Designing a test rig

Other Hardware General Electronics
1

Hello all

A friend of mine has a PCB he uses 'out in the field' for controlling contactors etc
It runs on a 64 pin PIC IC I believe and has multiple analogue and digital inputs and outputs.

He has asked if I can come up with some way of testing these PCBs.

By this, he means for EMF noise, RF interference etc.

I can easily test the power rails and switching with an oscilloscope. Its the RF noise and EMF I am wondering about.

I asked him how he originally tested them and he said they basically set a noisy 230v contactor up and switched it on and off for a length of time, right next to the PCB.
That doesn't seem very conclusive!

Any ideas? I was thinking maybe a spark generator on a pulsed timer.

I will go a Googling...

2

  • I’ve used an old crapy electrical drill that exhibits contact arcing, not very scientific.
    :woozy_face:

  • An old Model T coil.

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3

That seems VERY conclusive, especially if a length of insulated wire was connected to ONE contact so it becomes a radiating antenna for the spark RF energy.

4

Remember to drive it at half speed, so you get little bit extra noise from triac.

5

You need specialised equipment to perform EMC compatibility tests.

If the board passes or fails the crude spark test , what conclusions can you draw ? Was it an unreasonable test ? Was the board susceptible ?

You need a faraday cage to check for emissions .
And ….
There no point in testing the boards , when fitted into an enclosure with other parts , the results can be very different .
Testing needs to be to recognised standards to be meaningful .

Tell him you can’t do it