPD/IBDM, CNRS)
 * web service to functionally classify genes/proteins from any type of interaction network
 * http://crfb.univ-mrs.fr/webdistin/

 * Prolinks Database (University of California)
 * collection of inference methods used to predict functional linkages between proteins
 * methods include the Phylogenetic Profile method, which uses the presence and absence of proteins across multiple genomes to detect functional linkages the Gene Cluster method, which uses genome proximity to predict functional linkage Rosetta Stone, which uses a gene fusion event in a second organism to infer functional relatedness and the Gene Neighbor method, which uses both gene proximity and phylogenetic distribution to infer linkage
 * http://www.doe-mbi.ucla.edu/Services/MTBreg/prolinks.html

 * SNAPPI-Predict (University of Dundee)
 * Structures, iNterfaces and Alignments for Protein-Protein Interactions
 * protein-protein interaction prediction program
 * http://www.compbio.dundee.ac.uk/SNAPPI/predict.jsp

 * SPIDer (Beijing Normal University)
 * database of predicted protein-protein interaction network in yeast
 * effective method of reconstructing a yeast protein interaction network by measuring relative specificity similarity (RSS) between two Gene Ontology (GO) terms
 * http://cmb.bnu.edu.cn/SPIDer/index.html

Related Domain, Pathway and Network Databases

 * BioCarta (BioCarta)
 * charting pathways of life
 * http://www.biocarta.com/genes/index.asp

 * BioCyc (SRI)
 * includes the literature-derived pathway/genome databases Ecocyc (encyclopedia of E. coli genes and metabolism) & MetaCyc (metabolic pathways and enzymes from 150 species) as well as computationally derived genome/pathway databases for 12 species
 * http://biocyc.org

 * CSNDB (NIHS)
 * Cell Signaling Networks DataBase
 * http://www.chem.ac.ru/Chemistry/Databases/CSNDB.en.html

 * DAPID (National Chiao Tung University)
 * Domain Annotated Protein-protein Interaction Database
 * database of domain-annotated protein interactions inferred from three-dimensional (3D) interacting domains of protein complexes in the Protein Data Bank (PDB)
 * http://gemdock.life.nctu.edu.tw/dapid

 * DIMA (MIPS, TUM)
 * Domain Interaction MAp
 * comprehensive resource for functional and physical interactions among conserved protein-domains
 * http://mips.gsf.de/genre/proj/dima2/

 * DOMINE (University of Texas at Dallas)
 * database of known and predicted protein domain (domain-domain) interactions
 * http://domine.utdallas.edu/cgi-bin/Domine

 * DOQCS (NCBS)
 * Database Of Quantitative Cellular Signaling
 * http://doqcs.ncbs.res.in./

 * EDGEdb (University of Massachusetts Medical School)
 * C. Elegans Differential Gene Expression database
 * http://edgedb.umassmed.edu/IndexAction.dojsessionid=83C4B5E969161C36F9CFA68A8C0EAF3D

 * EMP (EMP Project Inc.)
 * Enzymes and Metabolic Pathways
 * http://www.empproject.com/about/

 * HotSprint (KOC University, Turkey)
 * database of computational hot spots in protein interfaces
 * http://prism.ccbb.ku.edu.tr/hotsprint/index.php

 * iHOP (Computational Biology Center, Memorial Sloan-Kettering Cancer Center, USA & Protein Design Group, National Center of Biotechnology, Spain)
 * Information Hyperlinked Over Proteins
 * gene network for navigating the literature
 * http://www.ihop-net.org/UniPub/iHOP/

 * InCeP (Kazusa DNA Research Institute)
 * database for IntraCellular Pathway based on mKIAA protein-protein interactions
 * http://www.kazusa.or.jp/create/index.jsp

 * InterDom (Laboratories for Information Technology)
 * database of putative INTERacting protein DOMains derived from multiple sources
 * http://interdom.lit.org.sg/

 * KEGG
 * Kyoto Encyclopedia of Genes and Genomes [*::http://www.genome.ad.jp/kegg/metabolism.htmlMetabolic Pathways | *::http://www.genome.ad.jp/kegg/regulation.htmlRegulatory Pathways]
 * http://www.genome.ad.jp/kegg/

 * KEGG LIGAND
 * database of chemical compounds and reactions in biological pathways
 * http://www.genome.ad.jp/dbget/ligand.html

 * Kinase Pathway Database (Human Genome Center)
 * integrated database concerning completed sequenced major eukaryotes, which contains the classification of protein kinases and their functional conservation and orthologous tables among species, protein-protein interaction data, domain information, structural information, and automatic pathway graph image interface
 * http://kinasedb.ontology.ims.u-tokyo.ac.jp/

 * Pathway Database (Protein Lounge)
 * database of protein signaling and metabolic pathways
 * http://www.proteinlounge.com/pathway_home.asp

 * Pfam (Sanger Institute)
 * Protein FAMilies database of alignments and HMM
 * http://www.sanger.ac.uk/Software/Pfam/

 * PUMA2 (Argonne National Lab)
 * evolutionary analysis of metabolism
 * http://compbio.mcs.anl.gov/puma2/

 * Roche Applied Science 'Biochemical Pathways'
 * http://www.expasy.org/cgi-bin/search-biochem-index

 * SCOPPI (TU Dresden)
 * Structural Classification Of Protein-Protein Interfaces
 * http://www.scoppi.org/

 * SMART (EMBL Heidelberg)
 * Simple Modular Architecture Research Tool
 * http://smart.embl-heidelberg.de

 * SPAD (Kyushu University)
 * Signaling PAthway Database
 * http://www.grt.kyushu-u.ac.jp/spad/

 * SoyBase (Yale University)
 * soybean metabolism
 * http://cgsc.biology.yale.edu/metab.html

 * TRANSCompel (BIOBASE)
 * database of composite regulatory elements affecting gene transciption in eukaryotes [*::http://www.biobase.de/pages/guided_tours/transcompel/tour.htmlGuided Tour]
 * http://www.gene-regulation.com/pub/databases.html#transcompel

 * TRANSPATH (BIOBASE)
 * database on molecular pathways and cellular network modelling [*::http://www.biobase.de/pages/guided_tours/transpath/tour.htmlGuided Tour]
 * http://www.biobase-international.com/pages/index.php?id=transpathdatabases

 * UniHI (Charite - Medical Devision, Humboldt-University zu Berlin)
 * Unified Human Interactome
 * comprehensive database of the computational and experimental based human protein interaction networks
 * http://theoderich.fb3.mdc-berlin.de:8080/unihi/home

 * The Interactive Fly (Society for Developmental Biology)
 * a guide to Drosophila genes and their role in development
 * includes information on *::http://www.sdbonline.org/fly/aimain/5zygotic.htmbiochemical pathways
 * http://www.sdbonline.org/fly/aimain/1aahome.htm

 * Wnt Signaling Pathway (Stanford University Medical Center)
 * http://www.stanford.edu/%7Ernusse/wntwindow.html

 * Yeast Interactome (Boston University)
 * http://structure.bu.edu/rakesh/myindex.html
 * interaction map with valuable information regarding to biochemical processes

 * Yeast Pathways in the Comprehensive Yeast Genome Database (MIPS)
 * http://mips.gsf.de/proj/yeast/CYGD/db/pathway_index.html

Webtools

 * APID (Cancer Research Center)
 * Agile Protein Interaction DataAnalyzer
 * interactive web-tool
 * all known experimentally validated protein-protein interactions
 * http://bioinfow.dep.usal.es/apid/index.htm

 * ADVICE (Institute for Infocomm Research)
 * Automated Detection and Validation of Interaction by Co-Evolution
 * prediction and validation of protein-protein interactions
 * http://advice.i2r.a-star.edu.sg/

 * BioLayout Java (EMBL)
 * automatic graph layout algorithm for similarity and network visualization
 * http://cgg.ebi.ac.uk/services/biolayout/

 * eFsite (Osaka University)
 * Electrostatic surface of Functional-SITE
 * database for molecular surfaces of proteins' functional sites, displaying the electrostatic potentials and hydrophobic properties together on the Connolly surfaces of the active sites
 * http://ef-site.hgc.jp/eF-site/

 * Expression Profiler (European Bioinformatics Institute)
 * explores protein interaction data using expression data
 * http://ep.ebi.ac.uk/EP/PPI/

 * FunSimMat (Max Planck Institute for Informatics)
 * Functional Similarity Matrix
 * comprehensive functional similarity database
 * http://funsimmat.bioinf.mpi-inf.mpg.de/

 * IntAct Project (European Bioinformatics Institute)
 * database and toolkit for the storage, presentation and analysis of protein interactions
 * http://www.ebi.ac.uk/intact/index.html

