"HELP!! I JUST STARTED A FIRE!!" Gertboard Wiring Problem.

One of my wires that was going to my gertboard just went alight! Here is my situation that caused the problem:

I am using the ATMEGA on the Gertboard to power a motor Shield which powers four motors, this however, is not the problem. I also have a Servo attached to the ATMEGA which uses an external powersupply (like below):

Raspberry Pi --> Gertboard (ATMEGA) --> Digital 9 --> Servo Digital Pin / +6v battery --> Servo --> GND (6v battery) + 10k Resistor (GND to battery doesn't accually go through resistor) --> GND on Gertboard

So, there is the data circuit and a power curciut.

Now heres the thing...

The bit of wire that went on fire (Servo --> Resistor --> FIRE!!! --> GertBoard GND) occured when I have the Resistor doubled over so that it could fit in the Servo motor hole withou falling out (Could be problem one). The other problem could just be the whole way I am wiring.

I will make up a schematic to show you exactly what I have but does anyone have any advice on wiring up the ATMEGA and Servo (with Servo external Power-supply)?

GreenYamo over 12 years ago

Hello Cian,

I'm far from being an expert on this and I don't know much about the gertboard either and what it supplies in terms of protection, but driving a motor normally needs some kind of buffer to avoid too high a current draw from the Pi (eg, using a transistor as a switch), and also protection to stop back EMF from the motor (diode).
You'll need a common ground as well between the external power supply and pi.
If you put up a schematic, i'm sure someone that **actually* knows what they are talking about will be along to explain.
Steve
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
wallarug over 12 years ago in reply to GreenYamo

Here is a Schematic (or simillar):

Extra picture is exactly how I had the Resistor in the servo pin hole.

Just some notes:
Servo pin is on the left:
- orange / yellow = data
- red is power +6volts
- Black is Ground

Blue thing is the resistor.

Brown thing on top left is a battery.
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
mconners over 12 years ago in reply to wallarug

You had to have something touching. That shouldn't have been a problem the way it is diagrammed, although I question the utility of the resistor. Doube check all of your connections.

Mike
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
wallarug over 12 years ago in reply to mconners

Does the location of the fire assist in anyway to discover the location of the fault?

Also, thanks for the reply. I am glad that you say that it correct.
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
wallarug over 12 years ago in reply to wallarug

Just found this: http://learn.adafruit.com/adafruits-raspberry-pi-lesson-8-using-a-servo-motor/hardware

Maybe this could help me solve this problem.
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel
mconners over 12 years ago in reply to wallarug

That pretty much looks like what you had. Grounds connected, isolated power, GPIO pin 18 seems to be one of the keys. Lady Ada knows what she is doing so that may be your answer.

Good luck,

Mike
Cancel
Vote Up 0 Vote Down

Sign in to reply

Cancel