Hello everyone! Welcome back to another Ben Builds Instructable!
Today we make a homemade coilgun from parts laying around the shop. Using some capacitors and a switch and some other parts, we create an electromagnetic launcher capable to launching a small sharpened nail ~10ft using just the power of electromagnetism.
Lets get started!
Step 1: Watch the Video
First things first, watch the video above to learn about the project and to see the coilgun in action! For more detailed instructions, follow along with the Instructable!
Step 2: Gather Materials
You are going to need some materials for this project:
8 - Large Capacitors
I used 3,300 uF 40v Cornell Dubilier caps- the key here is: lower voltage = less danger so look for something in the 30 - 50v range. As for the capacitance, the bigger the better :D
1 - Large High Current Switch
1 - Coil made from ~18 AWG wire; ~20 turns
Copper Sheet and/or thick gauge copper wire
Step 3: Glue Capacitors Together
Take your 8 capacitors and glue them together so that the positive lead line up in the middle. Glue them first into four groups of two. Then take two groups of two and glue them together. Glue the other two groups of tow together end to end into a group of four.
You should now have two groups of four. Take these groups and stack them on top of each other allowing them to nest together.
Step 4: Assemble the Capacitor Bank
The image above is what the completely glued bank should look like.
Now take the positive leads and bend them together and solder them down to some copper bus. This can either be some copper sheet or a thick wire.
Step 5: Solder Copper Busses
Use augmented heat if necessary (SMALL heat gun) to warm up the copper busses and solder the capacitor leads to them.
Above is what my bank looks like with this step completed.
Step 6: Solder Negative Bus Wire
Take another thick conductor, I used heavy gauge insulated copper wire, and strip off some the insulation.
The insulation should be stripped off where the wire goes pas a capacitor lead.
When the wire is stripped, bend it into the pattern that allows it to most efficiently cover the distance from one end of the bank to the other.
Solder it in place. Augmented heat was not necessary for me in this step, but I did use a 150w soldering station, so for some it may be necessary.
Step 7: Prepare Projectile
Next, prepare a suitable projectile for the coil. I wound my coil around a relay coil spool; therefore, I used a small straw as the barrel for my coil.
As a consequence, my projectile needed to fit into a straw. I took a nail and cut it about 3cm long, with the pointed end still attached.
I took the nail over to my bench sander and sharpened it to a very fine point.
Step 8: Find a Suitable Switch
Next, I needed a way dump the capacitor bank charge into the coil.
Most people use an SCR to fill this need. I chose to make the project simpler by just using a heavy duty switch,
This switch has three current markings on it: 14.2 A, 15 A, and 500 A. My math shows about 40 A of peak current for about a millisecond or so, so it should be fine.
NOTE- Don't use my switch method if you decide to make the capacitor bank bigger. I was pushing my luck as it was. Luckily everything went fine, but you wouldn't want the switch blowing up because it was a 1 A switch that you dumped 300 A into!
Step 9: Wind Coil
We're almost done. Time to wind the coil.
I actually tried three different windings and found out that ~20 turns of insulated 16 or 18 AWG wire works best.
I unwound an old relay coil and used the spool to wind this new coil.
I put a small straw through the center of the coil and capped one end closed with hot glue.
Step 10: Assemble According to Schematic
Now that you have all the pieces done, use a terminal strip to connect everything together. Follow the schematic if you have any any issues, and feel free to leave a comment if you need any help!
Step 11: FIRE! + Safety
Congratulations! Thats it! Use a power supply to charge your bank below the maximum voltage. I charged my 40v caps to 38v.
Load the projectile into the straw and push the button. Current will surge into the coil and it will shoot the nail out of the straw at a nice clip!
BE CAREFUL- Even though this is "low voltage" and probably can't kill you, it still has the potential to scare the living daylights out of you! The second picture above is what happens if you connect the positive and negative together accidentally! The giant spark is accompanied by a bang loud enough to make the neighbors think you opened a shooting gallery in the garage!
Have fun, stay safe, and thanks for reading and watching!