Circuitry ( 328p) fried due to magnet?

Hello,

Do you think that having a coin sized magnet, which is not moving,  will/can burn out cicuitery?

I was trying to do a vibrations measurement  using an accelerometer sensor which has a small magnet incorporated in order to achieve a better fix on ferrous materials.  I do know that it has MAJOR  effect on the magnetometer but that was not of essence.

The rig:

The magnet:

I made 3-4 small flights of a few seconds (~10) to get a feel of the copter then unplugged the lipo and went to make my measurement set-up at my laptop. When i connected the lipo a 'usual' spark was seen at the leads and the motors stared singing and I could not arm. I tried a reset/reflash firmware but it did not help.

I  saw via the mission planer that no radio signal were detected.

The APM board  power led did not light up and by pure luck found a small ripple in the circuitery and mended it whit a bit of tin.

After seeing that the radio inputs are all 0 I tried to connect to the 328p but I it cannot read it using avr studio. I think it's safe to assume it's fried as RC signal can be read with voltmeter at it's output.

I later found out that the Xbee module is also fried.

Can 328p be replaced or do I need to buy a new APM?


Can all of this happen because of the magnet? All my sensors are working fine (accel,gyro,magneto) and those should have failed first as they were closer and all imo. Also, as metioned, i did a few flights without any problems.

Can it be the spark that i saw when connecting the lipos?

I have also put some Leds on the wings and controled them using the relay and it was the first time i was fling with them on but I took care not to have any deisoleted wiring. I don't think that could have caused it, but it's worth mentioning.


It would be nice to know what happened  so it will not be done again.

Any suggestions on finding the problem are welcome.

Thanks, Levi

Tags: 328p, APM, PPM, burned, fired, magnet

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Replies to This Discussion

Permalink Reply by Richard on June 5, 2012 at 4:56am

There's no point removing the solder, any information about the failure will already have been cleaned away by the flux - that's what flux is for.

I would first check all the passives on the PCB (capacitors and resistors). If any of those are dead then a replacement 328 may be killed immediately.

Permalink Reply by VIA UC on June 4, 2012 at 4:59pm

I am having a hard time recognizing this ICP header you are talking about as I no loner have the APM at hand.

Permalink Reply by VIA UC on June 4, 2012 at 6:18pm

Yepp, from now on I will heed your warning regarding ESD, truth is I forgot about that.

I remember  seeing a video a few years ago on the making  of pyrotechnical materials, in which all employees were required to touch a big (grounded) metal plate when entering the facility. An error there may cost you more than a  propeller.

However, the ICP (thanks for clarifying ) only got soldered on now, after the malfunction so... damn it, I almost wish it was that.

________

I personally blame a butterfly I saw during that fateful day. I think it flapped it's wings harder one time and the disturbance rippled outward and changed the flow of Eddy currents in the upper atmosphere. These probably caused momentary pockets of high-pressure air to form which acted as lenses that deflected the incoming cosmic rays and focused them on the SRAM of the 328. This caused the flipping of a bit and, obviously, division by zero which lead to the well know situation. (xkcd.com/378/)

Either this or it was Occam's razor touching some pins...

Good night, Levi

 

Permalink Reply by Jake Stew on June 4, 2012 at 9:41pm

> all employees were required to touch a big (grounded) metal plate when entering the facility.

LOL!  Where I worked we had anti-static lab coats and shoe straps.  Every time we left the main floor or twice a shift we had to step on a plate and grab a set of handles that tested our coats and shoe straps.  People frequently failed and had to adjust all their gear and retest until they passed.  

Sweaty socks, wet floors, shoe dirt, worn straps, dirty coats, and all sorts of other stuff would make your resistance too high or too low and you'd get that damn beeping and have to go to the back of the line. 

There's no fooling around with IPC class 3 electronics!

Permalink Reply by Nick Arsov on June 4, 2012 at 10:12pm

Hi Levi,

Before replacing the MCU, first check the 5V LDO ( sot23-5 ). If it is dead, just desolder it and power the board with a stable 5V via the alternative circuit ( 5V-blob-polyswitch-schottky)....see the schematics - http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/IMU/ArduPilo...

Nick

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