PCB traces tester

I need to create a test fixture for 18 traces on a PCB board, I need to send voltage to 2 traces at the time and light up an LED if we encounter a short between those 2 traces. There are 32 combinations of test applied to these 18 traces. If a short circuit is encountered I need to turn an LED to show the place of the 2 shorted traces and leave it on.
I will create an identical layout of the traces with an LED connected to each individual trace. So I need to shift the voltage around until I complete the test of all these traces. The complete board has 30 mini boards, each with 18 traces. At the end only the mini boards without any LED's ON will pass the test.

Could someone help me with some ideas on how to accomplish this? I was thinking on using a PLC (Programmable Logic Controller), but I am sure I could accomplish the same results with a different much smaller controller.


Which board(s) are you testing? The mini boards or the 'big' board?
Where does the 32 tests come from? There are a lot more possible combinations for 18 traces.

May we assume that the pcb that you're talking about is not yet populated witch components? If so

Why 'send' a voltage to two traces at a time? You can set one pin high ('send' a voltage) and next measure all other pins. If one (or more) is high, you have shorts. Next set the next pin high and measure all other pins; etc. etc (as you basically described).

Do a search for cable tester here on the forum; you might get some ideas.

Thank yo Sterretje,

I am testing all 30 mini boards on the big board one at the time. These are ceramic boards that after the test will be cut into 30 individuals boards. You are correct, I will only be sending voltage to one pin and read on the other. These traces are so close to each other that because the way the are manufacturing them, sometimes they fail to completely remove the metal in between and they of course are in short circuit mode.

There are actually 13 traces. 9 one next to each other and 4 all along the length of the 9, 2 on the top and 2 on the bottom, we need to test every possibility of contamination between all of them. The boards of course are not populated and the traces will be plated with gold.

My idea is to recreate a PCB board with the actual layout of the big board and use POGO pins to drop the big board on top and have all the pins wired to a controller or a PLC (last resort) where I can turn ON an LED to signal failure of the test on any particular mini board.

I hope I can find a controller capable of handling this project, I need a lot of Inputs / Outputs to test these boards.

You can set one pin high ('send' a voltage) and next measure all other pins. If one (or more) is high, you have shorts.

Hm. I think that is not true, the input is floating connected to an isolated (not shorted) trace,
you probably need pulldown resistors on the input pins to go that way.

Attached is a mini board layout, I have an arrangement of 5x6 in the main board for a total of 30 mini boards all together.

The test I need to do is between:


A/1 C/1 1/2
A/2 C/2 2/3
A/3 C/3 3/4
A/4 C/4 4/5
A/5 C/5 5/6
B/5 D/5 6/7
B/6 D/6 7/8
B/7 D/7 8/9
B/8 D/8
B/9 D/9

I can apply voltage to A and read all the A# points at the same time, and repeat with B, C, and D

Once I am done testing one mini board I have to repeat 29 times to completely test the entire board.

That is the main idea, I need to turn a RED LED to mark a bad mini board and location, just for that I need 30 outputs. I am not marking good mini boards.

I could use a PLC (Programmable Logic Controller) but if I can I would like to embed the controller in within the PCB layout that I am designing. That way I keep it as one board fixture, small and simple.

Board Test Fixture Model 1.pdf (14.1 KB)