Arduino Motor Shield V3 acting weird


SO I have the code below. Both wheels are supposed to turn forward. They start out turning forward, then one of the motor seems to 'suck up' the energy and turn forward at a faster speed. The other motor slows down and stops running. If I hold the running motor down, and force it 'back', then the other motor starts running.

What gives? I thought it might be an power issue, so I hooked up an additional 9.6 Lithium ion battery directly to the motor board. No change, except the motors run faster.

Also, the motors simply don't spin if I set pin 12 and 13 to 1. So turning left/right is impossible.

I purchased the components from radio shack. (Like, from a store front
-Arduino Uno Rev 3
-Arduino Motor Shield Rev 3
-2x Metal Gear 1.5-3V DC Motor

void setup()

void loop()

You forgot pinMode(pin, OUTPUT) on all your output pins.

OKay, I went ahead and did that. The result is that they activate more reliably, but the results are still spotty. Every 1 out of 3 tries I still have to 'spin' the wheel to get it going.

When you say "Arduino Motor Shield Rev 3" do you mean this one?

If not, what board do you mean.

If it is the one you are using you might want to do something with those Brake pins.

Function pins per Ch. A pins per Ch. B
Direction D12 D13
PWM D3 D11
Brake D9 D8
Current Sensing A0 A1

Yep, that's the one. I guess I'll try setting the pinMode(number,OUTPUT); for each break pin, see if that works. And I guess I'll set pinMode(number,INPUT) for the two current sensors.

It's odd, I didn't have these kinds of problems with the Adafruit motorshield at all, but they do supply a handy library for it. Do you know if there is an Arduino Motor Shield library available??

Are there any other threads/guides to using this particular motor shield? when I do a search most people refer to AF or other brands of motor shields.

Probably the best thing to do is study the datasheet of the chip on which the motor shield is based.

Hi, TarISS
Now i'm facing almost the same problem, it's so weird. Did you get the solution of this? Thanks for help.