Help needed in simple circuit design

[desmond]

I am currently designing a short circuit checker to verify the pins of a chip on a PCB.

there are totally 19 pins on that PCB and i would have to probe on those pins in on shot and find out which side by side pins are short circuit.

for example, pin1 and pin2, pin2 and pin3 and so on ..

i am only allow to use 5VDC power supply.

I would like to get some advise here .. how if i want to use LED to show indicate which pin are shorted, how should i design the circuit? what other component should i use?

Thanks in advance

 

[Russlk]

You want the sense voltage to be less than 0.5 volts so a diode is not detected as a short. Some voltage dividers and a comparator will do the job. Do you need a design or is this enuf info?

 

[desmond]

can i have the design pls? but i need to test 26 pins in one short to check out, means that it is something like a test jig, i put in the PCB and test the 26 pins in one short to check the short. Pls advise

Thanks.

 

[Russlk]

Ok, that is different than I first thought. If you are checking for shorts between pins in a "bed of nails" tester, you will need a micrprocessor and 26 analog switches. Apply a voltage, under 0.5 volts, to pin 1 and check pin 2. If pin 2 has voltage, there is a short. Next, apply voltage to pin 2 and check pin 3, etc., etc. I am not knowledgeable enuf in microprocessors to help further.

 

[desmond]

another question

harlow ..

if i am a voltage range from 0.6volt to 1.4volt ... how can i use this small voltage to turn on a LED? since the forward voltage in my case is around 1.8volt.

I would like to know for 0.6volt such low voltage, do i really have anyway to turn LED on? hopefully i can get your help in designing such circuit.

THanks alot ~

Desmond

 

[Russlk]

I am afraid that you need more help than I am able to give, sorry!

Try this URL:
Posted: Sun Apr 11, 2004 10:56 am Post subject:

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