 * InterPreTS (EMBL)
 * protein INTERaction PREdiction through Tertiary Structure
 * http://speedy.embl-heidelberg.de/people/patrick/interprets/index.html

 * InterProSurf (University of Texas Medical Branch)
 * web server for predicting the functional sites nonprotein surfaces
 * http://curie.utmb.edu/

 * InterViewer (Inha University)
 * visualization oflarge-scale protein interaction networks
 * http://interviewer.inha.ac.kr/

 * InterWeaver (Institute for InfoComm Research)
 * web server of interaction reports
 * http://interweaver.i2r.a-star.edu.sg/

 * iPPI (National Bioinformatics Center Cuba)
 * infers protein-protein interactions through homology search
 * http://www.bioinfo.cu/iPPI.html

 * IPPRED (Centre de Bioinformatique de Bordeaux)
 * proteins interactions inference server
 * infers interactions through homology search
 * http://cbi.labri.fr/outils/ippred/IS_part_simple.php

 * iSPOT (Universita di Roma)
 * prediction of protein-protein interactions mediated by families of peptide recognition modules
 * http://cbm.bio.uniroma2.it/ispot/

 * Medusa (EMBL)
 * interface to the *::http://string.embl.de/STRING protein interaction database
 * a general graph visualization tool
 * http://www.bork.embl-heidelberg.de/medusa/

 * NetAlign (Lab of Protein Crystallography, USTC)
 * a web-based tool for comparison of protein interaction networks
 * http://www1.ustc.edu.cn/lab/pcrystal/NetAlign/

 * PathBLAST (Whitehead Institute)
 * network alignment and search tool for comparing protein interaction networks across species to identify protein pathways and complexes that have been conserved by evolution
 * http://www.pathblast.org/

 * PEDANT (GSF)
 * Protein Extraction, Description, and Analysis Tool
 * http://pedant.gsf.de/

 * PDBSiteScan (Institute of Cytology and Genetics SBRAS)
 * designed for searching 3D protein fragments similar in structure to known active, binding and posttranslational modification sites
 * http://wwwmgs.bionet.nsc.ru/mgs/systems/fastprot/pdbsitescan.html

 * (Centro Nacional de Biotecnolog&iacutea)
 * contact prediction server
 * http://www.pdg.cnb.uam.es:8081/pdg_contact_pred.htmlPDGcon

 * PIMWalkerTM (Hybrigenics)
 * intercative tool for displaying protein interaction networks
 * http://pim.hybrigenics.com/pimriderext/pimwalker/

 * PIVOT (Tel Aviv University)
 * Protein Interactions VisualizatiOn Tool
 * http://www.cs.tau.ac.il/~rshamir/pivot/

 * Protein3D Home (LECB)
 * http://protein3d.ncifcrf.gov/tsai/frame/main.html

 * Protein-Protein Interaction Server (University College London)
 * 3D structures
 * http://www.biochem.ucl.ac.uk/bsm/PP/server/server_help.html

 * SCOWLP (TU Dresden)
 * Structural Characterization Of Water, Ligands and Proteins
 * web-based relational database describing PDB interface interactions at atom, residue and domain level
 * http://www.scowlp.org/

 * SPIN-PP Server (Columbia University)
 * Surface Properties of INterfaces - Protein Protein interfaces
 * database of all protein-protein interactions in the Protein Data Bank
 * http://trantor.bioc.columbia.edu/cgi-bin/SPIN/

 * STRING (EMBL)
 * Search Tool for the Retrieval of INteracting Genes/proteins
 * database of known and predicted protein-protein interactions for a large number of organisms
 * interactions include direct (physical) and indirect (functional) associations
 * data are derived from four sources: genomic context, high-throughput experiments, (conserved) coexpression and previous knowledge
 * http://string.embl.de/

 * YETI (University Edinburgh)
 * Yeast Exploration Tool Integrator
 * workbench tool for visualization/analysis of post-genomic data sets available for Saccharomyces cerevisiae
 * http://www.yetibio.com/


text:
Talk:Circuit Idea/How to Make the Simplest Transistor Amplifier Bipolar

Here is the building "scenario" that my students (group 66a) and I were using during Lab 3 to consider the great biasing idea. Circuit-fantasist (talk) 07:15, 28 April 2008 (UTC)

Lab 3: Biasing the simple common-emitter transistor amplifier
Tuesday, April 01, 2008, 13.45 h

Building the circuit on the whiteboard

Making biasing batteries

Mounting the circuit on a prototyping PCB

Investigating the circuit by Microlab

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Talk:Circuit Idea/Reinventing a Full-Wave Bridge Rectifier

Here is the building "scenario" that my students (group 64a) and I were using during Lab 3 to consider the popular diode circuit of full-wave bridge. Circuit-fantasist (talk) 07:18, 28 April 2008 (UTC)

Lab 3: Building a full-wave bridge circuit
Thursday, April 03, 2008, 13.45 h

Participants of this lab: Andrey Rachev, Ivelin Ivov, Ivaylo Katrazanov, Rumyana Naydenova, Sasha Madov, Miodrag Hristich, Andon Radulov, Galin Gyurov, Kamen Avramov, Dimitrina Nedelcheva, Slavka Petrova, Zdravko Georgiev, PavlinPanev 64, Ivaylo Atanasov and Miglena Nesterova.

Investigating an LED

In this exercise, we have recreated the famous circuit of full-wave bridge. In order to visualize its operation (where currents flow), we have decided to replace the ordinary rectifying diodes by LEDs with different colors. Also, we have used another LED for a load. Firstly, we have investigated the very LED to make ourselves familiar with its behavior. We have found that its performance is good for our purposes, it would shine and work without problems. It was clear that we had to connect a protecting resistor in series with the bridge circuit. PavlinPanev 64

Building the circuit on the whiteboard

Step 1. We started building the circuit on the whiteboard by connecting the load (the tested red LED). Here we assumed that DAC 1 was producing a positive voltage from 0 up to 10 V (this was the positive half-wave). Note how we have outlined the inverse S shape of the "positive" part of the future bridge. PavlinPanev 64

Step 2. Then we assumed that DAC 1 was producing a negative voltage from 0 up to -10 V (this was the negative half-wave) and connected the true S shape of the rest "negative" part of the future bridge. Only, a short-circuit turned out:( What should we do then? We began thinking... We had already known that diodes can act as decoupling elements (switches); so, we put two red-colored LEDs in the two opposite "positive" bridge legs acting as rectifying and visualizing diodes for the positive half-wave. We expected that since all the three diodes (including the "load") were connected in the same direction they would enable the current to flow in the right direction and would shine during the positive half-wave.

Step 3. But it was not sufficient...:( To remove the conflict, we had to put further two (now, green-colored) LEDs in the two opposite "negative" bridge legs acting again as rectifying and visualizing diodes for the negative half-wave. We solved the short-circuit problem; we managed to "invent" the famous full-wave bridge rectifying circuit!

You can see on the picture how we made the full wave bridge – never mind if the current flows from –  to  +  or from + to -, our red load LED will always shine! Now we can carry out a real experiment to see if our circuit will really work. PavlinPanev 64

Mounting the circuit on a prototyping PCB

This was a true hands-on exercise where we mounted the real circuit on a real prototyping PCB; we soldered the two rectifying LEDs and the LED load on the board and connected them by wires. Thus we finally got a real full-wave bridge rectifier that didn't need any measuring devices. Imagine it should indicate its state (the current direction) by the very diodes! We were eager to get to know, if it would work really as we had assumed? It would be very interesting to test it. PavlinPanev 64

Investigating the circuit by Microlab

After we supplied the circuit by Microlab system we were ready to investigate the circuit operation.

Positive input voltage

It was working as we expected - the three red LEDs were lighting when we put a positive input voltage, the other two LEDs were extinguished. Everything was OK, as we wanted to be. User:PavlinPanev 64

Negative input voltage

Then we tested the circuit at negative input voltage; again the result was excellent as we had expected. We were content with ourselves as we did our job very good. The famous full-wave bridge was working not only in theory but in real! PavlinPanev 64

 * PavlinPanev 64, thank you for your participation. Your text is very useful and informative; what you write is exactly what we need for this page. Go on developing the page in this way. Place four tildes after your insertion (they will be replaced by your user name and the date of the creation). I have also placed some photos on your user page; you have only say some words about yourself. Regards, Circuit-fantasist (talk) 05:16, 25 April 2008 (UTC)


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Talk:Circuit Idea/How do We Build the Simplest Transistor Amplifier?

