CD Turtle

CD Turtle
CD Turtle

Goal: Make a robot that draws and takes some of the same commands as KTurtle. Eventually this robot will draw using a marker through the hole of the CD.

I like to try to find the cheapest possible way to make things. Here's the list of materials so far:

Item: Price

2 HXT900 Servos: $3.65each= $7.30

discarded CD: $0.00

discarded RC airplane wheels: $0.00

Grand total: $7.30

Planned additions:

ATmega8: ~4.00

754410 quad half-H: ~1.50

5V 1A linear regulator: ~0.47

7.4V 900mAh Lipo: ~8.00 (be VERY careful with lipos. They can burst into flame if abused. Many hobbyists have had fires from handling lipos improperly.)

I think the total cost of this project can be kept under $25 with some careful scrounging.

UPDATE----- 8/12/2008

I hooked up the electronics without mounting them in the bot, just to check things out. I'm glad I did, since I found that my voltage regulator (LM2931, just because I had it handy) heated up quite a bit and the voltage dropped to three volts when the motors are both running! Other than that things seem to be working okay.

As soon as some of the LM2940 regulators come in from Digikey I'll be up and running! Thanks for the suggestion in your comment, Krumlink.

UPDATE----- 8/15/2008

Woohoo! It drives, it draws, it needs more work!

At first I tried to use the LM2940 for both the motors and the AVR, but it had some weird problems, even with a 100uF cap between VCC and GND on the AVR. I kept the LM2940 for the motors, and used a LM2931 for the AVR. Much better now!

It drives around and draws, but it needs some work. The pen is a snug fit in the tube, so it can't slide up and down easily. Since the wheels are slightly out of round, the pen draws only when the robot is in the lower part of each revolution of the wheels. I'll fix it by making a larger tube so the pen's weight can keep it in contact with the paper.

Here's the list of components so far:

2 HXT900 Servos: $3.65each= $7.30

discarded CD: $0.00

discarded RC airplane wheels: $0.00

ATmega8: ~4.00

754410 quad half-H: ~1.50

LM2940: ~1.50

LM2931: ~.75

2x 100uF cap

2x 1/4w resistors

5 pin connector for programmer

part of a ball point pen to slide on