I'm building an ROV, and I'm trying to use an arduino to control several bilge pumps for movement control. I've been having an issue with finding a motor shield that will allow me to control a 12v motor with a 9A peak draw, probably around 4-5A constant. I need to control at least 4 of these motors; any ideas? I haven't seen any on the playground that could handle that current, nor have I found any purchasable. Any help?
You probably need to look for some industrial controller stuff, or build your own from suitable power transistor and maybe a relay.
a cheap way to do it would be to use brushed RC motor controllers. you wire them up just like a servo, though some need special arming procedures.
how about this
http://www.dealextreme.com/details.dx/sku.15581 //lacking specs
or this
http://www.dealextreme.com/details.dx/sku.15759 //would work but relatively expensive to buy several.
anyway, you can see where im going with this. there are options out there.
Actually this would be a easy application of a logic level power MOSFET transistor either for PWM or on/off control. Be sure it's a logic level MOSFET so that the Arduino +5vdc output can fully turn it on.
Just find one rated at double or triple the surge current ratings and wire a reversed biased diode across the motor winding terminals. You can wire the gate of the MOSFET striaght to a Arduino output pin, drain to ground and source to motor terminal and other motor lead to +12vdc. Add a pull down resistor to the Arduion ouput pin to ground (1K) if there is the possiblity of the Arduino of being powered off but the +12vdc still powered on.
Here is one popular example device:
Lefty