Here is the building "scenario" that my students (group 65a) and I were using during Lab 3 to consider the simplest common-emitter transistor amplifier. Circuit-fantasist (talk) 07:22, 28 April 2008 (UTC)

Lab 3: Building a simple common-emitter transistor amplifier
Tuesday, April 01, 2008, 10.30 h

Building the circuit on the whiteboard

Mounting the circuit on a prototyping PCB

Investigating the circuit by Microlab

Revealing the circuit imperfections


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Talk:Circuit Idea/Building an Emitter Follower

Here is the building "scenario" that my students (group 67a) and I were using during Lab 3 to consider the famous transistor circuit of emitter follower. Pay special attention to this work as it is entirely made by the very students. Circuit-fantasist (talk) 07:27, 28 April 2008 (UTC)

Lab 3: Building an emitter follower
Tuesday, April 01, 2008, 16.45 h

authors: Angel,Virginia & Vladimir

Looking for analogies of negative feedback phenomenon
Speaking. We are getting started with an explanation of the term negative feedback. The first thing we ask each other is if there is a similar phenomenon in real life. Thus we have found we might consider human speech as an example: you have to listen to your voice in order to control its volume. In this way you are able to communicate with those around you appropriately. The noisier the surrounding environment is, the louder your voice becomes and vice versa. This basic idea explains roughly the essence of negative feedback.

Driving. Another example of the idea of negative feedback might also be the following situation. Imagine you are getting in your car and striving to drive with 50km/h. Let us now suppose that we have a current state X and we want to achieve another goal state Y. In order to complete this task we should monitor the process of its development and control it in a desirable way by adjusting all necessary parametres. You are in state X and you would like to achieve state Y. But what do you need?

Generalizing the analogies into a block diagram
The first thing you need is ENERGY. It's necessary but not enough. You need also a visualization of your speed in order to control it. In other words you need a REGULATOR.

But what is the regulator doing? It compares the difference between the purpose state and the current state; then, it does what can do to eliminate it. When this difference is equal to zero, we have an equilibrium – this shows that the goal state has been achieved.

Building an electrical follower
The most simple regulator is the so called follower. Now we have to think about how we can realize a follower.

Is the humble wire a follower?
An obvious example of electric follower is... a simple wire (?!?). This remedy is simple: if you want the potential of point B to follow the potential of point A, just connect them to each other by piece of wire. But is that wire a perfect follower? The answer is “no”. We will provide reasons why with the next example.

The wire as you know has its own resistance. Let us now connect a resistor (1 ohm), our wire (1 ohm) and a voltage source(10V) like it is shown in the second picture. After measuring the output voltage we see that it has been reduced with the voltage drop caused by the wire’s internal resistance. The reason for this is clear – the current flowing in the circuit.

Building an emitter follower on the whiteboard
So we decide to make use of another (this time more “perfect”) regulator – an emitter follower. Having already come to the idea of constant regulating and adjusting a desired value according to the changes in its environment, we proceed with a real scheme with a transistor. The transistor here acts as the regulating element of the negative feedback follower above. The essence is that it “observes” the potential in point A and changes the potential in point B (by changing its own resistance) so that to keep an almost zero difference between them. But let's give a description of our practical laboratory exercise.

Putting the powerful idea into practice
(How our laboratory exercise passed over)

Preparation. In order to reveal to us the "secrets" of ubiquitous transistor, our teacher Cyril Mechkov provided us with the opportunity to build our own test circuit and observe its behaviour. As curious students who usually enjoy taking things apart, we were desperate to "invent" our own emitter follower and get a preconception of the so called negative feedback. We already knew some of the basic applications of the transistor having already studied digital circuitry but most of us lacked any practical experience. Having realized that, firstly prof. Mechkov briefly outlined the idea of the laboratory session and then gave us a soldering iron, a test board and all the necessary equipment to carry out the investigation of our device. The old Apple II based PC proved ideal for the experiment - it not only served as a power supply:) but together with the MicroLab system was able to "watch" our scheme and draw real-time voltage diagrams. Armed with this powerful "weaponry" we felt like real inventors!

Investigation. Some of the girls were terrified when Miroslav (a colleague) switched on the scheme, but fortunately nothing exploded;) Everything was well under control. After connecting our newly constructed emitter follower to the prototyping board we started the investigation by gradually varying its power supply (ranging from -10 to 10 Volts). As you can see from the pictures in the region of the positive values the transistor's behaviour coincides with theory. The voltage drop of the emitter-base junction always "strives" to remain the same - exactly 0,7 Volts. In accordance with Kirchoff's laws the potential of the output emitter was just like we expected - the input voltage minus the voltage drop. By analogy, the same linear dependency was observed in the negative input range. The lab results in that case are reproduced in the picture below.

Problem. However, quite unexpectedly we suggested double-checking the scheme by connecting an old-fashioned analogue votmeter in parallel to the digital VOM. Miroslav then attached one of the crocodile clips to the emitter and the other to the ground of the board (notice that the emitter - collector power supply is bipolar). At first, the new result on the screen seemed quite strange - in the negative region there was a section with a constant potential. Something had made the emitter base junction reverse biased. Professor Mechkov smiled being aware of the "mischevous intruder" in the voltage diagram but wanted us to find out the cause. We didn't hesitate for long and changed the old-fashioned voltmeter with a Chinese 3$ one.

Voila! The key to the "mystery" was finally discovered - the reason for switching off the transistor was the voltmeter's internal resistance. In the case of the old electromagnetic device it was about 20 kOhms. This internal resistance had become the main reason for the advent of a current flow through one of the power supplies, our load and the voltmeter. This newly appeared current kept the potential at the output unchanging when the base supply was low enough (see the picture). We realized the n-p-n transistor can only "source" current; it can't sink current.

Strengthening the problem. Having discovered this effect, we decided to replace the voltmeter with a lower resistor (100 Ohms) in order to simulate a voltage breakdown through the reverse biased base-emitter junction. In that particular case the transistor acted like a zener diode stabilizing the output voltage in certain ranges. A reproduced PC based simulation is shown on the last picture.

Conclusions
'''The final conclusion from the laboratory exercise was that a simple emitter follower might not be so simple and predictable in certain situations. We gathered some really valuable experience by observing the changes in our transistor's behaviour - at first it acted as an emitter follower, then it became a zener diode finally it turned into a voltage controlled switch. The small transistor was like a skilful magician but one playing tricks with current. Electronics is really fascinating, isn't it!'''

 * Angel, Virginia and Vladimir, thank you for your participation! Your material is excellent; it is so fascinating, captivating and funny! It was a great pleasure for me to join your team and to do my best to refine your work. Thank you again! Circuit-fantasist (talk) 17:57, 14 April 2008 (UTC)


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Talk:Circuit Idea/How to Make a Transistor Switch

Here is the building "scenario" that my students (group 68a) and I were using during Lab 3 to consider the popular circuit of transistor switch. Circuit-fantasist (talk) 07:31, 28 April 2008 (UTC)

Lab 3: Building a transistor switch
Katerina Slavova, Tsarina Penkova 65gr, Eleonora Todorova, Radoslav Danchev, Hristina Malakova, Elena Hristova, Lubomir Nedyalkov, Pavlin Stoyanoff 64, Dimitar Petkov, George Gizdov 65, Ahmet Karaman 68, Alper Mutlu 68, Tamer Aydin 68, Maria Georgieva 65 and Kiril Keranov.

Thursday, April 03, 2008, 16.45 h

The history of the transistor
"The Transistor was probably the most important invention of the 20th Century, and the story behind the invention is one of clashing egos and top secret research."

