In this tutorial I hope to show you how to make an easy and affordable coil gun in depth, step by step! I'm not an expert in this field so if I can do it you can do it too! Most likely better!! :)
Step 1: How It Works... Generally
A coil gun works by turning a coil into an electromagnet and accelerating a piece of ferromagnet material (a projectile) down a tube at a high velocity.
Whoa hold up.
Let's start from the beginning: When you run electricity through a wire you naturally get a magnetic field that circles that wire, kind of like the picture above with the green circling magnetic field.
Now, imagine turning that wire a dozen times until it becomes a coil! Those magnetic fields stack in a way that create polarity, north and south, and therefore making... an electromagnet!
Okay, so... remember when we played with magnets as a kid, and the magnetic pull between two magnets was stronger the closer it got? Keep that in mind! When you turn a coil into a magnet, obviously something made of iron will be attracted to it and accelerate over and stick to the coil right? Accelerate. That's the key word! Because if you remember, the closer the magnets got to each other the stronger they pulled, and the further away they were the weaker they pulled.
Keeping this in mind, if we were to place a regular magnet on the table, then set another on the table away from it, and slowly inched one toward the stationary one, they would eventually accelerate toward each other and stick to each other. What if we magically made the stationary magnet disappear right before they touched? The accelerating magnet would continue on it's path with the momentum it gained from the magnetic field's attraction right? Now, applying this to the coil and electromagnetism, what if we turned the electromagnet on and off really fast, it would be the same thing as making the stationary magnet disappear! That is essentially how a coil accelerator works. And although we can't possibly turn something on and off fast enough to make it efficient, flash camera capacitors release a lot of energy in a short amount of time. That's perfect! It would turn the electromagnet on and off really quickly, which makes those capacitors perfect for a coil gun.
Step 2: Materials
The materials you'll be needing for this project will include the following:
- disposable cameras
- wire (I used stereo wire)
- alligator clips
- a terminal port
- a switch
- enamel coated 22-30 guage magnet wire
- wood wheels (not necessary but very helpful)
- 1/2" diameter pvc pipe (around 6" long)
- projectile (ferromagnetic is preferable [iron...])
- project box
As for the tools:
- duct tape
- electric tape
- solder and soldering iron
- various drilling and cutting equipment
- hot glue gun
- sand paper
- Time and Patience!!!
Step 3: SAFETY!!!
- NEVER touch the output wires or let anyone (including pets) come in contact with the wires. Doing so WILL result in serious injury or worse...
- ALWAYS keep the capacitor bank shorted out when not in use (that means connecting negative and positive together so no charge can be accumulated). Also remove the battery/power supply from the charger when not in use.
- Only build this if you are confident in electronics and high voltage.
- Capacitors out of disposable cameras are going to be very cheap in build quality and are not intended for long term use. So do not use this bank in a critical application.
- If one capacitor goes bad then there is a chance of it exploding with all of the energy of others being discharged into the bad one.
- Use safety goggles or a protective barrier of some sort when creating sparks.
I am in no way responsible if you mess up with this circuit. If you mess up, receive an electrical shock or burn your house down whilst making this circuit you have no-one to blame but yourself. By following this guide in order to make this circuit you agree to accepting all liability if something were to go wrong.
Step 4: Disassemble Cameras
First thing's first. You have to get disposable cameras. You can go to any Walgreens or any other store that develops disposable cameras and ask them for their disposable cameras that they were going to throw away. I just walked up and explained the project that I was doing and that there was a component in the disposable cameras that I could use and that if they had any in their trash that they were going to throw out, that it would be nice if I could take them off their hands.
After you get your disposable cameras it's time to take them apart. Remember, there is still a chance that these cameras are still charged so be careful and take your time. Mistakes can really hurt. Do what you have to do to pry open the plastic casing (I used a minus screw driver) while being careful to not touch anything metallic (it might shock you).
After removing the plastic casing, locate the battery and remove it from the camera to ensure that the camera doesn't recharge after you discharge.
As stated earlier, you have to discharge the camera. Locate the capacitor and its connections to the circuit board. You're going to want to bridge a connection between the positive and negative sides of the capacitor with something conductive (I used that minus screw driver, seemed to work best). Be careful because doing so will spark the remaining energy at the connection point. Wear eye protection and stand a little further back just in case. If there is no spark then that's good, there was no energy in the circuit then. (But to be sure, touch all of the connections on the circuit board with the screwdriver to ensure the entire circuit is dead).
From here you're going to have to observe and make some decisions. The picture included in this step is an example of a push button charging circuit. If you have ever bought a disposable camera before then you may have noticed that there are different types of switches for charging, like push button switches, lever switches, slide switches, and many more. The one you want for your permanent charging circuit is the push button circuit.
If you find a push button take your time with it and try to pry the charging circuit out of the plastic housing slowly and in one piece as carefully as you can. If not then no worries, you probably have plenty more to try from. If you find a good one and take it out of the housing neatly and intact, keep it intact (aka don't take the capacitor out of this one).
If you find anything other than a push button charger then do whatever you have to do to get that circuit out of the casing as quickly as possible (time is money), all you need is the capacitors from that circuit and nothing else.
With the one's that aren't a push charger, get your soldering iron warmed up and heat up the solder that's holding the capacitor in place. If you don't have a soldering sponge or something to suck up the excess solder just wiggle the capacitor while melting till it comes out of the circuit. Keep this capacitor for later.
Repeat this process with as many capacitors as you like, I ended up using 13 in my capacitor bank and 1 connected to the charging circuit (more on that later).
While you're at it, cut off a piece of the plastic housing+circuit board off to make a battery port. It should be the place where the battery would be, along with the metal prongs that touch the battery, but without all of the other circuit stuff and plastic. Take a look at the picture as a reference.
