Friday, April 26, 2013

Arduino Bot is hot... Wait, no.. IT'S ON FIRE!!

For 3 nights I stayed up till 3am trying to figure out the insane wiring on this thing and trying to get everything correct. Finally completed it today, typed in some sample code and get ready to test it.  I flip the switch,  The lights come on, a good sign... Then they all go out.  A couple seconds to see if anything is going to happen and....  Nothing.  Damn,  now I have to trouble-shoot and do more research. But wait,  what is that I smell?  Plastic burning?  Yep I smell plastic!  Now I see smoke coming from the wiring/mounting holes.  The power is off so what the heck?  I see more and more smoke coming from the motor compartment and can't get to it because I tightened all the cover screws!  A race to get the cover off and remove the batteries before the whole thing goes up.

The damage was limited to melting both the battery leads coating completely off and slightly melting the wires near them.   The battery leads were a very thing stranded wire, so when it shorted they acted as a heating element or even a fuse and burned up,  maybe saving the rest of the project!
Immediately checked the boards and they seemed to operate correctly. Then spent about 3 hours chasing the short.  Everything kept coming back alright but I finally managed to trace it to the 5 mm power plug that attached directly to the arduino.   Yes,  it is something I Soldered and looked great. Even tested perfect when the cap was off... But when you screw the protective cap back on, the voltage meter went crazy... The short was in the plug!
Swapped it out for a new one,  replaced damaged wiring and even a new battery case.
Moment of truth.... The darn thing fired right up and had even retained the test code we had programmed it with!   Works as it should, runs the simple driving/avoidance software. Hopefully there will not be any future damage to the chips because of the short.  But for now, it looks great.
Next step... Take a 5 hour nap!   Tomorrow I. Plan to start figuring out how to connect the Raspberry Pi directly.  Not so it downloads the scripts from the IDE, that's already done..  No,  we want to use the raspberry pi to run programs in Python and use the arduino to handle the physical part of the interface. The ardueno will run all the motors and sensors and the Raspberry Pi will not interrupt the sensor data and issue commands.   Hopefully!
Here's a couple photos of the charred battery box and wiring... What NOT to do.  I'm going to take a nap... Enjoy!
Pi Hard 

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