New coil Gun
Danielle, Wed May 23 2007, 06:18AMI recently built a coilgun and voltage boost convertor I can charge my capacitor (33,000uf 400V) to 400V in 3 seconds my SCR is a hockypuck $300 1600V 5000A I was able to shoot a sharpened metal projectile 2.3g through 2 cans and into my wall after 20 shots I blew my capacitor i will bw posting pics but right now its a table top version.
Re: New coil Gun
uzzors2k, Wed May 23 2007, 06:30PM
800W boost converter, not bad. Could you post some info on it too? Were you able to measure the speed of the projectiles? Next time use inductive spike protection diodes to save your capacitor, I can't imagine a 400V, 33mF capacitor being cheap...
uzzors2k, Wed May 23 2007, 06:30PM
800W boost converter, not bad. Could you post some info on it too? Were you able to measure the speed of the projectiles? Next time use inductive spike protection diodes to save your capacitor, I can't imagine a 400V, 33mF capacitor being cheap...
Re: New coil Gun
Danielle, Wed May 23 2007, 11:34PM
The capacitor was used and had some cracks in it I think the comparitor I used failed and the voltage shot up blowing my cap and I did use a diode it was also still intact 1000V 80A
I also have 10 600V 300A IGBT modules do you think I can use those for this I could charge 2 banks of capacitors and discharge one through one and the other through the other. they are modules halfbridge. FMG2G300LS60E
[Edit: Fixed double post]
Danielle, Wed May 23 2007, 11:34PM
The capacitor was used and had some cracks in it I think the comparitor I used failed and the voltage shot up blowing my cap and I did use a diode it was also still intact 1000V 80A
I also have 10 600V 300A IGBT modules do you think I can use those for this I could charge 2 banks of capacitors and discharge one through one and the other through the other. they are modules halfbridge. FMG2G300LS60E
[Edit: Fixed double post]
Re: New coil Gun
uzzors2k, Thu May 24 2007, 03:23PM
Were you charging a 400V rated cap right up to 400 volts each time? If so, stop, only charge them to 10-20 volts under their rated voltage to ensure that they survive. Especially if they were used. Your multimeter might be off by a few volts remember? FMG2G300LS60E! what a monster, 300A continuous... Those will work for a coil gun, the peak current is 600A repetitive, so it might take even more in a single shot. Those should make a powerful multi-stage coil gun.
uzzors2k, Thu May 24 2007, 03:23PM
Were you charging a 400V rated cap right up to 400 volts each time? If so, stop, only charge them to 10-20 volts under their rated voltage to ensure that they survive. Especially if they were used. Your multimeter might be off by a few volts remember? FMG2G300LS60E! what a monster, 300A continuous... Those will work for a coil gun, the peak current is 600A repetitive, so it might take even more in a single shot. Those should make a powerful multi-stage coil gun.
Re: New coil Gun
Danielle, Fri May 25 2007, 03:14AM
I was charging it to 400V and while it was charginh the meater was giving me weird readings. Also I am running it off the wall with a transformer rated at 5A 18vAC then to 24v DC. I just got a new bridge rectifyer reted at 32A 1000V its
1.5" by 1.5" and is rated at 300A surge and is isolated with really good thermal resistance. my question is though, I built a loltage multiplyer for my DRSSTC and its output is 360VDC can I use this to charge it the rectifyers on that are 80A rated. can I do this or will I blow up something when trying to charge a verry large cap bank?
Danielle, Fri May 25 2007, 03:14AM
I was charging it to 400V and while it was charginh the meater was giving me weird readings. Also I am running it off the wall with a transformer rated at 5A 18vAC then to 24v DC. I just got a new bridge rectifyer reted at 32A 1000V its
1.5" by 1.5" and is rated at 300A surge and is isolated with really good thermal resistance. my question is though, I built a loltage multiplyer for my DRSSTC and its output is 360VDC can I use this to charge it the rectifyers on that are 80A rated. can I do this or will I blow up something when trying to charge a verry large cap bank?
