Step 4: Bring It All Together

Picture of Bring It All Together
Picture Diagram Basic Coilgun.bmp
Schematic Basic Coilgun SCR.jpg
Now Connect Everything Together. Follow the Picture Diagram and Schematic.

Test the system, if it works use Plexiglas, wood, or even metal to make housing for your gun depending on the desired size/weight etc.

The Battery Banks Must not exceed +3V for relatively safe operation.
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in the first diagram you show a "charging switch" but in the second there isn't one is the switch necessary
is using a short (4 inch) coil more effective than a longer (1 foot) coil
mwgelber4 years ago
how much voltage/current should the relay be able to handle?
ThomasRex5 years ago
I wanted to make one like the pistol just a single coil should i use the second picture?
If you just want to make a simple one, and it's your first time, go with the first picture - it's by far the simplest.
RICEKING2124 years ago
For my coil gun, I'm planning to use 12 400v 150mf capacitors. With these capacitors, what kind of diode could I use to prevent the capacitors from getting damaged? Also, with these capacitors, how many charger circuits would I need? Lastly, would I have to get a better relay than the one used in this instructable? Thank you for your time.
You don't "really" need a diode - it's just a safety measure. it's stated on the last page that this does decrease velocity/efficiency. to choose a diode though, it really matters how many volts you are charging your caps up to - all in parallel? all in series?

Also, you "really" only need one charger circuit, as they can provide enough voltage, however, the more the merrier (to a point!), as they would charge your caps faster. one charger for 12 of those caps would take quite a while to charge. just try it with say... 12? you can always add more chargers.

for the relay, you would probably have to get a better one, but it depends on your voltage, and amperage. you can just find one for over however many volts you use, and for a high number of amps - maybe 50? This would be important, as you don't want your relay to fuse!

Let me know if you have any more questions :D
Where would you attach a voltmeter in this circuit?
rocket_man4 years ago
anyone have an idea on how i would go about making a cap meter that also regulates the voltage once it hits lets say 200Vs
aeronut015 years ago
Why is high voltage positive connected to input voltage negative? Won't that fry the charger?
ThomasRex5 years ago
I have never made a coil gun before should i make it look like the second picture or like the third.
Can you use a SCR instead of a relay?
skiz19895 years ago

Whats the point of D1?....is it to make sure the current will always flow one way?...or does it prevent "suck back"?

moshee skiz19895 years ago
 It's to prevent "back EMF" which can damage the capacitors and possibly blow them up.
Barrettkg5 years ago
I am confued with the switch that starts the capacitors to charge... In the instructable it says to use a DPDT switch (which i have never used before) and I do not know what to do with all 6 of those pins!!!
My question is either how would you wire that switch or could if I just resort to my good ole friend SPST? Much appreciated
dumdog9275 years ago
 ok so i made my coilgun but it doesnt have the high pitched screetch when i try to charge it and the aa batterys are hot what does this mean? i can barely hear the screech i used to hear it louder :( need answers soon this is for a science project
rwilsford07 (author)  dumdog9275 years ago
How many mini chargers do you have, how many AA's are you using, and what is your capacitor bank's properties?
 ok i have 8 120 uf cappaciters in parralell with 2 chargers and 2 aa berteries idk why but it wont charge.. a year ago i made a coilgun like this one and it worked fine and it could charge with the high pitch screech. this current one nyou have to put your ear on it to barely hear it
rwilsford07 (author)  dumdog9275 years ago
It may just be the charger circuits, some of them have a tendency to not work. After all the are meant to be disposable. Test each charger by itself with just one of the 120uf capacitors and the 2 AA in series and see if they both work, both not work, or just one of them doesn't work.
skiz19895 years ago

If i wanted to add a light to the circuit to show when its charging/charged. Where would i connect it too?

ATM i have:
batt pack >> switch >> charger circuit >> caps

In that sequence where would i add it? WOuld it operate like the light on cameras where it flashes to indicate charging and solid to indicate charged?

rwilsford07 (author)  skiz19895 years ago
simply putting a resistor and LED at the terminals of the battery would allow you to see the charge state via the LED's brightness. Look at my PA-III Design:

riku15 years ago
i dont know where it would connect
i would appriciate it if you could include instructions for modding a camra circut with only 4 lead wires to the transformers
riku15 years ago
i just came up with a way to simplify your design into one using the trigger of a drill that has reverse and foward by hooking up the capacitors up to where the power sorce was and the charger circuit tothe wires for reverse and the coil upto the fowardwires
Someone PLEASE tell me why in the schematic the high-voltage positive line, meets with the negative line connected to the battery bank... this makes it seem very likely that it is going to blow up the battery or something.

Someone please explain this... I always sucked in school at reading circuit schematics... but this makes no sense to me unless I'm missing something really important.
rwilsford07 (author)  pyromaster1145 years ago
The charger circuit actually produces a negative output voltage, so the negative side of the capacitors is actually at -330V, or whatever voltage you charge you cap to, and the positive side is at 0V. What matters here is the voltage difference, which is 330V when the negative side is at -330V.
Are you absolutely sure? I'm using a fujifilm  charger camera charger for my coilgun. Since we're dealing with such high voltage the batteries would cause a lot of trouble if they exploded. Plz help?
Oh... so in other words it's just obeying the standard idea of grounding everything that's at 0V (or whatever you want to call ground) to the ground of your power source? (And if I left it out it wouldn't necessarily do anything bad... might result in uneven voltages though because of a lack of a ground maybe?)
moshee6 years ago
Generally, do the SCR's need to be heatsinked?
rwilsford07 (author)  moshee5 years ago
No, the only thing that matters is the thermal resistance from the junction to the case, which a heat sink will not affect.
it would be better for it
hay rwilsford07 I'm cool with all the circuitry and the concepts but I am having a hard time making the gun magazine pleas reply thanx
stickeater6 years ago
thank you thank you.i just finished building mine and it worked i didnt even see the nail shoot out IT WAS SO COOL!!!!!!!!!!!!!!!
Mw4rD6 years ago
what did you use as the material for the coil? or was it just copper wire?
rwilsford07 (author)  Mw4rD6 years ago
The coil is made from Magnet Wire, normal wire does not work as well for this application.
i was wondering what AWG/ gauge magnet wire, i have seen a lot of people who make efficient coilguns use 22 awg/gauge.
skiz19896 years ago
Me again :D What are the specs of D1? ALSO Kudos on your other projects mate, saw your site and has some REALLY nice designs. Semi Auto, Multistage coils will be the NEXT step after i experiemnt with both your coil gun and DC booster. I noticed a little repetition in your booster design and coil in regards to LED placement. Ill need to tweak those around as i plan on making the LED's visible. ALSO the larger the battery bank is (not in voltage but in stored energy) does that mean the caps will charge faster? Or is charge speed based on voltage? Thanks for the help mate, Truly a great instructable.
rwilsford07 (author)  skiz19896 years ago
Thanks!! D1 depends on your capacitor bank, switching, and coil properties. For the Camera Charger the large the 3V bank is the faster your capacitors will charge. For my boost converter voltage is the primary output power determinate.
kjjohn6 years ago
I have a few questions about transistors for switching. I asked earlier if I could use a power mosfet, you said with a 1 ohm resistor. How many watts does the resistor have to be? Or doesn't it matter? Also, what kind of diode/how big should I use for a power mosfet?
kjjohn kjjohn6 years ago
also, wont the diode take away from performance?
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