Step 5: Build Capacitor Bank
Great! Now you've got a bunch of batteries, capacitors, and candidates for a permanent charging circuit! Now what...
You're gonna make a capacitor bank that's what!
First thing's first, glasses!
Next, grab your breadboard and insert your capacitors in them, MAKING SURE THAT THEY ARE LINED UP IN PARALLEL!!! (positives on one side, negatives on the other). You can tell which side is negative by the band along the side of the capacitor, the opposite side is positive (of course).
After you have them all lined up, cut some pieces of wire (making sure there is ample room at the ends for connections to the rest of the circuit) and size it up next to the bank. I took stereo wire, stripped the plastic casing off, then twisted the smaller wires together to form a big wire.
What I did was split the twisted stereo wire in the middle, then stick the positive and negative charge connections through the split you made, then solder it in place. Do this along both sides, positive and negative, and this should make what seems like 2 rails. I did this process twice because I didn't want any connection problems, and I wanted the capacitor bank to be of the highest quality because it was also the most dangerous part.
Step 6: Build Coil
If someone tells you that you can make a coil out of just any wire, tell them they're absolutely wrong! The biggest difference between a working coil and a sparking coil is whether or not it is coated. Plastic and enamel coated wires will work, but if they are not coated in some way, the energy will spark across the wires, taking the path of least resistance, and run across the wires instead of through, leaving you with a spark and no magnetic force.
What I did (You are free to use your own method, this is mine to give you an idea of what worked):
I bought some wooden wheels at ACE hardware down the street, and drilled holes in the center of them, a little bigger than 1/2" so they would slide onto the PVC pipe.
First I needed a way to keep my coil in place. I took my PVC pipe and wrapped electric tape on one of the ends (to keep the wheel in place).
I then slid one of my wheels in till it was stopped by the electric tape.
I estimated around 1.5" of coil would be good so I gave myself that amount of room and then did the same thing as before but backward. (I slid the wheel in first, then wrapped the electric tape stopper where I figured the other barrier should be).
Then came the fun part (not). Wrapping! Take your time and make it as tight as possible, remember, the more turns of the coil you make the more magnetic force it will generate. Same thing goes with voltage, the more voltage you put in, the more electro-magnetic force you will generate!
Make sure you have the start and end of your wire sticking out a ways away from the coil to make connecting to the rest of the circuit easier.
I ended up not being satisfied with the power of my coil, so I soldered and attached another enamel coated magnet wire to the previous already wrapped one and kept on wrapping, making the coil out of two lengths of wire.
REMEMBER: you have to use sand paper to grind off the ends of the enamel coated wire to ensure a solid connection, otherwise the enamel will just prevent any connection from happening and that would be a stupid mistake! ... That I've made. But one that you don't have to!
Step 7: Connect the Pieces
Let's start from the capacitor bank. Take your capacitor bank's ends and put them into the terminal block, keeping in mind to keep the positives and the negatives separate.
Then, grab some wire and connect the positive and negative sides of the terminal port to the positive and negative connections on the capacitor in the charging circuit. I wrapped my stereo wire around each base of the connections for the capacitor and soldered them in place (making sure to not have the positive and negative sides touch at any point in the circuit).
Then, solder a wire connection from the battery plus and minus on the charging circuit to the battery plus and minus on the battery port.
Next, unscrew the plus and minus connections to the terminal block from the charging circuit and tie in two more wires. Therefore it will be 2 wires from the capacitor bank on one side of the block, and 2 wires from the charging circuit and 2 from the switch and coil connection on the other side of the terminal block.
Speaking of coil and switch connection, connect the coil and switch as shown in the schematic and attach it to the wires we just connected to the terminal block.
After this test it out! SAFELY!
To test it, put a battery in the battery port and click the camera flash charge button to start charging the capacitors. If all goes well there should be a light humming sound signifying that the capacitors are charging.
Make sure to keep a voltmeter touching the positive and negative ends of the capacitor bank to watch its voltage.
The capacitors will only charge up to the lowest volt capacitor, generally flash capacitors will be able to handle 330v each, but if there is a lower one then that is your max cap. Give yourself a safe 50 volts from the max amount of voltage you charge up. So if you have 330v as a max, charge until it reaches 280.
To stop charging, carefully remove the battery from the battery port. I did this with electric tape and making a sort of grabbing tail off the side of the battery and pulling on it to tug the battery out whenever I wanted to stop charging.
Keep in mind that the circuit won't charge if the switch is in the off position!
When you are ready to test fire, take all your safety precautions, insert your projectile (I used a drill bit, the larger mass you have as a projectile the more magnetic force will be produced, cylinders work better than bbs), then flip the switch!
Step 8: Assemble Into Project Box
If the test worked and it's everything you wanted then it's time to put it safely in a project box! No one likes playing around live wires... That's deadly.
I found the largest project box they had at radio shack and started drilling tiny holes and connecting the dots together to make rectangular holes. I made holes for the switch and coil connections on one side, a hole on the other side for the voltmeter probes to stick into, and a hole on top for the external battery port.
I ended up putting a clothespin permanently (with hot glue) on the charge button for the charging circuit and decided that unhooking and hooking the alligator clip up to the battery port would be a better option than pushing (touching) the charging circuit... maybe a bit safer...
I taped the charging circuit on the inside top of the box and threaded the battery port connections through the hole and on the newly glued in place battery port.
Step 9: Tips!
- If things don't work, take your voltmeter and touch different places in your circuit in order to ensure that there is a steady current throughout the system.
- Detach and reattach everything if there is a connection problem.
- Take your time and run the system through in your head after making any changes to make sure you are safe.
- Ask me questions! It's really hard to make entirely cohesive instructions.