I'm making a self-balancing robot using Arduino Nano V3, knock-off from ebay, and L298D to control my Pololu's 29:1 geared motors (http://www.pololu.com/product/1443/
) that has a stall current of 5A, and free running 300mA at 12V.
Recently, I screwup the battery that I had (12V, 1.8AH), by charging it the wrong way, so I decided to use a wall adapter to power up the robot (because I was too curious to test it).
I was in the stage of fine tuning my PID values before my battery died. Then I connected my wall adapter to the robot.
I was shocked to see my robot balancing on power from wall adapter on the same values. But that happiness lasted for only 20secs.
Since it was balancing, I decided to give robot a little push to make sure its working fine. But I don't know why, after two swings, the robot stopped responding to the accelerometer, and the motors were 'on' in their full speed (the motor directions were not responding).
Then I pulled out the wall adapter and plugged it in again, and voilaa, my Arduino died too
(Now when I connect that Arduino Nano to my computer, it detects the FT232R IC, but it can't burn any program.. And the ATMega328 gets very hot whenever I plugged it into any 5V, even from USB. So i'm guessing that ATMega328 died)
So, after a wonderful story
my question is, What could be the issue that my Arduino died? Can someone help me do the forensics, so that I be sure that it doesn't happen next time?
One more thing. I borrowed another Arduino Nano V3 (exactly the same) from a friend, burned the same code, and power it up from USB (not from wall adapter
). And the motors are working just fine (obviously, i'm not getting that speed and torque, I have to pick the robot up in the air to see the motors moving)
So from this, I realised that only Arduino died, not the motor controller.
P.S. I'm not using opto-isolators.
Here is the power scheme that I'm using:
1. Wall Adapter / Battery --> Fullwave rectifier (reverse polarity protection)
From rectifier, it divides into two groups:
-- Rectifier --> L298D, for Motors
-- Rectifier --> Arduino Nano VIN (it supports upto 20V as input voltage and outputs 5V from VCC pin)
From Arduino's VCC, I powered up the following:
-- L298D's VCC
All had a common ground (ground from rectifier).