The problem started in the 1907 when the AT&T (American Telephone and Telegraph) faced the competition erupting from the expiration of Alexander Graham Bell's telephone patents. And the solution was transcontinental telephone service. In 1906, the eccentric American inventor Lee De Forest developed a triode in a vacuum tube. It was a device that could amplify signals, including, it was hoped, signals on telephone lines as they were transferred across the country from one switch box to another. AT&T bought De Forest's patent and vastly improved the tube. It allowed the signal to be amplified regularly along the line, meaning that a telephone conversation could go on across any distance as long as there were amplifiers along the way. But the vacuum tubes that made that amplification possible were extremely unreliable, used too much power and produced too much heat.  After the end of World War II, a team of scientists was collected to develop a solid-state semiconductor switch to replace the problematic vacuum tube. This team included a mix of physicists, chemists and engineers. On November 17, 1947, Walter Brattain, an experimental physicist who could build or fix just about anything, made an experiment into a thermos of water. The silicon contraption he'd built was supposed to help him study how electrons acted on the surface of a semiconductor. The wet device created the largest amplification Brattain had seen so far. By turning on a positive voltage he increased the effect even more; turning it to negative could get rid of it completely. It seemed that whatever those electrons had been doing on the surface to block amplification had somehow been canceled out by the water - the greatest obstacle to building an amplifier had been overcome. Unfortunately this giant jump in amplification only worked for certain types of current - ones with very low frequencies. That wouldn't work for a phone line, which has to handle all the complex frequencies of a person's voice. So the next step was to get it to work at all kinds of frequencies.  In fact the device worked as if there was no oxide layer at all. And as Brattain poked the gold contact in again and again, he realized that's because there wasn't an oxide layer. He had washed it off by accident. Brattain was furious with himself, but decided to fiddle with the point contact anyway. To his surprise, he actually got some voltage amplification - and more importantly he could get it at all frequencies! The gold contact was putting holes into the germanium and these holes canceled out the effect of the electrons at the surface, the same way the water had. But this was much better than the version that used water, because now, the device was increasing the current at all frequencies.  Brattain had managed to get a large amplification at some frequencies and he'd gotten a small amplification for all frequencies - now he just had to combine the two. He knew that the key components were a slab of germanium and two gold point contacts just fractions of a millimeter apart. Walter Brattain put a ribbon of gold foil around a plastic triangle, and sliced it through at one of the points. By putting the point of the triangle gently down on the germanium, he saw a fantastic effect - signal came in through one gold contact and increased as as it raced out the other. The first point-contact transistor had been made.  He showed this little plastic triangle at a group meeting on December 23. It was official - this tiny bit of germanium, plastic and gold was the first working solid state amplifier. (The text is written by Radoslav Danchev)

Transistor as an amplifier

The first part of this laboratory exercise was to build a transistor switch on the whiteboard. And we started with a conversation about the behavior of the transistor. The lecturer asked us what are the real functions of a transistor and what a transistor consists of. Those who knew it were just few. What we knew from the previous year was that the transistor amplifies electrical current. But in the exercise we took a deep look in its structure and understood that the transistor is nothing more than electrically driven resistor. Actually there is no real amplification. The real function of a transistor is to regulate not to amplify. (The text is written by Radoslav Danchev)

In laboratory classes we imagined transistors the way they are normally explained in electronics - like a variable resistors. They are electrically-managed resistors, known as active transistors. Normaly, the voltage across the transistor would increase its value, but actually it fades. The transistor decreases the supply voltage. It seems that the transistor can regulates it - this is one of the main funcions of transistors.

Making transistor act as a switch
After discussion of what is transistor, we started talking about the meaning of the transistor switch. We concluded that this is an element with two states - OFF and ON. When the switch is off, no current flows through it, and therefore the transistor is off. The depletion region across the emitter-base junction is large. There is no potential differences between the base and emmitter. The emitter-collector terminals act as open. The second state is ON - then the transistor turns on as hard as it can. A voltage is present across the base-emitter junction. The depletion region across the emitter-base junction shrinks as much as possible. Here is a presentation about transistor switch : http://www.wisc-online.com/objects/index_tj.asp?objID=SSE3703 It is very interesting! Take a look!

Eventually, we understood what exactly transistor and transistor switch are, along with their general purpose. So we started building one. The building scheme is in the photo. Hristina Malakova68 (talk)

Assembling a transistor switch by simpler converters

 * Here are some questions about the circuit of the transistor switch. What does the base resistor RB actually do in this circuit? Can we apply 1000 V or even more to the transistor switch input? What does the collector resistor RC actually do in this circuit? A tip: present the transistor switch as a circuit composed by three converters (a voltage-to-current, a current-to-current and a current-to-voltage converter). See the pictures below. Circuit-fantasist (talk) 14:32, 20 April 2008 (UTC)

Mounting the circuit on a prototyping PCB

The picture above shows how we have built a transistor switch. It was very interesting task for us. Some of my collegues took part in this. I watched them with extreme attention. First, the lecturer found a prototyping printed circuit board (PCB), which he gave to us. After that we started building up our "invention". We soldered the supply voltage to the PCB. Then we put n-p-n transistor on the board. It was very difficult to solder its pins... but we made it!

Investigating the circuit
Then we put a lamp to use it like a collector load. The lamp had current charge of 100mA. We attached a button to control switching on and off the lamp. We soldered the button between the plus of the supply and the base of the transistor. When the lamp is off then the button is off, too. The transistor in this case is cut off. We attached also a contact point where we could measure the output (collector) voltage of our transistor switch. This was the final touch we made on our "invention". Our transistor switch worked very well and we tested it a couple of times. It was quite amazing. It was worth doing it.

Drawing conclusions
Finnaly we concluded that if we want our transistor switch to work properly, we have to observe some circumstances:

 * 1) The transistor must be saturated very well. Otherwise it would start warming up.
 * 2) If Rb isn't small enough, the transistor would be blocked and it would start warming up. Its behavior would be like an amplifier.
 * 3) The transistor must be in its two final states - saturated (fully ON state) or cut off (OFF state).

Hristina Malakova68 (talk)


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Talk:Circuit Idea/How Does an Active Follower Behave when Disturbed?

Here is the building "scenario" that my students (group 64b) and I were using during Lab 3 to reveal the unique property of the series negative feedback circuits to overcome all kinds of disturbances. Circuit-fantasist (talk) 07:45, 28 April 2008 (UTC)

Is the real diode a perfect component?

A forward voltage drop VF appears across a real diode when a current flows through it... What is this voltage drop - useful or harmful? Sometimes it is useful; other times it is harmful...

"Useful" examples. When we make voltage stabilizers, we need this voltage drop. In these cases we do all that is possible to create and increase this useful voltage drop appearing across various diode component: diodes, LEDs, zeners, multiple diodes connected in series...

"Harmful" examples. In other cases, when we use a diode as a switching element, we do all that is possible to remove and to remove this harmful voltage drop... Then we need an ideal diode without forvard voltage drop VF...

Making the simplest series diode rectifier

Deriving the basic idea from our human routine
(write here all the situations in your daily routine where you have remove all the obstacles standing in your way:) Circuit-fantasist (talk) 07:33, 27 April 2008 (UTC)

Implementing the powerful idea into an electrical circuit

Making an almost ideal "op-amp" series diode rectifier
What can act as a varying voltage source in our electronic circuit? What can "help" the imperfect diode by adding so much voltage to the input voltage as it loses across the diode? At last Lab 3 we were using transistors for such a purpose; let's now, for the sake of change, use an op-amp...

Now the op-amp has to "insert" the "helping" voltage VF into the circuit; so, how to connect it?

Eureka! We have invented an (almost) ideal diode without (any) forvard voltage VF! Let's investigate it by Microlab system.

...multiple diode voltage drops...

...battery voltage...

...resistor voltage drop
With the same success we can overcome the "harmful" voltage drop across a resistor. What a circuit can we "invent" in this way? Write its name here.... (reifilpma gnitrevni-non:)

Application. Now look at the old fashioned laboratory power supply that has helped us to carry out the famous Ohm's experiment. In addition to the positive and negative terminals it has also two mystic terminals named NFB. What are they? Why and when do we need them? Describe here and draw a picture about a possible application of this arrangement. By the way, when I was student and then young engineer, I have managed to burn out a few costly microchips when I was trying to supply them:((( What do you think, how have I managed to do that "heroism"? Circuit-fantasist (talk) 08:25, 27 April 2008 (UTC)

Making the harmful voltage drop act as an input

Resources
Strange things can be put into feedback loop a cheerful animated story (after Tom Hayes's Student manual for the art of electronics).

<<< top - Group 64a - Group 65a - Group 66a - Group 67a - Group 68a - page stage >>>

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User:Kiensvay

I am khmer Wikipedian.

km:w:User:Kiensvay

title: User:Kiensvay


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Talk:Circuit Idea/Simplest Transistor Current Source

Here is the building "scenario" that my students (group 65b) and I were using during Lab 3 to build the simplest transistor current source without feedback. Circuit-fantasist (talk) 07:58, 28 April 2008 (UTC)

Lab 3 (Group 65b): Building the simplest transistor current source
Tuesday, April 08, 2008, 10.30 h

What a current source is

We begin our lab with general questions: "What is a current source? What do we want it to do?" How does a current source behave? How do we figure out that some device is a current source? How do we make a current source?" Simply speaking, we have to form a notion about constant current source.

What have you known about the current source from the basic course of electricity? Here is the well-known symbol of a current source (see the picture). How to make a good guess that it is a current source? If I give to you a (black) box with two leads and I say that it is a current source, how do you convince yourselves that it is really a current source? Vladimir: It will begin warming... Why do you think so? And what will happen, if we connect the two leads (a short circuit - case 1 on the picture)? Is it dangerous for the current source (comparing with a voltage one)? Vladimir: Yes, it is... Atanas: No, it isn't... Indeed, there is nothing dangerous for a current source, if we short its two leads. As the current source is designed for a given current, it keeps up (limits) the current thus protecting itself.

