ORIGINAL: JimDrew
You could make very simple electronics for this (I did). PIC10F with a Zetex current sensor (S0-23), two dual FETs (S0-363), cap and resistor (0603). No need for A/D, yet you can measure current using this setup. You will need a voltage regulator for PIC. You could build this entire thing for dual retracts in a space of .25'' x .25'' if you needed to. In my case, I mounted the board directly to the motor's power wire tabs. This eliminates wires going to the motor. The PWM input is handled by the PIC so you just have a board with a servo plug. You use Y-cables to connect all the gear together to a single channel.
Jim,
Check out the MC33887 H-Bridge DC motor driver.... simple and perfect for this app.
http://www.freescale.com/webapp/sps/...C33887&fsrch=1
Includes a current sense feedback pin (voltage proportional to current)... no extra current sensor needed, and interfaces to a micro very easily. I also doubt very much you can place two 3A FETS (stall current of gear motors ~ 1.2-1.6 amps) and accompanying components (PIC, current sensor, reg, etc...) in a 1/4x1/4" space. Then again, space is not a problem here as I plan to have the controller inboard (fuselage), simply to keep it safe and dry! I also plan to have my controller board control many actuators, along with maybe programmable sequencing (i.e. stagger/delays), retracts speed adjustment (via PWM) and other features I (or others) drum up.