Coilgun Handgun

Step 4: Bring It All Together

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.

Comments

[crissangelic]

in the first diagram you show a "charging switch" but in the second there isn't one is the switch necessary

[crissangelic]

is using a short (4 inch) coil more effective than a longer (1 foot) coil

[mwgelber]

how much voltage/current should the relay be able to handle?

[RICEKING212]

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.

[mbrown9412]

also - that's a lot of capacitance. you don't need that much. if you have too much capacitance, the pulses on the coil last too long, and as the projectile is drawn through, it's pulled back, because the magnet is still active.

[padmanabhapsimha]

Try using SCR's or TRIAC's. They are faster and more efficient and can easily handle more surge current (10 times) more than the specified continuous current.

[mbrown9412]

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

[brooklynlord]

Can you use a SCR instead of a relay?

[brooklynlord]

nvm

[brooklynlord]

Did you use Kodak Funsavers or Kodak Max Fash (NOT Powerflash) disposable cameras for your coilgun?

[mbrown9412]

just go to target or walmart and ask for their old disposable cameras - don't tell them it's for a gun!

open up the kodak ones, and look for a similar charger to the ones in the pictures. it's kind of a blueish green, and you can tell it's right because the pinouts for the parts you cut out are correct.

[ThomasRex]

I wanted to make one like the pistol just a single coil should i use the second picture?

[mbrown9412]

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.

[Chainsaw Bear]

Where would you attach a voltmeter in this circuit?

[eggman]

using a voltmeter, right up to the capacitor in parallel.

[rocket_man]

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

[eggman]

http://www.instructables.com/id/DC-DC-HV-Boost-Converter/ the resistor divider and lm393 in this circuit do just that

[rocket_man]

yes that does what i want but also for a monitar i wanted something such as thishttp://www.youtube.com/user/HVdischarge#p/u/8/T8MlrguF7Kg the led meter

[eggman]

you can either use the lm3914, which is designed specifically for that, or you could use a resistor divider to pare down the voltage to 0-5 volts, and build an analog meter of some sort (thats what i did).

[rocket_man]

ok i like that idea and i dont want to sound like a noob but could i get a circuit design or something btw thx for the help eggman

[rocket_man]

wow im really stupid tnx eggman i just got what you ment

[aeronut01]

Why is high voltage positive connected to input voltage negative? Won't that fry the charger?

[paradox116]

Capacitors store a strong negative charge, so you could say that the positive side is the ground.

[ThomasRex]

I have never made a coil gun before should i make it look like the second picture or like the third.

[skiz1989]

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

[moshee]

 It's to prevent "back EMF" which can damage the capacitors and possibly blow them up.

[Barrettkg]

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

[eggman]

 i believe you can use a spst, all you have to do is interrupt the connection from the batteries to the chargers.

[dumdog927]

 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

[duct tape]

The batteries getting hot sounds like a short circuit.

[rwilsford07]

How many mini chargers do you have, how many AA's are you using, and what is your capacitor bank's properties?

[dumdog927]

 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]

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.

[skiz1989]

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]

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:

http://sites.google.com/site/futureexperimentalsystems/pa-3

[moshee]

 if you want to make it that fancy (flashing and solid and whatnot) you'd probably need some IC's and some logic circuits. The camera charging circuits have lights on them to indicate done charging, just use those.

[skiz1989]

problem is im wrapped those curcuits up in e-tape to insulate them.

Someone told me putting an LED just after the caps on a resistor would work?

[moshee]

 well, if you did that it would be extremely inaccurate and you might need a really big resistor. you could use a voltage comparator like the lm393, but that would take too much effort. just taking off the electrical tape would be worth it.

[mbrown9412]

each charging circuit has an LED - solder those off, and move them up top?

or you could attach some sort of comparator to the caps/ground, and hook that up to an LED

[riku1]

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