Then, maybe the opposite condition - an open circuit (case 3 on the picture) - will be dangerous as the current source will try to pass the same current as before. In this situation, the current source is misled: it doesn't see the open circuit; it "thinks" there is something connected there. It just "sees" that no current flows and raises its internal voltage up with the "hope" to pass a current through the harmful "thing". Of course, the current source does not manage to pass any current through the open circuit and reaches the final (compliance) voltage; a saturation and even a breakdown occurs. Thus, the compliance voltage represents the maximum voltage that the current source can reach when strives to produce the desired current.

Passive current source

Atanas has said that, if we connect a resistor in series to the voltage source there will no problem with the short connection. Well, let's place a resistor; thus we obtain the simplest current source. Choose for concreteness the favorite pretty values for the electrical quantities: V = 10 V and R = 10 kΩ to obtain I = 1 mA.

Ideal load. First, make a short connection at the output of the circuit. Since there is no voltage drop across the load, all the input voltage V is applied across the resistor R. As a result, the current is exactly as Ohm's law says:

I = V/R = 10 V/10 kΩ = 1 mA

Keeping a constant current by using an ideal current load Passive voltage-to-current converter (Voltage causes current)

Imperfections. What are the problems of this humble circuit? Let's connect a load having some resistance to see what happens. As we can see, a voltage drop appears across the load and the current decreases.

The real load introduces some voltage drop VL, which affects the excitation voltage VIN. Now, not all the input voltage is applied across the current-setting resistor R but only the voltage difference VIN - VL. In other words, here the voltage difference VIN - VL determines the current IOUT instead the voltage VIN. As a result, the current decreases:

IOUT = (VIN - VL)/R = VIN/(R + RL)

This passive circuit is imperfect; it can't stand against the load "intervention" especially, if the load varies. It is a static, fixed, non-adaptable circuit... What do we do then?

Keeping a constant current by depreciating the load Passive voltage-to-current converter (voltage-controlled current source) Op-amp circuit builder (go to Stage 2 of this interactive flash movie)

Dynamic current sources
What a new idea might arise now? Let's begin reasoning... The problem pops up when we connect a load and, what is worse, if we begin varying its resistance. Note the load may be not only a steady or varying resistor; it might be a capacitor that is charging, a diode (ordinary, zener, LED, base-emitter junction, etc.) or even a voltage source (e.g., a rechargable battery)... It is not so important what exactly the load is; it is only important that a voltage drop appears across the load and this voltage drop confuses things.

Basic "dynamization" idea
If we look around, we can see that most things in this world are changeable, adaptable, dynamic... According to this observation, we have to make our current source react somehow to the load "intervention", to resist to its attemption to lower the current. That means something inside the current source has to change, in order to compensate the disturbing voltage drop across the load. What can change in this simple electric circuit?

Varying (dynamic) internal voltage

Vladimir: We might change the voltage... Yes, it is the one possible solution. Vladimir suggests, if the voltage drop VL across the load begins rising, the internal voltage VVAR of the current source to begin rising as well in the same direction with the same rate so that the difference VR between them to stay constant. This is the first idea: dynamic current source with following internal voltage. Till when will this magic continue? Of course, until VVAR finally reaches the positive supply rail. After that point, our wonderful "voltage-dynamic" current source becomes an ordinary one.

Have you heard the legend about Baron Munchhausen that was using his own boot straps to pull himself out of the sea? Our circuit is just one possible implementation of Munchhausen's bootstrapping idea in electronics.

Is there a negative feedback here? No, it isn't. The varying voltage source follows blindly the load voltage; it does not "interested" in the magnitude of the current.

 * I am not sure if a coil can be treated as a way to "produce" dynamic voltages for keeping the current constant (at least temporarily). Or is there practical way of doing so in real circuits?
 * Thanks,
 * /bruin

 * Yes, an inductor behaves exactly as a dynamic voltage source that opposes the changes of the input (exciting) voltage source so that to keep the current constant. Both the time-dependent elements (inductors and capacitors) behave as opposing voltage sources; only, inductors oppose the input voltage in the beginning while capacitors - in the end of the transitional process. Circuit-fantasist (talk) 17:36, 4 June 2009 (UTC)

Varying (dynamic) internal resistance
Do you have another idea? What else can change in this humble circuit when the voltage drop VL rises and, as a result, the current lowers? Atanas: Let's vary the resistance R... Great idea! The resistance R is another attribute that can change to keep the current constant.

Actually, we have to make the current source change its internal resistance so that to keep a constant sum R + RL; as a result, the current I = VREF/(R + RL) will stay constant. Again, till when will this magic continue? If RL reises, R will lower until it becomes finally zero. After that point, our wonderful "resistance-dynamic" current source becomes an ordinary one.

Since the resistor R has the property to keep up a constant current, they name it current-stable resistor. Agin, is there a negative feedback here? No, it isn't. The varying resistor changes blindly its resistance; it does not "interested" in the magnitude of the current.

Since the resistor R has the property to keep up a constant current, they name it current-stable resistor. Let's realize this idea as it is simpler and more obvious than the idea of a dynamic voltage source considered above.

A transistor acting as a current-stable resistor

What electronic component has such a current-stable behavior? A student: The operational amplifier... No, no, it has to be a simpler element. Remember in this lab cicle we consider diode and transistor circuits; so, it has to be a diode or a transistor. A hint: the one has a behavior of a voltage source (more precisely, of a voltage-stable element); the other has a behavior of a current source (current-stable element). Well, which of the two behaves as a current-stable element? Of course, the transistor...

Well, let's then see why the transistor has such a behavior. You have already studied a subject about semiconductor elements; so, you have to know how it behaves. Do you have any reminiscence of it? What can a transistor do? A student: ...to amplify... No, it might sound paradoxical but the transistor does not amplify; it attenuates!?! The only thing that a transistor can do is to change its present resistance thus dissipating a power and, as a result, regulating the current through or the voltage across the load.

Here is an n-p-n transistor connected in series with a load RL and a power supply VCC. It is a three-terminal element (a triode) while a diode is a two-terminal element. A triode is too complicated for our reasoning:) so, we break down it into two two-terminal parts: an input base-emitter part and an output collector-emitter part. Each of them has an IV characteristic; now we are interested in the output characteristic of the collector-emitter part. Why they name it "IV characteristic"? Because we can do two things with it: to apply a voltage across it and to measure the current through it or to pass a current through it and to measure the voltage drop across it. Also, they name this curve output characteristic because it represents the output transistor's part. How does it look? Let's present the circuit operation graphically.

For this purpose, we have to superimpose two characteristics - one of the source and one of the load. First, let's draw the IV characteristic of the voltage source acting here as a power supply. What is it? It is a vertical line that is shifted with the magnitude of the voltage source VCC. Then, we have to show the presence of the load by inclining the line to the left according to the load resistance RL. The resulting curve represents an IV characteristic of a real voltage source having a voltage VCC and an internal resistance RL (they name it "load line"). After, we have to plot the transistor's output characteristic on the same coordinate system. The crossing point is known as an operating point; it represents the present magnitudes of the voltage and the current.

When we vary the load, the load line rotates and the operating point moves horizontally along the transistor's output characteristic. But why? How does it do this magic? What does the transistor actually do to achieve such an effect? Can someone explain? Let's try.

When we lower the load resistance the load line stands up; the transistor does the opposite - it increases its present collector-emitter resistance RCE (or just RT) so that to keep up a constant total circuit resistance. We may show RT by another line that begins from the coordinate system origin (the trick is to think of the present resistance RT as an ohmic one). So, this line will rotate around the origin and incline as well. As a result, the crossing point moves along a new almost horizontal line - the output transistor characteristic. This line is imaginary, unreal, artificial but we can see only this line; it represents the behavior of a current-stable resistor.

The text below is written by a student from this group:

The BJT transistor as a three-legged creater (??? Circuit-fantasist (talk) 12:28, 27 May 2008 (UTC)) looks much like a light switch (2 legs for IN and OUT, and one for the ON/OFF button), and basicly that's what it is - a switch. But this one here is like those fancy light switches with a rotating knob or even the more fancy ones - with a metal "touch-plate", which can be used to set a different light intensity in a continuous range by rotating the knob, or keeping your finger on the metal plate for a short time. But unlike these mechanically controlled switches, the transistor is an electrically controled one - on this scheme the output collector-emitter(C-E) current is controlled by the input base current or the base voltage, whichever suits us more.