Re: New coil Gun
uzzors2k, Fri May 25 2007, 12:55PM
Your meter should read a constant voltage rise because any spikes are absorbed by the massive capacitance. When charging a capacitor, the capacitor acts as a dead short for a while, then it represents less of a load with time. See RC time constant. If using a constant current source, like the boost converter charger, then the capacitor is a short the whole time. In the case with the boost converter, current is limited by the inductance, so it can supply power the whole time without exploding. But with a wall charger the capacitor will pull unlimited amounts of current when the cap is empty, and slowly draw less and less current as it fills -So use a current limiter, like 500W light bulb, lower wattage, slower charge.
uzzors2k, Fri May 25 2007, 12:55PM
Your meter should read a constant voltage rise because any spikes are absorbed by the massive capacitance. When charging a capacitor, the capacitor acts as a dead short for a while, then it represents less of a load with time. See RC time constant. If using a constant current source, like the boost converter charger, then the capacitor is a short the whole time. In the case with the boost converter, current is limited by the inductance, so it can supply power the whole time without exploding. But with a wall charger the capacitor will pull unlimited amounts of current when the cap is empty, and slowly draw less and less current as it fills -So use a current limiter, like 500W light bulb, lower wattage, slower charge.
Re: New coil Gun
Steve Conner, Fri May 25 2007, 02:30PM
Sure it wasn't a 3300uF cap? You can't charge 33000uF to 400v in a few seconds with a circuit running off a 5A, 18v supply. It needs way more power than the supply can give.
Steve Conner, Fri May 25 2007, 02:30PM
Sure it wasn't a 3300uF cap? You can't charge 33000uF to 400v in a few seconds with a circuit running off a 5A, 18v supply. It needs way more power than the supply can give.
Re: New coil Gun
Danielle, Fri May 25 2007, 02:34PM
I am sure it is 33,000uf ill send a pic when I have time I could even send a vid of it charging but I need a new cap that one blew up.
Danielle, Fri May 25 2007, 02:34PM
I am sure it is 33,000uf ill send a pic when I have time I could even send a vid of it charging but I need a new cap that one blew up.
Re: New coil Gun
Electroholic, Sat May 26 2007, 12:10AM
rocketry76, please, check your numbers...
A 33,000uf 400V lytic? its either a typo or BS.
Electroholic, Sat May 26 2007, 12:10AM
rocketry76, please, check your numbers...
A 33,000uf 400V lytic? its either a typo or BS.
Re: New coil Gun
Danielle, Sat May 26 2007, 06:05PM
Ok I was rong here is my pics of the setup it is 3300uf 450V. I have one thing to say to everyone who is staarting making coilguns, SCRs make a world of a diffrence.
*mod edit for oversized images*
Danielle, Sat May 26 2007, 06:05PM
Ok I was rong here is my pics of the setup it is 3300uf 450V. I have one thing to say to everyone who is staarting making coilguns, SCRs make a world of a diffrence.
*mod edit for oversized images*
Re: New coil Gun
Steve Ward, Sat May 26 2007, 09:03PM
You really ought to have that SCR in a clamp, not for heatsinking, but for proper internal connections (the end plates need to be compressed against the silicon wafer inside). Without a proper clamp, you run a very high risk of generating "hot spots" on the wafer which cause premature failure.
The biggest lytics ive seen are my 15,000uF 350V ones (and im sure on that one :P).
Steve Ward, Sat May 26 2007, 09:03PM
You really ought to have that SCR in a clamp, not for heatsinking, but for proper internal connections (the end plates need to be compressed against the silicon wafer inside). Without a proper clamp, you run a very high risk of generating "hot spots" on the wafer which cause premature failure.
The biggest lytics ive seen are my 15,000uF 350V ones (and im sure on that one :P).
Re: New coil Gun
Danielle, Sat May 26 2007, 11:52PM
I did have problems with the SCR one time I fired it and the wires welded to the SCR. but I put it in a regular C clamp with plexiglass in between. I didnt have it mounted in the picture.
Danielle, Sat May 26 2007, 11:52PM
I did have problems with the SCR one time I fired it and the wires welded to the SCR. but I put it in a regular C clamp with plexiglass in between. I didnt have it mounted in the picture.
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