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Trying to understand capacitor's

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blade20034

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Hi guys new here i have done electronics back in high school so about 5 years ago lol i know that they do but ill explain a bit more im building a coil gun and ive noticed you can get all different type of capacitors my question is why is every one using heaps of small ones instead of a big one im looking at using a car amp Power Capacitor 2 FARAD heres the specks on it
- Voltage 20V Max
- E.S.R. < 00198 Ohm
@ 25C 120 Hz
- Capability 2,000,000 uF
- 4 Digit Red L.E.D. Digital Display
- 2 x Blue Status L.E.D's
- Mounting Hardware
- Height: 30cm, Width: 7.5cm

can any one see a problem with me running one off these for a coil gun? is to much power and blow it to bits?
 
I believe you are mistaken...

What's the point of using a flash camera except to get high voltage?
 
I believe you are mistaken...

What's the point of using a flash camera except to get high voltage?
ok this is how it work the flash camara has a capcitor in it you get a few off them to gether and link them up than you run them though a coil system and make launch of the projectile
**broken link removed**
 
The energy in the projectile is going to be related to the energy dumped into it. The energy in a cap is ½CV². The constant is the energy density of the package; the more farads, the fewer volts in a particular package.

In your case, the coil winding resistance has to be smaller because of the lower voltage. You might want to try something like a single turn. Wind the coil then cut it along the length of the launch tube. Then solder the pieces back together so you end up with a single turn made of multiple pieces of heavy gauge wire. That will allow the cap to dump its charge in the shortest possible time. The length of tube covered in windings and the size of the slug being accelerated will be maximized when the slug reaches the center of the coil as the current reaches zero at about 5 RLC TC. The handicap you are giving yourself by using a large size/low voltage cap is that the values of R and L have to be minute to get the cap to discharge quickly enough. You can, of course, compensate by making the launch tube longer but, then you are losing energy to friction.

By the way, be careful with that thing. With a cap that size, you are talking about something that could qualify as a rail gun. Tune it right and fire it in a vacuum or at least a low pressure box, I see no reason why you shouldn’t be able to get a projectile at least into the transonic range. In theory, you could get a small one into the hypersonic range.
 
Thanks with that great read up on it all im going to be taking my time to build this project it would be good if i could get it up to transonic speeds
 
Think of a capacitor as a bucket of water. You can dump the water out of a 1 gallon bucket faster than a 5 gallon bucket.

If you have 5 capacitors in parallel and 1 large capacitor that is equal to those 5 caps the group of 5 will discharge faster than the single larger capacitor. If you have a circuit that required the caps to discharge fast like a coil gun or rail gun a group of smaller caps works best.
 
well most coil guns ive seen people make work of disposable flash cameras so i would say yes heres what a few people run 22,000uf/75V capacitors

The cameras only have a 1 1/2V battery, but the caps store around 300V made from the circuit in the camera.
 
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