SpudFiles

Ive done it ive made one on my own coil gun
and im only 13 i kick ass and boy shes a bute. ive tested it but i need a difrent ristor for my switch a 1/2 wat but other than that it rules and let me tell you through trial and eror it was hard 2 months to build this thing.

hows the performance. ive been trying to build one with disposable cameras for a while now but the most distance i can get is like 5'.

these are aditanal photos

Nice gun, I built one similar a while back, but it had smaller capacitors.

Just wondering- what did you use for a charging circuit?

Those are some pretty beefy looking capacitors. Where did you get them?
What kind of range can you get with this thing?

Kick ass. You are a pretty clever young lad are you not
Range?

Nice i like it
I think your getting around 400V going into the coil, 2 200v caps in series(If i remember series adds voltages and parallel adds currents)., but because of the high micro farads i think the current will last a while.

I think if you made the coils longer, you would increase performance because i think as the object hits half way down the coil the magnetic field is still on in one direction, as it passes half way it will slow down because of the poles of the coil. You could probably increase the length of the coils by about 2 times. You want the capacitors to be fully discharged as the object hits half way down the coil.

Do you mind posting a schematics diagram?

-Marco321, If the two capacitors were connected in series then the voltages would add together to make 400volts but the capacitance would drop somewhat. If they are connected in parallel the voltage will stay the same but the capacitances will add togther, making 24000µF.

Depending on the resistance of the coil, it will affect how quick the capacitors will discharge if it has a very low resistance then by the time the projectile is in the center they might be completely discharged, but if a high resistance they might not discharge as quickly.

Thats what you want to aim for when designing the coil for this type of thing. The least amount of resistance possible. With less resistance equals more current which equals larger magnetic field.

-Bigger wire has less resistance but you also get less number of turns and smaller diameter is vise versa. The amount of turns directly affects the magnetic field produced. So you have to put into consideration these things. So you would want to find something in between.

Also you want to be able to dump the electricity in the capacitors as quickly as possible.

-An larger voltage is better (within reason) because a larger current will be produced.
For example if you coil has a resistance of 5ohms and you have a voltage of 200 volts then in theory (I=V/R) you should get 40amps then say you use 400 volts instead you would get 80 amps.

But ofcourse this isn't exact as it doesn't take into account the many other circumstances in the circuit, such as how the current will most likely surge and as the capacitors are discharged the overall voltage will drop.

Just a few ideas.

Sweet gun! You should make the coil about the same daimeter as the length if you want the besr performance. Even better still, cover the coil witha steel tube. It will help direct the magntetic field towads the center. Where'd you get those huge caps from?

I'm guessing he got the caps out of a full-wave rectifier of some sort (a big one).
I've heard that adding steel tubing actually decreases preformance, by the way (I was never able to tell the difference myself).

Nice gun though. I do think a bigger coil might help. Maybe 25-50% longer and twice as thick would probably boost the power a bit, especially with those huge caps.

Whoa, wait...adding 2 capacitors in series will NOT increase the voltage, all it does is increases the amount of voltage you can run across them without exceeding their tolerances. It follows the same formula as parrallel resistors.

Vice versa for parrallel caps, it adds the capacitances together.

I believe the caps also have an internal impedance which affects their discharge rate too.

Its been a few years since i last worked with electricity, apart from physics.

I have an idea on increasing performance. Why don't you make an induction coil, you can get like 10 000 volts basically constantly. Then use an IC555 chip to make a timing circuit to run the current for a certain amount of time. The induction coil will be easy to make, and the timing circuit wont require much at all. I believe there are formulas for figuring out exactly how long the circuit will run for based on the resistors and caps used on the IC555 timer.

There are plans for the timer and induction coil on the net, i have used the IC555 timer plans and almost used the induction coil plans.

Good Luck

Also note that the voltage rating of the series capacitors is equal to the sum of the voltage ratings of the individual capacitors if they are the same value (off some website)

Both of those caps are exactly the same so Im assuming this rule would apply to them and that it could be charged up to 400volts?

nz_cannons wrote:Also note that the voltage rating of the series capacitors is equal to the sum of the voltage ratings of the individual capacitors if they are the same value (off some website)

Both of those caps are exactly the same so Im assuming this rule would apply to them and that it could be charged up to 400volts?

No, the rating is added, but the voltage still depends on the source. If you have a 200V source, you'll get 100V across each cap, regardless of whether it is rated to 400V or 200V.

*You can make a voltage multiplier, which will take an AC signal and multiply it to create a DC signal of a much higher voltage, but that's much different from simply connecting them in series.

And I think 10,000 volts is a bit much for a coilgun. From what i've gathered, ~700V is a good level, although I could be wrong.

ill answer all your questions later sorry. hers a some internal photos