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!"
Step 1: Drill Hole in Solar Mini Car
You will need a solar powered mini-car (thinkgeek.com). Carefully drill a 1/16 inch hole in the side.
Step 2: Cut Thin Plywood to Match Top of Your Package.
I cut a 12 inch by 12 inch piece of 1/4 inch plywood to match the top of the package I'm wrapping.
Step 3: Cut Standoffs for the Base.
I cut four 1 1/2 inch by 1 1/2 inch blocks of wood. I cut them 1/12 inches long (cubes).
Step 4: Cut Pvc Pipe for Sound Amplification
Cut a 3 inch long piece of PVC pipe (1 7/8 inch outside diameter). This will be used to hold the motion sensor and the speaker (makes the sound much louder).
Step 5: Find Spot for PVC Placement
Select a place to mount the PVC tube. It must leave room for the mini-car to operate.
Step 6: Drill Hole for Pipe.
Drill a 1 7/8 inch diameter hole for the PVC pipe.
Step 7: Drill Hole in the Pipe for Motion Detector
Drill a 7/8 inch hole in the PVC pipe (near an end) for the motion sensor.
Step 8: Glue Standoff Blocks to Plywood
Glue the blocks in the corners of the plywood.
Step 9: Add Battery Holder
Fasten (with two small wood screws) the battery holder (3 AAA unit) to one of the corners.
Step 10: Mount On/off Switch
Drill a hole and mount the on/off toggle switch.
Step 11: Drill Hole Behind PVC Tube Hole
Drill a 1/4 inch hole behind the PVC tube hole. This will be used to run wires, so make sure it is on the side that will be least obvious when the package is displayed.
Step 12: Drill Hole for Paper Clip
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.
Step 13: Glue Paperclip in Place
This is the bottom of the base. Epoxy the paperclip in place; otherwise, it will probably fall out.
Step 14: Tether the Mini-car
Fasten a tether to the mini-car. My tether is about 3 inches long and it is made of #32 magnet wire.
Step 15: Test the Car
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.
Step 16: Wiring Step #1
Attach the positive wire (red) from the battery holder to the switch (1 on the schematic).
Step 17: Attach Wires to the Motion Sensor
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.
Step 18: Insert Motion Sensor in PVC Tube
Step 19: Secure Motion Sensor
I stuffed paper towel bits behind the motion sensor until it was held in place (this is just Christmas wrapping).
Step 20: Cut the Speaker Wires Loose From the Recording Module
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.
Step 21: Add Wires to the Speaker
Add about 8 inches of wire to the speaker wires.
Step 22: Add Electrical Tape Around the Speaker
Cut thin strips of electrical tape and wrap that around the speaker. This will be used to "force fit" the speaker into the PVC tube.
Step 23: Push the Speaker Into the PVC Tube
Push the speaker into the PVC tube (same end of tube as the motion detector). It should be a snug fit.
Step 24: Place the PVC Tube Into the Plywood
You should be able to get a snug friction fit of the PVC into the hole in the plywood. If the PVC is too loose, wrap electrical tape around the pipe until you can obtain a snug fit.
Step 25: Take the Speaker Wires and Place Them Through the Plywood
Step 26: Add the Positive Wire From the Motion Sensor to the Switch
Note the little loop in the wire wrap wire. If I failed to identify that wire earlier, I wouldn't know which wire goes to the switch. (3) on the schematic.
Step 27: Connect Negative From Motion Sensor to Battery Negative
(4) on schematic
Step 28: Attach Wires to Play Button on Record 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
(6) on the schematic
Step 30: Tape the Speaker Wire Connection
Step 31: Glue a 5 Volt Dc Relay to the Bottom of the Plywood
Step 32: Attach the "play" Button Wires From the Module to the Relay (N.O. Contact)
(7) on the schematic
Step 33: Connect the Motion Sensor Output
This is the output from the motion sensor, through a 270 ohm resistor to the base of a NPN transistor.
(8) on the schematic
Step 34: Connect Battery Negative to the Transistor
(9) on the schematic
Step 35: To the Transistor, Attach a Diode and a Wire (headed Toward Relay)
(10) on schematic
Step 36: Attach Wire From Transistor to Relay
(11) on schematic
Step 37: Attach Wire to Other Side of Relay Coil
(12) on schematic
Step 38: Attach Wire From Coil to Diode
(13) on schematic
Step 39: Attach Wire to Coil, Headed Toward Battery Positive
(14) on schematic
Step 40: Attach Wire From Relay to Positive on Switch
(15) on schematic
Step 41: Cut a Stainless Strip
Take a 1/2 inch by 6 inch stainless steel strip and trim the end so that it will fit between the magnets on the scrolling message sign's (thinkgeek.com) magnetic holder.
Step 42: Fasten Scrolling Sign Mount
Drill a hole and fasten the "billboard support" to the plywood.
Step 43: Add Batteries
Add a 9 volt battery to the speech module and add 3 AAA's to the motion sensor supply. Using electrical tape, tape down anything that is loose or that looks like it will touch something electrical.
Step 44: Test
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.
Step 45: Add Wrapping Paper
This takes a while, as you have to work around the switch, paperclip "pole", PVC pipe, wires and sign mount.
It is very critical to keep a smooth running surface for the car.
Step 46: Adjust
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.