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10-14-2008

A Basic Coil Gun (Coil Pistol, Coil Rifle)

A small coil gun that can demonstrate the principal of operation of these devices can be constructed from commonly available materials in about an hour. The energy used in this coil gun is less than lethal so it can be considered reasonably safe. However you should exercise caution as the energy stored in the capacitors used can cause considerable pain, minor electrical burns, and temporary muscular paralysis.

What you need.

Tools:

  • Soldering iorn.
  • Solder.
  • Wire cutters.
  • Hot air gun.
  • Hot glue gun.
  • Flathead screw driver.

Parts:

  • Used Disposable Camera. (Preferably of Fugifilm Type)
  • Small S.C.R or large transistor. (TO3)
  • Hookup wire.
  • 30 cm Heatshrink pipe. (For insulating high voltage connections)
  • Momentery Push-To-Make Switch.
  • 2 AA battery Holder
  • Single pole single throw toggle switch.
  • Cotton bud and a small spool of 0.3 mm wire.
  • Red and black nailpolish
  • Areldyte 5 minute crystal epoxy resin or similar adheasive
  • A bag of small nails, these should be about 10 mm long and about 1 mm wide

All the required materials to construct the basic coil gun are available from general electronics stores such as Dick Smith Electronics and Jaycar. If you live in New Zealand All parts can be sourced from Surplustronics The Required disposable camera can be obtained from most photo shops that process film.

It may take a while to find a store that will give you a camera as many of them send the used cameras back to the factory for recycling. Some photo shops will give you the cameras if you are nice. You will probably have to look around a bit.

Construction:

First you will need to extract the charger circuit and capacitor from the disposable camera. do this by carefully prise the front off the camera by breaking the tabs on the side of the camera with the screw driver. you may wish to wear gloves at this point to help avoid being shocked by the capacitor as the capacitors in these cameras can remain charged for a long time. After you have prised off the front of the camera, it should look something like this:

 After you have prised off the front of the camera

The green PCB with the flash and capacitor connected to it is the charging circuit. Pull this circuit off the front of the camera and discard the rest of the camera. Short the leads of the capacitor with the screwdriver. this may make a bang if the capacitor is charged.

This is what the circuit should look like when you remove it from the camera:

This is what the circuit should look like when you remove it from the camera

You now need to desolder the capacitor and the battery connectors, as well as the trigger switch and the flash bulb. I would recommend that you now use the red and black nail polish to label the positive and negative sides of the capacitor connections and the positive and negative side of the battery connection. This will make attachment of the connection wires much easier.

You now need to solder connection leads on to the connections that you removed the capacitor and the battery holder from. You should have already labelled these connections so you just need to solder some wires on.

Locate the two solder pads on the camerea that the charge switch touches and solder them together.

You should now have something that looks like this:

НYou should now have something that looks like this

You now need to wind the coil.

The coil will be wound on the cotton bud, cut the end off both ends of the cotton bud so you are left with a small plastic pipe about 40 mm long. This is what you will use as a coil form.

To make the coil, you need to wind around 4 layers of the 0.3 mm wire around the cotton bud. Because the projectile is about 10 mm long, you should start winding the coil about 10 mm from one end. Securing the wire to the coil form with duct tape will make winding the coil much easier. I also recommend covering each layer with a thin coat of epoxy resin to hold the layer in place and insulate it better. Also place a drop of epoxy in the short end of the barrel where the projectile will sit, this coil gun is a muzzleloader.

A Basic Coil Gun

Once you have made the coil, you are ready to solder the remaining components together. Use the circuit diagram bellow:

once you have soldered the components in place as per the diagram, your mini coil gun should shoot. I recommend placing the components inside a project box to avoid electrocution hazards and to make it easier to use.

To fire your mini coil gun, first make a projectile. To do this, take a finishing nail and using your wire cutters, cut the head off. Place the rest of the nail in the barrel of the coil gun and tip the barrel so that the projectile slides back behind the coil, coming to rest against the epoxy plug. Now put the batteries in the battery holder and turn on the charging switch. if all is done correctly, you will hear a high pitched wine as the camera circuit charges the capacitors. When the neon light on the camera circuit begins to blink, the mini coil gun is charged and ready to fire. To fire the mini coil gun, point it towards your target and press the fire switch. The mini coil gun should send the projectile toward the target at a reasonable speed.

The Mk I coil Pistol

This pistol has a muzzle energy or arround 2 joules and a rechrge time of about 10 seconds. The gun is of a single shot bolt action design as I do not posess the machining skills needed to produce a semi-automatic clip mechanisim. The power source is two 1.5 v batteries mounted on the back of the gun for ease of use and portability. I get arround ten shots from a fresh set of batteries.

The Mk I coil Pistol

The Mk II Coil Rifle

This is my second coil rifle, it has a firing energy of about 5 joules and it charges in about 10 seconds. the power source is the 12 V 3.5 AH SLA batery. This supplies the power to the 12 v - 240 v inverter that provides the 240 v requiered by the rectifacation circut. The 400 v output from this circut is used to charge the two 400 v 2200 uF capacitors used to supply the energy to the work coil. it is capable of shooting through multiple soda cans.

The Mk II Coil RIfle

geocities.com/njh_howard/

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