My daughter choose to see if a robot could make a art for her science fair project.
Now there are jittering soda cans with a marker attached to them and when you put in a piece of paper under it, it wil make art. To me thats random chance and while its a vaild way of solving the problem is seems a bit low tech. I happen to have a spare HP inkjet (8610 iirc) which has all kinds of gears, motors... roboty things. Most important is the Linear Motion Slide Actuator.
At first we were going to make the actuator swing left to right much like windshield wiper. Due to the weight of the actuator I did not have a motor strong enough to move it. So we decided to make it stationary much like the printer did and move the paper under it. We came up with attaching a metal coffee can to a toy DC motor and spin the can under the actuator. We tested this out and it worked quite well!
I have a few raspberry pi laying around. The one I choose was a very older model B. Something I wouldn't mind getting broken. I found a easy enough circuit to make at robotroom and ordered the necessary chips from Mouser Electronics, but they wouldn't arrive in time to build and complete the experiment. After combing google for an alternative circuit I came across this handy DC Motor Reversing Circuit made using simple switches and relays. I ordered a few small bread boards to work with, a 4 port programmable relay and some limit or action switches.
I had a few small power step down modules and also a 10v 1A wall wart power supply. One step down module for the pi, and one for the two motors. She can change dial the power up and down on the second one to get different designs.
Building the circuit was pretty easy as well as connecting it the pi. Programing the robot to read the switches and reverse the relays which just reversed the polarity of the motor was a bit harder. For a moment that thing seemed to be self aware with all the self imposed bugs.
Since this bot would be running headless we added a LED to the circuit to let her know when the robot was ready. Then we added a push button to make the robot start and stop.
In the end she was happy with the robot.
Here is the front of the robot.
This is the backside
An up close of the components
The final project
Here it is in action!