Help needed in simple circuit design - Electronic Circuits Projects Diagrams Free

desmond · 5th April 2004, 02:43 PM

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 · 5th April 2004, 07:58 PM

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 · 5th April 2004, 11:32 PM

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 · 6th April 2004, 03:21 AM

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 · 12th April 2004, 03:35 PM

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 · 12th April 2004, 06:57 PM

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:

--------------------------------------------------------------------------------

_________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk or

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5th April 2004, 02:43 PM	(permalink)
desmond	Help needed in simple circuit design 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 __________________ Regards, Desmond

5th April 2004, 07:58 PM	(permalink)
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? __________________ see my website: www.geocities.com/russlk

5th April 2004, 11:32 PM	(permalink)
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. __________________ Regards, Desmond

6th April 2004, 03:21 AM	(permalink)
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. __________________ see my website: www.geocities.com/russlk

12th April 2004, 03:35 PM	(permalink)
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 __________________ Regards, Desmond

12th April 2004, 06:57 PM	(permalink)
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: -------------------------------------------------------------------------------- _________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk or __________________ see my website: www.geocities.com/russlk