Let's Make Robots!

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

7.4V 900mAh Lipo: ~8.00

small breadboard: 3.95

Grand total: $27

Slightly over my $25 estimate, but still not too bad.


The next big thing will be writing some code so that it can draw complicated shapes!

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

Cheap Cheap Cheap !!! I Love It. 


Love it, makes me want to make one!
How is the LM2940 working for you :)
It's great!  Easy to hook up, and working perfect.
very nice,
I like going to grow as your robot
Nice and Simple......!!! Good job :)
sorry im half asleap here sorry Chris
sorry im half asleap here sorry Chris
I was wondering how you did such a neat job cutting the CD? So far all my attempts have led to a pile of small sharp pieces. Would a dremel do it with the right attachment at the right speed?

I drilled holes for the corners using an 1/8" bit, then used many passes with a "snap-off-blade" from my local hardware store to score the lines.  In some places the snap-off-blade was able to cut through, and in other places I used a razor blade to help it along.

The cuts are good enough for my taste, but they are not so neat looking in person.  I may cover the edges with tape if I ever need to make this bot look presentable for some reason.