Project circuit design

Hey there,



I'm writing to you because I've ran out of idea for my project. I'm trying to build a simple open or short tester for both transistors & mosfets. If possible I would like to have, maybe some LED indicators to accertain good, short and open devices. It would be terrific if I would be able to simultaneously test, lets say 10 trs at once or by relay switching method. Do email me if you have any kind of solutions.



Your help is very much appreciated.



Thank you,

Seasons from Malaysia

I am not getting what exactly you are looking for. Please give detailed info.

Of course it is possible. You could use a resistor in series with the emitter/ source and make sure the transistor is biased in the active region (if it is good). Then you measure the voltage across the emitter/ source resistor. If it is too high, then the transistor is shorted. Too low a voltage indicates an open transistor.
You can then use relays to select which transistor is being measured at a certain time. A micro will most likely be required for this project.

Hi VVV,

I'm not so well verse in electronics. I would like the circuit to work on both bipolar transistors and mosfets. From your explanation, it seems like I have to use a measurement equiptment. Is it possible for me not to use it? It will be great if it is able to indicate the device is open, short via led indicators.

Is there any place I can refer to the circuit? Btw, what is a micro? Do you mean a microcontroller? I think I'll be having more problems as I don't know programming as well. Hope you can help me solve my problems.

Best regards

Yes, a micro is a microcontroller.

As for measurement equipment, no, that is not what I meant. You can simply have a couple of comparators with a good, stable reference, that monitor the voltage across the resistor while the transistor is powered. If the voltage is within certain limits the comparators will consider the part OK, otherwise it will be either open or short, depending on how high or low the voltage is.

This can work for one transistor. But if you want to measure more than one device at a time, then you need some "intelligent" device (a micro) to do the switching and keep track of what each device did, turn on the LED's, try between FETs and bipolars, reverese polarity, etc. So if that is what you want, then you will have to use a micro and program it. It may be chanllenging, but it is rewarding, too.

I suggest u build ur tester using any suitlable microcontroller like pic 16f877 because then it would be too easy to handle the user interface related stuff..