Baby-O Post Mortem - Please Help

Hello All,

I was making a reference design of the robot at openmelt.org with my own custom circuit board which is controlled by a Baby Orangutan. I plugged everything in today and found that my high power status LEDs which are driven by M1 were not lighting. After consulting the reference design I noticed I had soldered them in backwards. After consulting this page https://www.pololu.com/docs/0J27/8 , I decided to change all the mentions of pin 5 to pin 6 in the following code:

//definitions for LED pin #define set_led_on() PORTD |= _BV(PD6) //portd.6 - heading indicator LED control PIN (powers LED connected to motor controller on M1a / M1b) #define set_led_off() PORTD &= ~_BV(PD6) #define toggle_led() PORTD ^= 1<<PIND6 #define set_led_pin_as_output() DDRD |= 1<<DDD6
That seemed to fix the problem, although perhaps it was a bad idea considering what happened next. (I dont know if this is just a coincidence)

After 20 minutes of off and on testing I smelled magic smoke and unplugged the power. The LEDs no longer light and that part of the Baby-O under the half bridge gets hot. I was using a 3S LiPo battery back that was at 12.2 V with 6.05 forward voltage worth of LEDs and a 25 ohm resistor. (12.2-6.05)/25=246mA which should be fine.

I am sure the h-bridge is dead. It heats up even with nothing closing the circuit between M1A and M1B. I am still trying to figure out why. The board was stationary on a desk when it died. I tested the LEDs on a separate supply, they still work. There is no short between m1a and m1b, I read a resistance of 69k between them. There is a short between M2A and M2B (resistance .8 Ohms). I dont know how to interpret that because M2 was not in use, it was not even soldered to my custom board. Perhaps the short developed as the h-bridge died, or perhaps M2A-M2B has a low resistance if the semiconductor magic inside defaults to a low resistance brake state?

Any advice on figuring out what killed it? I am getting crunched for time and I dont relish the idea of buying a new Baby-O only to plug it into a death trap.

Hello.

I am sorry you are having problems with your Baby Orangutan. It sounds like the motor driver is damaged. Could you post pictures of your setup? Could you also post your entire program? It looks like the resistor in series with the LEDs had to dissipate a lot of power (about 1.5W). Did you use a power resistor? If so, what was it rated at? By the way, the page you referenced is for the Orangutan LV and Orangutan SV. You should be referring to the Baby Orangutan User’s Guide instead.

It sounds like you are in a hurry. If you contact us directly at support@pololu.com and reference this forum post, I might be able to help you with a discount on a replacement.

- Jeremy