Coilguns(Pulse Accelerators), like railguns(Linear Accelerators), use intense electromagnetic fields to propel objects at incredible velocities unreachable with modern gas driven weaponry (given enough stored energy of course). This coil gun is known as a reluctance coil gun. The coil uses its electromagnetic field to pull a ferromagnetic (magnetically affected) projectile, in this case a shaped steel round, toward its center. Ideally the current supporting the electromagnetic field will turn off when the projectile is in the center allowing the projectile to continue traveling down the barrel, out the gun, and to the target. Use a coil and a few batteries to understand the properties of this system better. Many coilguns incorporate multiple stages at lower energy levels as efficiency tends to die off as more Stored Energy is used for a single coil design. For more information go to step 5.
A basic coilgun operation diagram is included at the bottom.
'!!!!!!Learn More About Coilguns!!!!!!'
What is a relay?? (Elaboration on step 2)
How does it work?
A relay is a simple electromagnetic switch. It uses an electromagnet to pull two contacts of a separate circuit together, completing the circuit and allowing electricity to flow.
What is it used for?
A relay was originally used to allow a machine or computer to switch something on or off electronically. In this application it is used to switch the capacitors energy into the coil.
Why use it?
Relays allow more current to pass through them than regular push button switches, which normally weld together. You can use a very high rated toggle switch for this, but it is usually more expensive and larger than a relay of the same rating.
The Parts You Need Are:
From Radio Shack or Other Electronic Parts Dealer:
-20 or 22 AWG Hookup Wire (Buy both the solid and stranded)(Larger wire is better because it lowers the resistance in the system which increases the coil gun's efficiency)
-22-20 gauge Magnetic Wire (Depending on your coil preference;See step 2)(Radio Shack has a Package with 40 ft of this but I recommend buying it from a different store to save cost and to get at least 100 ft for a coil more than 7 layers thick)
-A Relay (Electronic Switch), Preferably 30 Amps or more (I got a 12VDC/30A SPST Automotive Relay from Radio Shack, but I would recommend a higher voltage and current rating)
-A Momentary Switch( I used the SPDT Switch with 3/4" Roller Lever from Radio Shack, but you can use a lower rated switch)
-An On/Off Switch(I used the DPDT Heavy-Duty Rocker Switch from Radio Shack but you can use a lower rated switch)
-Battery Packs (More than 2 2AA Holders and 1 9V Holder)(The more 2AA Battery Packs the better)( I would suggest getting a few 2 C Battery Holders as they provide substantially more power to the Charger, resulting in a MUCH faster charge time; be careful not to over load your chargers, see last step for safe charger to battery ratios.
From Other Places:
-Used Disposable Camera's (The More The Better as this is the gun's central component), You can get them by asking most photo places like in Walmart or CVS for used disposable camera's. Remember: it is for the batteries, not a gun...never
-Straws from Burger king or local chain(You May use another place's straws but the coil's inner diameter will differ; Of course if you choose a smaller straw a smaller projectile will go faster but not pack as big a punch, AKA momentum)Also,Smaller Straws may be used to place on the back of your projetile for stabilization, this works well.
-Large Nails (3/16 to 1/4 inch Diameter, or bring your straw to Home Depot to fit the right nail)
-A Bolt, two washers, and a nut. (The bolt needs to be the diameter of your straw and the washer needs to fit well and be as wide in diameter as possible)
-A spray paint "can gun" handle or other handle. (I got mine from Harbor Freight)
-Plexiglas, wood, or sheet metal(Optional for gun casing)
-Flux (Not necessary, but it does help)
-Super Glue/ Epoxy/ Hot Glue(Used for gun casing)
-Wire Stripper( A big help)
-Glue Gun( For outer casing)
-Screw Driver(Flat Head)( To get cameras apart and discharge capacitors)
Losing Drive To Build This? Check out The Videos
The PAR-1 video demonstrates the kinetic output of a 12 layer coil with a 470uF 400V(to 450V) capacitor, that's only 50 Joules!.
My Web Page: Future Experimental Systems
Go to see some coilgun and railgun projects of mine.
Finished a coilgun and want to share it? Post it Here: Coilgun Arsenal
Useful Electronic Goods Sites:
- Mouser Probably the best Distributor I've come across, vast selection of items, best pricing for a non-wholesale electronics site, and great navigation and organization.
- Goldmine Great prices on useful parts
- Digikey Good for hard to find parts.
- MPJA Great place to buy magnetic wire and LEDs
- Electrostore Large high voltage capacitors at cheap price and other high power components.
- Surplus of Nebraska Great prices on magnetic wire if bought in large quantities.
- Alltronics An OK surplus store
Step 1: Charger Circuits
Why connect chargers into a bank?
chargers themselves aren't very powerful, but when you connect them together in parallel like shown in the last picture you increase the possible power output that the chargers can handle. Increasing the number and size of your battery bank (at 3V) will increase the chargers output (to a point) until the chargers fry.
Connecting the chargers in Parallel OR Series?
The chargers are connected in parallel, i.e. each terminal is connected to the same terminal on the adjacent charger as shown in the picture diagram. I do not recommend putting the chargers in series, so don't worry about it.
Look and read the picture comments, the pictures show you how to make your chargers better than I can describe it.
First take your circuit and use a pair of wire clippers and cut off the section defined by the small transformer on the top right of the circuit (this includes a transistor and diode)(look at the picture for reference). Attach leads as defined in the picture.
Camera circuits are mostly inefficient i.e. 16% by my testing, if you want your gun to charge faster and with less battery drain check out my DC to DC HV Boost Converter.
The Mini Charger Idea credit Comes from Instructable member "245Tommy" who got it from you tube member "Halo2maniaccc". Thank You both
TEST EACH CHARGER INDIVIDUALLY BEFORE YOU PUT THEM INTO A BANK, some may be defective.
Remember: Flux/Rosin (Which is used to enhance solder's "stick") is important here. You do not need it, but it does help a lot.