Exploded BeagleBone

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a_huctwith
 
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Exploded BeagleBone

Post by a_huctwith »

I recently bought a BeagleBone Black, along with a power cord (5V 2A, the one suggested) from Adafruit for a robotics project. Today it arrived, and when I plugged it in (using the power cable) it made a crackling noise and began to emit smoke from under the edges of the SOC, and from the USB port. It also produced a burning plastic smell, and left two small spots on the SOC's plastic deformed. When I pulled my keyboard out of the USB port, the end of the cable was very hot, and it now does not work on my other computer. I am not entirely sure why this has happened, as the power cable is well within the limits of the BeagleBone, and I was incredibly careful to keep the board on top of the antistatic bag it came in. What should I do at this point?

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adafruit_support_bill
 
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Re: Exploded BeagleBone

Post by adafruit_support_bill »

Wow! Haven't heard of anything like that before. The Beagle Bone folks handle these kinds of problems directly. Please contact them at:
http://beagleboard.org/Support/RMA

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jgotthardt
 
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Re: Exploded BeagleBone

Post by jgotthardt »

It seems logical that packaging materials that protect a device during shipment will also protect it in operation, but this is not the case for anti-static packaging material. This material is conductive in order to prevent the buildup of static charges which could damage static sensitive components on the board. By placing your board on the conductive material you create many low impedance paths which can cause high currents to flow when power is applied. The higher than normal currents generate excess heat which can damage components.

That's the EE explanation. But now you know the real truth: electronic devices run on the magic smoke that is inserted during the manufacturing process and if you let the magic smoke escape the device no longer runs properly. Welcome to the club!

John

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adafruit_support_mike
 
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Re: Exploded BeagleBone

Post by adafruit_support_mike »

Anti-ESD films have a DC resistance in the gigohm range.. far too high to cause a component failure. Test a chunk of pink film or a silvered envelope with a multimeter and see if you can even get a reading.

IIRC, the average electrical spark has a voltage of about 3-10kV and an accumulated charge of about a nanocoulomb. There isn't much current, but the charge carriers really want to get from one place to the other. It only takes 1v to push 1nA of charge through a 1G resistor, and that would dissipate a nanocoulomb of fixed charge in one second. If you happened to acquire a charge with enough voltage to make a spark, it would dissipate in a millisecond or so.

Static electricity accumulates gradually, through three basic mechanisms: tribolelectric effects (electrons displaced by rubbing), photoelectric effects (much, much less power than solar cells, but does happen) and 'evaporation'.. electrons being (usually) carried away by air molecules blowing across the surface. All three happen gradually, so even 1G of resistance is practically a short circuit compared to their rates of accumulation.

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bmillier
 
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Re: Exploded BeagleBone

Post by bmillier »

It is true that the antistatic film envelopes have very high resistance, so it is unlikely an antistatic envelope could have caused the problem. However, the black antistatic foam that is used to protect ICs sometimes, does exhibit a low resistance- in the order of a few thousand ohms. You don't want to set a powered circuit on a sheet of this stuff.

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