So here comes the simple idea - if we apply a constant base voltage, we will set a constant C-E current. When the C-E voltage increases (e.g. due to decrease in voltage on the load resistor Rl) the C-E resistance will increase too (remember we set the C-E current to constant using a constant base voltage). So what do we get - a dynamic varying resistor which keeps a constant current flow. In short - a current-stable resistor. Which is exactly what we need in order to make a constant current source.

This behaviour is shown on the IV diagrams below. They can be explained as a mechanism with the I line acting as a "fixed rail", on which the crossing of the two "pivots" - Rl and Rt lines - point A slides. As we decrease the load (Rl that is) point A slides down the Rl line, up the Rt line, and to the right on the I line. This means that the transistor resistance increases, so the whole resistance of the circuit remains the same, and therefore the current flow remains the same. As we do the opposite - guess what - exactly the opposite things happen ;)

--V.konushliev (talk) 08:42, 19 May 2008 (UTC)

Building a simplest transistor current source on the whiteboard
''Please, read carefully this story. IMO, this is the fanciest and the most incredible story about a transistor circuit that I have ever seen on the web! What do you think about this assertion?'' Circuit-fantasist (talk) 05:55, 20 May 2008 (UTC)

Looks scary at first sight :) But none of the elements involved bites, and everyone has it's role.

 * Maybe, it looks scary because we have placed here the final, complete and perfect circuit solution? Maybe, we would build it step-by-step snapping every drawing on the whiteboard to show the circuit evolution? Maybe... Circuit-fantasist (talk) 05:37, 20 May 2008 (UTC)

In the middle, surrounded by a blue line is the "boss" of the circuit - the varying load resistor Rl. It's he who leads the concert, and the whole curcuit is built for him - to satisfy his needs and desires for constant current. The nameless resistor just beneath the boss is his "bodyguard" - just in case someone curious moves the slider of the "boss resistor" to its very end and try to short-curcuit the power source through the transistor.

Everything outside the blue line is the BJT current source itself - a whole team of elements working for the "boss". There's the "hero" of the curciut - the workhorse - the mighty bipolar junction transistor (BJT), who does all the dirty job (donkey work:) of keeping the constant current. Connected to its base is his "manager" (modern heros need to have managers), the varying resistor (potentiometer) P, who is basicly a varying voltage divider, and by the means of base voltage Vb tells the transistor what to do. In this case - using a constant base voltage the manager tells him to keep the current flow at a constant rate. The "manager" also has a "bodyguard" - Rb keeping the power source safe from short-curcuit's caused by someone playing with the potentiometer P.

Then there are our watchfull eyes - the voltmeter V2, used to keep an eye on the voltage drop on the load resistor (the boss), another voltmeter V1, watching over the voltage drop on the transistor's collector-emitter junction, and an ammeter, which gives us a sneak-peak on the current flow.

Last, but not least - the power source VCC, who brings the whole curcuit to life :) -- V.konushliev (talk) 13:22, 19 May 2008 (UTC)

Mounting the circuit on a PCB
It was easy so far but now we have to materialize the circuit on a prototyping printed circuit board. Can someone solder? If yes, please! Here are soldering iron and solder. How do we solder? Look at this links: 1, 2. You may use also various tools...

The transistor is n-p-n type packed in metallic body. The collector is connected to the body; so, you might measure the collector voltage by touching the body. You may supply the circuit by the computer or by an external power supply. What do you prefer? If you use the PC supply, there are two fixed voltages (+12 V and -12 V). Maybe, it is better to use the two varying lab supplies because we might provoke our transistor current source by varying the supply voltage. If you prefer, you might use a single power supply...

For our educational purposes it is preferable to arrange the elements in a similar way to the circuit diagram drawn on the whiteboard. For example, place the negative rail at the bottom and the positive one at the top; drive the transistor from the left and take the output from the right, etc. Now, let's make some photos..

What do we connect as a load? Let's it to be something varying - this 10 kΩ rotating "potentiometer" will suit us. Connect it as a rheostat (a two-terminal varying resistor). By the way, why the slider is connected to the one end? What is the idea of this connection? Also, as it is very likely someone to burn out it, connect a protecting resistor in series with the potentiometer.

How to set the input voltage? How to make a lower voltage by a higher one? Of course, by another potentiometer supplied by the same power supply (here it is connected as a real potentiometer).

Investigating the circuit...
In the beginning, we may draw and superimpose the current loops over the circuit diagram. Then, in order to measure the currents and voltages, we have to connect ammeters and voltmeters.

I have an idea for a syncrinised presentation - I will "move" the slider of the input potentiometer on the whiteboard; at the same time, you will move the real slider on the PCB. In the beginning, the input voltage is 0 V; so, no any base current flows. The transistor is "closed". Increase carefully the input voltage and look at the input transistor characteristic; imagine we walk along it:) At some moment, a current will begin flowing through the base-emitter junction and β times bigger collector current will flows through the load.

What happens, if you go too far? The transistor will saturate. So, we have to stay in the middle where the transistor operates in the active region.

What elements constitute our current source? These are all the elements excluding the very load, of course... Well, now we have to see, if it is a constant current source. How? We have to disturb, "provoke" it and to observe its reaction to our "intervention". But let's afford an opportunity to Vladimir to tell what has happened in the laboratory (he can do it very well). Circuit-fantasist (talk) 19:41, 27 May 2008 (UTC)

The text below is written by a student from this group:

Everything here is based on the simple law of Ohm $$R=V/I$$

...by varying the load resistance RL...
... we observe a change in V1 and V2, but no change in the ammeter. We're happy: the current flow is constant :) How did that happen?

When we increase the load resistance Rl so does its voltage drop, which can be seen on voltmeter V2 (logically simple - more resistance generates more pressure). As V2 shows an increment, V1 respectively shows a decrement (their sum represents the voltage of the power sourse Vcc). Since we made the transistor act as a current-stable resistor, it "senses" the decrement of the C-E voltage drop and obediently reduces its resistance, so the sum of resistances in the circuit branch remains the same. Therefore the current flow remains the same too.

When we decrease the load resistance, exactly the opposite happens (V2 shows a decrement, V1 shows an increment, the transistor rises its resistance, the sum of resistance remains the same, and so does the current flow).

...by varying the supply voltage VCC
...we observe the same pleasing facts: no change in the ammeter, although V1 and V2 show changes. We're happy again: the current flow is still constant :)

This time both the voltmeters V1 and V2 showed increments of voltage drops, with the increment of the supply voltage Vcc. The transistor again "senses" the change in voltage drop and rises its resistance. But if the transistor reacts the same way as in the case above, how does the current remain the same, if there is no change in Rl? The difference comes with the fact, that the "manager" of the transistor tells him to rise it's resistance even more, by applying a larger base-emitter voltage. Of course this is due to the fact, that the "manager", as a simple voltage divider, divides a larger voltage (Vcc), and therefore gives a larger result (Vbe). At the end, the sum resistance of the curcuit branch rises enough to compensate the increment in supply voltage Vcc and keep the current flow the same.

And again, with the opposite input (decrement of Vcc) the opposite phenomena is observed, but the result stays the same - constant current flow. A job well done by the BJT and it's "team" :) --V.konushliev (talk) 15:11, 19 May 2008 (UTC)

 * Vladimir, now I am realizing that I have misled you to some extent in this experiment. The circuit is not as correct as it seems. It would be more consistent, if we have made all the possible to make the input "manager" keep a constant voltage. Here we rely on the constant power supply; so, we shouldn't change its voltage. We should supply the potentiometer by another voltage source or replace the input voltage-divider circuit by a voltage-stabilizing one (e.g., by connecting a diode into the lower leg). This would be a prelude to the famous current mirror circuit (see group 66b and group 67b). Please, edit your explanation according to these circumstances.

