I designed this device to allow me to control a motor with an RC receiver/transmitter setup, but the same system can be used with an Arduino! It has full motion control, going both forward and backward, and speed can be controlled. For the RC minded, this is just a cheap, DIY Electronic Speed Controller, much like those in Rc airplanes and Helis!
NOTE: When using with Arduino:
Program this with the servo library as you would program a continuous rotation servo.
This can be used with Arduino as long as a seperate battery is wired, it may draw too much power from the Arduino if ran directly off the Arduino's 5 volt pin!
Step 1: Parts and Tools
Servo (I used a Parallax servo avaliable from Radio Shack
Dc motor (mine is in a gearbox)
Soldering iron and solder
Desoldering pump or braid
Needle nose pliers
Step 2: Open the Servo
Remove the top with the servo arms. Then, take the gears and fittings out. Next, unscrew the servo arms so you are left with the top part of the casing that has a hole in it where the servo axle came out. When the screws came out, the bottom of the casing should have fallen off along with it. If not, just pop it off. You should be able to see the pcb that controls the motor. Use the small screwdriver to unscrew the motor from the top of the servo there should be two small screws. Then use the screwdriver to pry out the pcb and the motor, which is directly mounted to it. BE EXTREMELY CAREFUL NOT TO SNAP THE CIRCUIT BOARD! I did, then tried to solder it back. I made magic blue smoke! :(
Step 3: Where We Are So Far
Step 4: The Soldering
Step 5: Finishing
Also, I'm entering this in the Macgyver contest, so if you like this project, a vote would be much appreciated!