The Scrap RC Robot
In my junk pile was a couple of relays, servos and a radio, but I needed a robot!
Every pseudo-nerd accumulates flashlights, I don't know why. I bought a Garrity generator flashlight http://www.garritylites.com/page116.html from Harris Teeter (I have never owned a generator flashlight that was truly useful) but, of course, I had one. I decided to take it apart. Inside was a GREAT reduction gear system for an excellent robot transmission. The generator (now motor) didn't seem to mind 7.2 volts either! I went back to Harris Teeter and purchased another one, I think they were like 10 bucks a piece. The gear train is nice but you get all kinds of other goodies packed in these flashlights; AC to DC converters (to charge by winding in both directions), 3.6 volt 300mah NMH batteries, LEDs, switches, diodes, etc.
Power
To power the beast I needed at least 6 volts for the relays (9 volt relays), and 5 volts for the radio and servos so a cheap NiCad 7.2 volt 1800Mah RC battery suited my purposes just fine.
Servos/Radio
I wanted simple, I didn't have any solid state speed controllers but I was hoping to have a mechanical speed controller laying around, I didn't. So I decided to make one. I drilled and glued a perforated circuit board to each servo. I then wove copper wire through the holes as contacts. On the servo horn, I put solderwick (braided copper) as a contact and zip tied it on. There are a thousand ways to make this robot, I opted to use relays instead of direct control with the servos because I might add to this thing later. The idea is Straight (both motors on), Left (left motor off, right motor on), Right (left motor on, right motor off), and this will be for Forward and Reverse. One servo for Forward/Reverse, and one servo for Left/Right.
Relay system
The Steering Relays are normally closed, when the servo powers one of these relays (left or right), that relay will open and cut power to the corresponding motor. The other servo controls forward and reverse. The Forward/Reverse relay simply reverses current to the steering relays.
Drive train
I just mounted the transmissions to an empty .45 box with zip ties, and made holes in the plastic with a soldering iron. The only stupid thing I did here was forgot to take into account that I was reversing the direction of the motor by flipping it, so make sure you switch the polarity of one of the motors so they both end up turning in opposite directions (one forward direction for the car).
Wheels
I skimped on the wheels, I used the arm coupler for the crank of the generators and double stick taped them to an empty shoe polish can!
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