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Help Fixing a Sanguinololu After Mistake

danfinlay

Help Fixing a Sanguinololu After Mistake
July 11, 2013 05:53PM

Registered: 10 years ago
Posts: 9

Looks like when soldering in some header pins I bridged a couple other pins! The rest of the board seems to work, so I just need someone familiar with Sanguinololu 1.3a to tell me what to jump to the appropriate pins.

Any help?

hRORwxJ.jpg

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danfinlay

Re: Help Fixing a Sanguinololu After Mistake
July 11, 2013 06:07PM

Registered: 10 years ago
Posts: 9

Looking at the Pololu pin guide here:

0J4345.600.png

looks like pin D is the GND for the microcontroller, while pin C is +12 from the power supply, so the short was actually between two different power sources. If this is right, I should jump the pololu pins that go to D and C to microcontroller GND and power supply +12 respectively.

Edited 1 time(s). Last edit at 07/11/2013 06:10PM by danfinlay.

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danfinlay

Re: Help Fixing a Sanguinololu After Mistake
July 11, 2013 06:55PM

Registered: 10 years ago
Posts: 9

Whether I jump A to C or leave them disconnected, when energizing there is an arc from C to D still, despite the charred remains. Here is a picture of the flare up:

Q2njgIW.jpg

and here is a macro photo of what is there:

VhTQJrv.jpg

Why is it flaming up?

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danfinlay

Re: Help Fixing a Sanguinololu After Mistake
July 12, 2013 03:41AM

Registered: 10 years ago
Posts: 9

I believe I found my answer here. It says:

Quote
R.G. Says:
PCB cancer.

No, not being funny. When a PCB starts arcing, it carbonizes a path under the arc. The carbon traces are conductive, so they keep conducting. If there is enough current available, it keeps charring and eating more PCB.

Whatever started it - perhaps a microscopic thread of copper left on the board, is probably gone by now. Could have been a defect in the original PCB material.

To stop this you have to interrupt the current path by cutting or scraping away any trace of charring to restore it to an open circuit.

I first ran into this when working on a 200A 5V power supply. Only there, the current had charred away about 2 square inches of PCB area.

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lajos

Re: Help Fixing a Sanguinololu After Mistake
July 15, 2013 09:52AM

Registered: 10 years ago
Posts: 180

It's hard to tell from the photos, did you have the stepper driver installed when the arcing happened? Or was it also burning without the stepper driver?