Homing a motor with a photoresistor

I did some experimenting today with a photoresistor. A few days ago, I saw a project where someone used a photoresistor as a sensor when someone walked into a room or something like that, by pointing an LED at it and then waiting until the light was interrupted by someone in the way. I thought I could use that same concept with a servo motor.

The original plan was to build something like the Frog Hopper tower I built a while back. It would actually have “eyes” this time, as I would have mounted four sensors and four LEDs up the tower to track where the car is. After a couple of hours of not getting cardboard to cooperate with me, I gave up and quickly came up with a new plan to still play around with the concept.

If you know me, you know I’m a huge amusement park fan. Half of my fun at amusement parks are just watching the rides and picking out parts of them to figure out how it all works. IMG_20130604_114029If you know me really well, you’d know that my favorite ride is Sledge Hammer at Canada’s Wonderland. A lot of people knock it because it’s not very thrilling, but I’ve been so fascinated by it since it opened in 2003. In this picture, I’ve drawn a yellow circle pointing out a green proximity sensor, lined up with a thin piece of metal attached to the gondola, or the seats of the ride. As the ride cycle is ending, the gondolas slowly spin around trying to line up the piece of metal with the proximity sensor. I find it very interesting to watch, because most of the time it will pass by it and slowly reverse back to line up with it.
IMG_1057Anyways, this is what I set up. The button on the breadboard is used to tell the system to home the motor if the motor is running, or to restart the motor if the motor is stopped.IMG_1058 The continuous rotation servo motor has a piece of cardboard attached to it. The photoresistor sits on the servo motor and has the red LED shining on it whenever the cardboard rotates out of the way. Check out the video to see how it works:

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