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
Replies to This Discussion
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Permalink Reply by Jake Stew on -
Because of the magnet? No.
Because of shorts caused by sticking a big metal probe to a bare PC, yes.
[Post edited by moderators for civility]
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Permalink Reply by VIA UC on -
I don't understand what you mean by sticking a metal probe to a bare PC.
As you can see there is no physical contact between the sensor(the thing with the green cable) and any board (or anything for that matter besides the plastic frame).Please detail and thanks,
Levi
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Permalink Reply by VIA UC on
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I remember checking the Vin and had 4.2V. I'll check the GND now.
Thanks for the reply, Levi
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Permalink Reply by Jake Stew on
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The mods misspelled "PCB" and edited my post to remove my suggestion that you read some basic information on electronics, such as proper handling and esd precautions.
It is highly uncivil to censor someone by removing good and proper advice.
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Permalink Reply by VIA UC on
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First of all, you misspelled PCB and not the moderator, thus the confusion in my first reply.
I have also found your comment acidic and unhelpful.
I have made it quite clear that there was no contact between any of the PCBs and the sensor, re-asserting your opinion that they did touch is of no use to my problem.
If you would have wanted to help than you would have mentioned something specific, reading 'some' books is not what i consider to the point of this thread.
Keep smiling, Levi
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Permalink Reply by Richard on -
You've got a completely dry joint on the 328P debug/programming port.
Top-left of the photo, top left pin (VCC). It doesn't make contact with the PCB at all.
That might be why you can't connect to the 328P.
Looking at the rest of the pin headers in shot, quite a few of them look like they might also be partly dry (it's hard to tell from a photo).
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Permalink Reply by VIA UC on
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Indeed you are right Richard! The ring connector of the PCB had broken and fallen off on that side, however the actual connection to the 328P is on the other side. I have made sure that it is connected there.
I have also used the multimeter so make sure that each of the 6 SPI pins are connected to the microcontroler, that is for all of the 6 pins I get a 'beep' (meaning ~0 resistance) on the uC pins.
Thanks for the input, Levi
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Permalink Reply by VIA UC on
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In order to make sure that my programmer is working ok and the avr studio software is set up correctly I connected to the 2560 and was able to read it.
I then reconnected to the 328 SPI and got confirmed again that it is not working, unable to read device signature.
I saw that the 328p is similar(same) to the Atmega48pa microcontroler, which I happen to have one of.
The issue is that it's PDIP configuration. Has anybody tried to replace it a 328p TQFP with a 48pa-pu PDIP? Can anyone give some guidance on how to make the soldering if it is possible to use?
Also please state your input on the issue of the possibility of a magnet doing damage (in the situation mentioned in my first post) even if you don't can't help awanser to the questions above . The other students with whom I work on the project seem convinced for whatever reason that it was the magnet that made this mess. (and not the relay or something else) I would like my name cleared if it isn't my mistake after all.
Thank you and have a nice evening,
Levi
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Permalink Reply by Nick Arsov on -
Hi Levi,
If the outer metal ring of the magnet hasn't shortened some pins....the magnet is NOT guilty!
The solder spot marked with circle is not guilty too as it is over the GND. More, the solder mask protects the traces from such disaster.
So....think carefully what have you done step by step and place your memories here... ;-)
Best regards
Nick
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Permalink Reply by Jake Stew on
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The magnet couldn't do anything to your electronics. The amount of voltage and current induced by a nearly motionless magnetic field is infinitesimal.
The calculations are all to be found in a physics 1 or 2 textbook. If you want proof I'd just shove those calculations in their face and let them struggle to come up with the numbers.
http://en.wikipedia.org/wiki/Electromagnetic_induction
Lenz's law: The EMF induced in an electric circuit always acts in such a direction that the current it drives around the circuit opposes the change in magnetic flux which produces the EMF.
That said, I think you probably shorted something out by sticking a big metal probe to a bare, powered up PCB.
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Permalink Reply by Richard on
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The magnet almost certainly is not responsible.
It's a shame you didn't take a photo of the damage to the PCB before your fix.
Was it bent away from the PCB substrate and discoloured? (eg Green/blue)
If so, then it was a pretty big overcurrent.
I think the damage was caused by the LEDs that were added.
- My guess is that they were wired to return their current through the APM ground, instead of using the relay as a dry-contact as it is intended.
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Permalink Reply by VIA UC on
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I can always remove the solder if we think that that could shed some light on the problem.
At this point I will get a new 328p, replace it, and see what we got.
I'll get back then if no other suggestions are mentioned here.***NOT RELATED TO PROBLEM, CAN BE SKIPPED***
Regarding the closure part, I thought/knew that it's no way that the magnet caused this. I just got pushed into believing that.
THIS is the part I hate the most, when someone makes me doubt things I know and thus myself. It's one of the worst thing someone can do to me.
Thank you all for your inputs, Levi
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