A magnetic coil gun sounds like something from science fiction, but you can build one at home using parts from a disposable camera. It works on the same principle as the loudspeaker, through an effect called induction, current passing through a coiled wire creates a magnetic field. In your stereo, that magnetic field moves the speaker cone back and forth. In the coil gun, it fires a metal projectile across the room.
- Skill level:
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Things you need
- Disposable camera
- Philips screwdriver
- Plastic pen
- Bare copper wire
- Insulated copper wire
- Electrical tape
- Soldering iron
- Battery case for D-cell battery
- D-cell battery
- BBs or small ball bearings
- 2 single pole, single throw switches
Remove the paper wrapper from the camera and open the camera case using the screwdriver. Remove the film and battery from the camera. You should now be able to see the circuit board. Do not touch it.
Find the capacitor on the camera circuit board. It will be a large cylindrical component. Holding the screwdriver by the handle, use the metal end to bridge the two leads of the capacitor. This discharges the capacitor, making it safe to handle.
Remove the circuit board from the camera.
Solder the + and - terminals of the battery case to the pads on the circuit board that led to battery terminals in the camera. Use the insulated wire for this, and make sure to match the polarity correctly.
Find the pads on the circuit board that led to the button that charges the flash. Using insulated wire, solder a switch across these pads. When you throw this switch, the capacitor will charge from the battery.
Disassemble the pen. The plastic tube will be the barrel of the gun.
Coil uninsulated wire around the closed end of the tube. Wind the coils tightly and close together, but make sure they do not overlap. The coil should be about an inch and a half wide, and end about half an inch from the end of the tube. Leave a wire lead before the coil, so you can connect it to the circuit.
When you have finished a layer of coil, wrap it in tape to insulate it and continue coiling the wire to make another layer. Wind each layer the same way, either clockwise or counterclockwise. Make a few layers, and be sure to insulate them from each other.
Using insulated wire, solder one of the leads from the coil to a terminal of a switch, and solder the other terminal of the switch to one of the capacitor leads on the circuit board. Solder the other lead from the coil to the other capacitor lead. When you throw this switch, the gun will fire.
Make sure both switches are open (disconnected), then load the battery into the clip. Throw the switch connected to the flash terminals to charge the capacitor. Wait a minute or so, and then turn the switch off. Load the gun with a ball bearing or BB. Any metal object that will fit in the tube and reacts to magnetism will work.
Point the gun at the target, and flip the switch connected to the capacitor to fire the gun.
Tips and warnings
- To make a more powerful coil gun, remove the capacitors from a number of disposable cameras and connect them in parallel. In this configuration they function as a single large capacitor. Be careful, as a coil gun built this way will carry a very strong current.
- Make sure the firing switch is off before you charge the capacitor.
- When you're finished using your coil gun, remove the battery and discharge the capacitor by firing the gun without the battery in, or by running a screwdriver across the capacitor leads.
- Your coil gun is dangerous. Never point it at anything living.