Maybe two years ago I found this project.
http://www.youtube.com/watch?v=ux5gh4jGS3Qhttp://www.youtube.com/watch?v=PRjM9Kkg-xMand the svn
http://www.mikrocontroller.net/svnbrowser/transistortester/Its a german project, but I found a little english page with some infos and links.
http://dangerousprototypes.com/2012/01/23/avr-transistor-tester-build-2/and the original
http://www.mikrocontroller.net/articles/AVR-Transistortestervers. 1
http://www.mikrocontroller.net/topic/transistortester-mit-avr vers. 2
http://www.mikrocontroller.net/topic/248078#2709123This project has two versions. I have the first one. One layer and easy to build. The 2nd can't be much better, but I must say, I don't have read the whole 2nd thread, both are very long.
The reason for me to build it, was... it is cheap, easy, not more than 15 - 20 Euros and it checks much parts in secounds, without I know which part it is. And thats it ! Sometimes I have parts without any labels, or marks, or lables like "A1 23 xy" or in surface mount parts. You have no chance to check this, if you don't have any idea, what it can be. Or I search hours for hours in the web.
In one of Martins videos, he show you, how you measure a Transistor, a Diode, or a Z-Diode. Much much easier with this tester.
And the best. It tests Diodes, Z-Diodes, LEDs, BiPol Transistor, forward voltage with capacitance, FETs, JFETs, Resistors, Capacitors down to 35pF, even the pin assignment and more. I've not test it all

I think, it is an absolut "must have" tool. So check this out.
If anyone needs some help, I'am german and i try my best to help you.... with this school english
Special thanks to Markus Frejek (5volt)