My new son in law will be traveling a great distance and spending his first Christmas with us. To celebrate, I thought I would make one of his packages a little different. A scrolling message tag will say, "Merry Christmas, Forrest." A solar powered mini car will race around in circles on top of the package (it is powered by a light above the package). If you get too close to the package to examine things, a voice will say, "Step away from the package!"
Drill a 1/16 inch hole for a paperclip. The paperclip will go through the wood base and the upright portion of the clip will become the "pole" in the center of the circle around which the mini-car operates.
Be certain that the car's front wheels are turned for the tightest possible circle. Place a light (I used a 100 watt halogen flood) above the board. Test the rig to be certain that the car will run continuously. The height of the light (also power and beam spread) as well as the tether length and material will affect operation. At this point, I began to wonder why I didn't obtain an N gauge train with the tightest possible circle and power it with a load of rechargeable batteries. I guess cost, availability and power drain led me to continue working with the solar car.
Obtain a Parallax motion sensor (from Radio Shack or Parallax.com). Connect a red wire wrap wire to the positive terminal (tie a small knot in the other end so that you will know it is the positive wire). Wrap a blue wire around the negative terminal. Wrap another red wire (no knot on the other end) to the output terminal. This is (2) on the schematic.
First, attach a 9 volt battery to the recording module and record your message "Step away from the package!" Speak loudly and very close to the microphone--you want all the volume you can get. When you are content with your message, cut the speaker wires about halfway between the speaker and the module.
Radio Shack's record module (#276-1323) has changed over time. You can remove the "play" switch and find a spot to solder two wires such that touching the wires connects the same spot that the switch connected. The newer modules with more SMT circuitry may require you to actually solder wire wrap wires to the traces under the play button. (5) on the schematic
Step 29: Connect and Solder the Speaker Wires to the Module
Turn the board right side up. Place the scrolling sign on its mounting bracket. Tether the car to the paperclip "pole." Turn on the motion detector. Be certain that everything runs when the light is on. The car should not run into things or leave the board--it really must run in a rather tight circle.
You can set this assembly on top of the wrapped package. If you are so sure of yourself that you've made no errors and that the batteries will last a long time, tape it to the main package. You'll need to adjust the position of your light (I used a 100 watt halogen flood) and the car's tether to get a good running combination. You may want to shield (tape and wrapping paper work well) part of the motion sensor, or it will be shouting "Stay away . . ." every time anyone gets within 20 feet of the package. Have fun!