 * Vladimir, I have a suggestion to. Would you contribute the Circuit idea story about the simplest transistor constant current source (and not only it)? Your writing style is unique; so, you might tell your lively story in a separate page as a different viewpoint at this famous circuit. Circuit-fantasist (talk) 06:46, 20 May 2008 (UTC)

Resources
Reinventing constant current source reveals the philosophy behind constant current source Understanding the simple BJT current source

Simplest?
I was surprised to see a transistor with 4 resistors, when the simplest transistorised current source is a tr with one resistor from Vcc to base. Maybe a rename is in order? 82.31.66.207 (discuss) 16:34, 24 July 2013 (UTC)
 * Yes, you are right.--Circuit-fantasist (discuss • contribs) 19:27, 10 August 2013 (UTC)


text: Wikibooks:Community petition

title: Wikibooks:Community petition


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User talk:193.63.61.35

Please stop vandalizing pages, you will be blocked. Ah3kal (discuss • contribs) 11:48, 31 January 2017 (UTC)

Blocked
You cannot edit for 1 month due to disruptive editing. You are welcome to contribute constructively when editing privileges are restored. You may appeal this action with a reasonable argument by adding the text below. --Atcovi (Talk - Contribs) 12:08, 31 January 2017 (UTC)

title: User talk:193.63.61.35


text: User talk:193.156.194.5

title: User talk:193.156.194.5


text: User talk:203.158.221.227

title: User talk:203.158.221.227


text: User talk:194.83.66.253

title: User talk:194.83.66.253


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Talk:Circuit Idea/Building a BJT Current Mirror

Here is the building "scenario" that my students (group 67b) and I were using during Lab 3 to build the popular circuit of BJT current mirror. Circuit-fantasist (talk) 13:22, 28 April 2008 (UTC)

Lab 3: "Inventing" a BJT current mirror
Tuesday, April 08, 2008, 16.45 h

A voltage divider sets the input current

A true diode sets the input current

Replacing the true diode by a base-emitter transistor junction

Drawing the diagram on the whiteboard

Building the circuit on a PCB

Investigating the circuit

Resources
How to Reverse Current Direction is another Circuit idea story about basic current mirror. Current mirrors is a popular exposition of the current mirror topic written by the well-known web author Tony Kuphaldt

<<< contents - Group 64a - Group 65a - Group 66a - Group 67a - Group 68a - page stage >>>

<<< Group 64b - Group 65b - Group 66b - Group 68b >>>


text:
Talk:Circuit Idea/NFB Transistor Current Source

Here is the building "scenario" that my students (group 68b) and I were using during Lab 3 to transmute an emitter follower into a negative feedback BJT current source. Circuit-fantasist (talk) 13:26, 28 April 2008 (UTC)

Lab 3: "Inventing" a negative feedback BJT current source
Thursday, April 10, 2008, 16.45 h

Transistor as a current-stable resistor

Comparison with a voltage-stable resistor

Building the simplest negative feedback follower

Building an emitter follower on the whiteboard

Mounting the emitter follower on the PCB

Investigating the emitter follower

Making transistor behave again as a current-stable resistor


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Talk:Circuit Idea/Misleading the Op-amp of a Negative Feedback Circuit

Here is the building "scenario" that my students (group 64a) and I were using during Lab 4 to transmute negative into positive feedback circuits. Circuit-fantasist (talk) 13:29, 28 April 2008 (UTC)

What negative feedback is

The idea of the negative feedback is to manage to keep the balance. The circuit with negative feedback actually takes the role of active regulating element – never mind what the resistance is it keeps this balance (what do you mean here? Circuit-fantasist (talk) 17:09, 27 April 2008 (UTC)). All that an op-amp tries to do is simply to act as a real thinking human being.

Look at the picture. The difference ∆V between the input voltage Vin and the output voltage Vout is applied to the op-amp differential input. The thing is that the op-amp tries to keep ∆V very close to 0 volts so that the op-amp compensates the difference. However it cannot be more than the voltage on the amplifier itself (what do you mean here? Circuit-fantasist (talk) 17:09, 27 April 2008 (UTC)). Hote that the op-amp does not take energy from the input voltage source to supply the load; instead, it uses its own power supply. The input currents are very low (nano- and pico-ampers); so, we can say they are voltage inputs.

The negative feedback follower just repeats the input value, no matter what the obstacles are. In this way, it acts as a real human being. PavlinPanev 64

General idea
What happens, if we make a mistake when apply a feedback from the output to the input of the subtractor and, as a result, it becomes a summer? In life this means to fool someone to do things in the wrong direction (for example, to do something bad instead to do something useful and v.v.). He/she "thinks" that he/she reacts in a proper way but actually he/she does exactly the opposite!

We can reproduce this situation in electronics, if we swap (usually, involuntarily) the op-amp's inputs. As a result, the op-amp is "disoriented"; like human beings, it "thinks" that it reacts in a proper way but actually it does exactly the opposite.

In this way, we can introduce the great idea of the positive feedback. It is extremely useful (for example, all the flip-flop RAMs are based on this powerful idea). PavlinPanev 64

Converting a non-inverting amplifier into an inverting comparator with hysteresis
Similarly, what happens, if we make a mistake when build a non-inverting amplifier swapping the inverting and non-inverting inputs? Let's try.

How to investigate the circuit

Investigating the circuit


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User talk:Shnizzedy

Welcome, Shnizzedy!

Come introduce yourself at the new users page. If you have any questions, you can ask there or contact me personally. I saw your edits in the x86 Disassembly book. You're right that empty sections probably don't belong there until they have some content. I will work on adding some content to the section on global variables today, although it will probably be a stub. If you have any expertise on that area that you could contribute, that would be awesome. --Whiteknight (Page) (Talk) 14:28, 28 April 2008 (UTC)

title: User talk:Shnizzedy


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Talk:X86 Disassembly

PDF Version
I've been trying to make a PDF version of this book. However, in programs I have used, the syntax-highlighted source code does not appear in the final PDF files. This means that all the source code snippets appear in the PDF as large blank areas. I have only tried a few free programs, nothing professional yet. Does anybody have a professional PDF creator tool which can fix this? --Whiteknight (Page) (Talk) 15:01, 28 April 2008 (UTC)

New PDF
I made a new PDF Version recently, the syntax is highlighted. --Dirk Hünniger (discuss • contribs) 08:37, 14 March 2013 (UTC)

Merge in of Reverse Engineering
Many pages of this book still need to be merged in or marked for deletion. If you merge a page, please mark it with now merged. -- Adrignola talk contribs 22:47, 16 April 2010 (UTC)

title: Talk:X86 Disassembly


text:
Hebrew/Introduction

Contenidos

title: Hebrew/Introduction


text:
Blender 3D: Noob to Pro/Realistic Eyes In Blender

Note: Some pictures are outdated.

Overview
NOTE: this tutorial is incomplete!

This tutorial will teach you how to effectively utilize textures and materials in Blender to create realistic eyes for characters. This tutorial will not teach you how to finish the eye. Because you did already learn that in previous tutorials. This tutorial was inspired by a great Maya tutorial in the Gnomon Workshop series by Alex Alvarez. My goal with this tutorial is to teach you how to get those same stunning results using Blender. Please check out Alex' tutorial as well, as it is very informative and covers more detail than I will be covering here. This tutorial assumes you know your way around the Blender interface and so I will not explain each key command as I go, but will instruct you in what steps to take and point out details such as key commands only when it seems relevant to do so. In addition, you will need some sort of image manipulation software, as this tutorial relies heavily on image-based textures, which we will be preparing outside of Blender. I will be using GIMP, but feel free to use Photoshop or whatever you're comfortable with.

 * 1) The 4 original Maya tutorials in video format []

OK, let's dig in...

Reference Material
Let's Take a moment to familiarize ourselves with the anatomy of the human eye. Do a Google image search and examine whichever diagram is to your liking. Now, you don't have to pay attention to every single feature, but do take note of the cornea, the iris, the pupil, and the sclera. These are the only parts that are visible to us when we look at a person's eyes, and therefore the only parts we will actually need to create. Many of the diagrams you find out there will be disproportionate, and so in order to know how large to make our features in relation to one another, it is best to view a large number of diagrams, a large number of eye photos, and also photos of plastic models of the eye, as plastic models tend to be truer to scale than 2D drawings. I also found a photo of a guy popping his eyes half-way out of his head. All of these together gave me a good feel for what the appropriate proportions are for a human eyeball. To some extent though, cornea size and sclera shape will vary on a person-to-person basis, so there is no precisely correct size, per se.

Building The Eye
Creating a UV sphere. 24 segments, 24 rings, and a radius of 1 is recommended. The top of the UV sphere will become the cornea of the eye. So now let's go into side view, in the orthographic view, and with the topmost vertex selected and proportional falloff enabled, grab and raise this vertex along the Z axis. Don't click to finalize the edit just yet - first we will use the mouse wheel to control how much falloff is going to be applied. This process can require some finesse and multiple adjustments until the bump of the cornea is anatomically correct. You will want to set the falloff shape to "sphere". You can also make 2 balls, like in the Pocedural eyeball tutorial, and let the iris bend inwards of the inner ball.

If you like you can use a Torus for the iris, this is difficult but fun to play with.

Below is a render of the curve I ended up going with. You can use it as a guide when modeling if it helps you. This is with a SubSurf of 3 applied, so keep that in mind.

