DIY Easy Coilgun | Electronic Projectile Launcher




Introduction: DIY Easy Coilgun | Electronic Projectile Launcher

About: I'm 16 years old and live in Bradenton, Florida. I like Ham Radio, very fast SBC's, and giant capacitors! Also a bunch of other stuff that I can't think of right now :)

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!




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22 Discussions


4 months ago

You would get better soldering results and expose your capacitors to less heat if you cleaned the oxide off your parts before you solder them.

Very interesting project, but you can't actually copyright such a simple design and legally speaking it is illegal to add the (c) to something that isn't legally copyrighted such as this.

you have enough amps to kill ten people with this experiment! the risk factor is completely off the charts. only do this if YOU KNOW WHAT YOU ARE DOING!!!!!!!! do not die.

Thank you for this new coil gun DIY. Nobody has done this in a long time

hey, so i was thinking of building one of these for my gr11 physics project. i saw you were using 8 40v 3300uF(<10 joules of energy) capacitors and i was wondering if it would work for me to use 4 400v 4700uF capacitors(960 joules of energy). im planning to use a bigger barrel and projectile also but if this would work for me, what would i have to modify in the circuit? would it melt the wires or be too much? and is a hollow metal barrel better or a hollow carbon fiber barrel that is thinner? and for the coil is it better to use long thin with many windings or short thicker and less windings? sorry for all the questions

2 replies

and for charging i would have to get something to stepup the voltage to 400v right? or how would i go about that

and for charging i would have to get something to stepup the voltage to 400v right? or how would i go about that

spoke too soon, different switch seems to have helped. Now MORE VOLTS IGOR!!! MORE VOLTS!!! BWAHAahaha

1 reply

Haha, glad the new switch worked out! Just be careful that you don't use too many volts, or the charge could arc over the switch contacts.

Yeah, me thinks the coil may be too big. Not sure though. I charged the caps to 25 volts (half I know) and threw the switch and......nada. drained the caps alright just didnt discharge the projectile, not even a little. I would think even at 25 volts something would have happened. Please enlighten me on my mistakes :-(

I think the son of a friend tried making one of these, or something similar... One side note, from the safety standpoint.. Anything above 40V, should be handled with gloves, and the old Amateur radio safety tip, Keep one hand in your pocket! NEVER let 40VDC (and I think same AC) or higher touch one hand and the other, or it could be lights-out for the person doing the experiment. It could react like a defibrillator, and stop the heart!

4 replies

Thats 100% correct- except... current is a function of voltage. Ohms law says that I = E/R so current is voltage over resistance. If we look up the resistance of the body from hand to hand we get the value of 100,000 ohms.


So 150 = E/100000 assuming everything is dry.

If we solve for E we get 15 million volts... not 40 :)

Still, I totally agree with you that it's better to safe than sorry.

Car coils are 12v bumped up to about 7000v and give you a nice snap.

Electric fences for stock about the same . Both give but little current

However you look at it 100 mA might kill you but I've had a few of the above and I'm still kicking . Got one yesterday as I worked on a 240 Volt compressor . Turned it off at the wall but the start and run capacitors were still charged -wow

I agree with you 100% that being as safe as possible is always the best option, but... I still have to disagree about the 40v. I = E/R and in an absolute worst case scenario where I coated my hands in salt water, was bleeding, and touched the leads, the resistance from hand to hand would be 1k ohm. I = E/R so I = 40/1000. We solve for I and get a current of 40ma. That would be a strong, strong shock and would hurt like heck, but wouldn't kill me. Assuming normal conditions of dry non punctured skin, we get I = 40/100000 and that gets me 1/2ma or basically nothing.

Still I will always be as safe a possible, wouldn't want to risk anything!


2 years ago


Neat little project. For a second I thought your brown wire was thin copper pipe and thought, "this kid just blew himself up..."

Do you know where I might be able to salvage capacitors of that size?

1 reply

Actually, because the cap bank is only charged to 38v, it would be kind of hard to blow yourself up unless you touched the wires together in front of your face.

I got my caps from marine inverters, but you could always check your local scrapyard adn see if they'll let you take a peak.