Cheater the Pinewood Derby Car
I know some won't consider this a "robot" because it lacks a brain, but it is still fun and worth mentioning.
Anyone who is familiar with Cub Scouts, Boy Scouts, or Royal Rangers has seen a pinewood derby car before. The Kits typically include a block of wood, 4 wheels and 4 metal axles or 2 pieces of dowlrod and 4 screws. Chuck most of that because you only need a couple of the wheels and the axles.
Hot Glue Gun
Pinewood Derby Car Kit (optional)
Gears (if motor is not geared)
2 Tires with grip for back wheels
2 Bumper Switches (get at least one with the small wheel on it to use on the bottom)
4 AA Batteries with a holder
The switch on the front is wired so that it is normally closed. That means current passes through it when the switch is out. When it is pushed in by the starting block on the track it kills the motors until the starting block is dropped. Otherwise it could burn the motor.
The switch on the bottom is wired normally open so current only passes through when the car is placed on the track this helps to save the batteries. Wouldn't want it running all the time or have to flip a switch manually thats boring.
I used a dremel to put a hole in the paint stick so the gears can poke through. All of the cutting was done using a dremel.
You'll notice the picture has the switch on the bottom in the middle. The video shows it pushed to one side. I had to remount it because the track has bolts running down the middle as well as a hole near the starting gate. I had to move the sensor over or it would fall in the hole and the car would stop. That would equal about 1 inch of fun.
Things I would do different:When placed at the bottom of the track pointed uphill toward the start line it ALMOST makes it back uphill to the start. Next time I may consider adding a 5th or 6th battery and adding a motor driver so once it gets to the end of the track it goes in reverse and drives back to the start.
Also I want to have 2 sets of gears so it has to shift halfway through the race. Since it starts off by going downhill I want to have it geared for less torque and more speed, when it hits the straightaway I want it to have a little more torque so it doesn't stop. It still finished in approx 3 seconds when the other cars took 6-7 seconds.
Edit: New video. Shows the car on the track and from the car's point of view.I should have put in new batteries it was running slow.