Now, some people may prefer to use a NURBS sphere for the geometry of their eyeball. If you are comfortable with NURBS modeling, and texturing NURBS models, go right ahead. It will give you a smoother and more rounded eyeball. I prefer not to complicate things with NURBS when polys will do just fine, and am guessing most of you feel the same, so I'm sticking with polys. This does however bring us to the topic of the SubSurface modifier and how it will affect your eyeball. When SubSurf is applied to a UV sphere such as our own, it causes the previously spherical shape to become slightly oblong. In other words, the eye will become nearsighted. This is barely noticeable, but it does happen, as a result of the way SubSurfing affects a UV sphere. You could create a UV sphere with more rings to ease this if it bothers you. It looks fine for our purposes though, to be honest. See the comparison in the animated GIF below.

There is one last issue to address with regard to using a polygon-based eyeball. That is the small triangles that persist on the poles of the eyeball. These stubborn tris will remain and you will find that they result in an ugly and unnatural pinched effect when a specular highlight appears over the center of the cornea. Adding a SubSurface modifier will not make them go away. This didn't become apparent until after I did some texturing work and test renders, but I want to point it out to you now, before we get into all that. (See examples below)

Now repeat this process at the opposite pole of the eye (the optic nerve area).

We are now ready to begin texturing the eyeball.

UV Mapping
In Edit Mode, we will define the seams for our eye. Select the edges you want to mark as seams and type Ctrl E, then choose Mark Seam from the menu.

With all of your mesh selected, type U to unwrap. We can now see our unwrapped UV layout in the UV/Image Editor window. (For older versions of Blender, you might need to select UV Face Select mode to unwrap, but it's better if you download the latest.)

We will make the iris on another mesh so don't spent time on the cornea UV island.

Those two islands we see are the cornea and optic nerve area. We can move them out of our way by selecting any vertex on them and typing L to select all linked vertices. Then G to grab as usual.

Grab and move your straightened column of verts over to the left.

Constraining to the X axis, by typing the "X" key after you grab, is a good habit to get into while straightening these out.

Straightening out all of these vertices into a usable grid shape will take you some time so we won't do it that way. Having a rectangular grid will prove very helpful when we are texturing our eyeball. so we will use an Add-on for blender. You'll want to use Blender's grid as a reference and just align the rows and columns to it exactly. Yes, you can get it exactly aligned, since there is a snap-to-pixels feature, Click on snap-to-pixels in the drop-up menu in the uv/image editor header. (Don't move the 2 circles when snap to pixels is on cause that will ruin them.) You can scale the whole thing up later, once each row and column is evenly spaced. If you can, leave some space between your UV layout and the border of the layout area, if you "bleed" it to the edge, you may have texturing problems later. But you can scale it down later, so no problem. we will download the UV Tool from Daniel Banasik. A wonderfull free tool which can smooth an align the vertex loops to a beautiful grid with a little effort. The old method was aligning every single vertex 1 by 1 :(. Page of the tool []

Installing an Addon is very simple. If you've like me not installed blender but use a standalone version it's done in no time. All you have to do is put a folder or file in a folder blender is reading for add-ons.

Just download it and Unpack it. What you've unpacked is, most of the time, precisely what you have to put in the add-on folder. In the blender standalone version folder (if you don't use a standalone version of blender, it's Operating system specific how to place an Add-on.): go to the folder with the name of the Version Number (at my version it is 2.75)-> scripts -> add-ons. then put it here. Save your work and quit blender. Then restart blender and open your work. Go to User Preferences under File in the blender program header (the uppermost) and go to addons. Go completely down and open the details of: UV: uv_tool. Then click the checkbox: most right and you're able to use it.

Noob Note: Don't forget to save the user preferences.

If you, like me, love Disney-Pixar Movies you can recently download an Uncommercial (you're not allowed to earn money with it) free version of Renderman, the program Disney Pixar uses to render their movies. You can install it and use a third-party add-on (PR-man) to implement it in blender. But that will come in later tutorials.

How to use:

select the loop on the right side and click on align, do the same for the left. You can't do more than 1 loop at a time otherwise you'll go out of Edit Mode in the 3D View. Then go to 3D view put back in Edit Mode and go back to UV/Image Editor. You'll Also notice nothing has aligned. so do them loop for loop. Just select the loop and click on Align. It will be automatically placed correctly. Just move on till they're all done.

It's important to pay attention to which way the UV layout is facing. Chances are the top of the sclera region is actually what you will want to be the bottom. It doesn't technically matter which way it's facing, but you will probably want it to look intuitive when you are painting the textures.

You can check this by going to the 3D view (or having split windows so you can see the 3D and UV views at the same time) and making sure everything is selected, then deselect 1 vertex close to the optic nerve or the cornea. Back in the UV/image editor the vertex will disappear all connected edges and maybe more from your UV map, so you can work out how the map corresponds to the actual mesh surface.

Once you're done, save your .blend file and then save your UV Face Layout. This is done in the UV's: Export UV Layout.

Preparing A Template For Texturing
Now launch your image editor and open the UV face layout you just saved. (You probably saved it as a .png file, since that is Blender's default format for UV layouts) So we are now looking at a UV grid with the square and the 2 islands.

Open gimp and rescale the image to 4092 by 4092.

One other element that will be useful to have in our template is a layer of markers that denote where the equator of the eye is, because what looks like the middle on the UV layout is not actually the middle. To find the middle, go back into Blender and count the rings of your eye mesh, starting at the seam of the cornea. Once you get to the equator, take note of how many rings it took to get there. Go back to your image editor and mark that area. You can mark it with a guide, or mark it with a coloring of some sort - as long as it's clear to you that it indicates the equator of the eye mesh. It may also be useful to mark the point where the transparency of the cornea should begin.

Now we will make the texture. To begin make the inside of UV square and islands white, a neutral colour.

Do this by selecting (round or square) the UV island or square and then clicking 2 times on the bucket and set the Affected area to Fill whole selection then switch the black and the white colour by clicking on the arrows in the toolbox (If you've no toolbox click on tools in the program header and click: new toolbox) and click with the bucket on the selected area and do this for every part of the eye.

an eye is reddish at the back so make the back point directly reddish, I use FB2F05.

Select the back point so you can fill it with this beautiful colour.

Select the square so you cannot "Spill" over the corners. We will paint the back with the same colour of the back point 'till over the middle of the eye. click the airbrush tool and increase the value of the size and also the flow if its a very transparent at the end it has to be very transparent.

Noob Note: make the selection a little bit bigger then the square or the UV island to prevent seams.

Search for a nice iris texture: Make sure you have around 1024 by 1024 pixels.
 * 1) Google: iris texture []

Open with gimp and crop it out by pressing image -> Crop to selection save it as .png and use it later. If it's a little bit to small, don't worry you won't render it that big.

If you like you can make blood vessels in the cornea with the pencil tool and the colour FF0000. Make sure you shrink the to about 10. Only don't try to copy my vessels cause they are to bad.

You can design your own texture to apply.

Save your texture as .png.

Bump Map - The Sclera
If you want to use a bump map in your eye.

Create a material for your eyeball. Then within that material create a texture. Name this texture something like "BumpMap(Procedural)". Set the texture type to clouds. A noise size of 0.25 with a noise depth of 2 or 3 is fine, and you can experiment with other values if you like. The other texture settings can be left at their defaults.

Now we are going to bake this procedural texture to get an image-based UV texture that we can edit in our paint program. Why? Because there is not an even level of bumpiness around the eyeball. The sclera has bumps, while the cornea doesn't. If your cornea was bumpy, your vision would be distorted. We want our 3D eyeball to accurately convey this subtle difference when light is reflected from the surface.

Before baking the texture, there are some parameters we must specify. In the materials panel click the Map To tab. The Color button is depressed by default, so you can leave it as is. Make sure this is the only depressed button. Then change the color to black.

Now go to the Material properties. Change the diffuse color to white and click the Shadeless checkbox.

Note: In this particular case it doesn't actually matter which of these colors is set to white and which is set to black. The end result is basically the same, and you can always invert the image later.

Check the Material Preview window to make sure it looks right.

Time to bake your eye. Make sure your eyeball object is selected and go into UV Face Select Mode. Then split your screen and set one viewport to the UV/Image Editor. From the menu at the bottom of the UV/Image Editor, choose Image > New. Enter a name like "ScleraBumpBake" and set both the Width and Height to 2048 (to match your UV guide). Click "OK" and a new all-black image will appear behind the UV grid.

Go to 3D view then in the render properties to Bake and click Textures at the Bake-mode drop down menu. Then set the margin to 10 and click the BAKE button. You will see the black image in the UV/Image Editor fill in with your bump texture. From the menu choose Image > Save As Image.

Now save your .blend file. You are able to make the rest of the eye yourself and if you forgot, read to previous tutorials.