Building a Basic Robot
Well, I’ve decided that I wanted to build a basic robot based on a toy car I recently dissected. I took out all of the cheap RF stuff in there, and left the back DC motor and gear box that gives it two-wheel drive. I also modified the front wheels so that they had complete left and right freedom of motion (the radio controlled toy car had this interesting steering mechanism that had only let the wheels point straight or to the right).
What do I have left? A simplified car frame with two-wheel drive, 4 AA battery compartment housing, an on-off switch, and front wheels that can’t steer. The only thing to do mechanically is to add steering to the two front wheels, which I’ll probably do using Ackermann Steering, kind of like what cars use. I originally thought of using a gear rack, and doing a simple rack and pinion model with a stepper motor, but later I found out that the easiest (and cleanest) way is to use a servo motor. Since the two front wheels have a connecting bar that keeps the wheels parallel, I only need to focus on moving this bar left or right. A stiff wire connected from the horn of a servo motor to this bar (or a wheel) would do exactly this. Besides, servos remember their position, so all I’ll have to do is send it the angle I want the wheels to be at. I ordered two cheap 5g servo motors from ebay.
In the middle of the car, I have plenty of space to mount 1-2 breadboards. I’m going to be using a microcontroller (AVR ATTiny2313) to control the steering servo, two-wheel drive motor, a digital temperature sensor and an RF transmitter and receiver. The idea is to have a remote digital steering from a laptop, and have the robot send back temperature data when I want it to. The goal is to find the hottest part of my backyard. I’ll expand the bot after I get this basic setup working.
I already have the digital temperature sensor (DS1624, actually I sampled it), servo, and I recently ordered the RF transmitter and receiver units (these ones). All that is left is the stiff wire for the steering, and an H-bridge (L298 probably?) to control the two-wheel drive DC motor.
Here is a fairly hi-res picture of the toy radio-controlled car stripped apart: http://www.frozeneskimo.com/irvingraw.png
