Noob question about coils (first CG just built)
KillerRabbit, Fri May 25 2007, 02:09AMHi, I just built my first coilgun using a flash circuit from a camera. Not having the time to make a good coil myself (I did this as an in school project), I used an entire roll of 22 gauge magnet wire as my coil. The metal rod I am using (about 6cm long and 5mm in diameter) goes only about 3 feet, but I have read that it should be going much further. The circuit uses a 330v capacitor. I was thinking this was because I didn't have enough power for the coil, but then again I don't know very much beyond the basic idea of how to make a CG work. Am I right, or is it somethng else, or am I getting normal performance?
Re: Noob question about coils (first CG just built)
..., Fri May 25 2007, 02:27AM
Your coil is too big, you are getting a long, slow pulse which doesn't transfer much enerrgy into the projectile.
..., Fri May 25 2007, 02:27AM
Your coil is too big, you are getting a long, slow pulse which doesn't transfer much enerrgy into the projectile.
Re: Noob question about coils (first CG just built)
Bjørn, Fri May 25 2007, 02:37AM
When the pulse is long it is not over when the projectile passes the middle of the coil and the projectile will be slowed down.
Calculate the energy stored in the capacitor and the energy transferred to the projectile, that way you can find the efficiency and can easily track your progress. It also makes it simple to compare with other peoples results.
Bjørn, Fri May 25 2007, 02:37AM
When the pulse is long it is not over when the projectile passes the middle of the coil and the projectile will be slowed down.
Calculate the energy stored in the capacitor and the energy transferred to the projectile, that way you can find the efficiency and can easily track your progress. It also makes it simple to compare with other peoples results.
Re: Noob question about coils (first CG just built)
KillerRabbit, Fri May 25 2007, 02:47AM
Thanks very much. J/w, why do people not consider Flash Circuit CG's "real" CG's?
KillerRabbit, Fri May 25 2007, 02:47AM
Thanks very much. J/w, why do people not consider Flash Circuit CG's "real" CG's?
Re: Noob question about coils (first CG just built)
Danielle, Fri May 25 2007, 04:38AM
Thats a definition question but I built a bank of 10 camera flash caps and it shot a bb through a can and clock ed with a compensated sound trap at 63 m/s . my coil was calculated and I used a SCR and a diode across the coil. Here is a good site with calculators on coils.
http://www.coilgun.info/mark2/rlcsim.htm
http://www.coilgun.info/mark2/inductorsim.htm
Danielle, Fri May 25 2007, 04:38AM
Thats a definition question but I built a bank of 10 camera flash caps and it shot a bb through a can and clock ed with a compensated sound trap at 63 m/s . my coil was calculated and I used a SCR and a diode across the coil. Here is a good site with calculators on coils.
http://www.coilgun.info/mark2/rlcsim.htm
http://www.coilgun.info/mark2/inductorsim.htm
Re: Noob question about coils (first CG just built)
pachy, Sun May 27 2007, 10:06AM
Here you can calculate the energy stored in your capacitors: http://www.electronics2000.co.uk/calc/caclchrg.htm
pachy, Sun May 27 2007, 10:06AM
Here you can calculate the energy stored in your capacitors: http://www.electronics2000.co.uk/calc/caclchrg.htm
Re: Noob question about coils (first CG just built)
KillerRabbit, Wed May 30 2007, 01:24AM
What would be the ideal size of coil for use with a 330-volt capacitor?
KillerRabbit, Wed May 30 2007, 01:24AM
What would be the ideal size of coil for use with a 330-volt capacitor?
Re: Noob question about coils (first CG just built)
Shaun, Thu Jun 07 2007, 05:01AM
My first coil gun was mounted in a pencil box with nice little charge/on-off/fire switches. The similarity to KillerRabbitt's coil is I also used a roll of magwire as my coil, but it was 16 ga. A .75" ball bearing fit perfectly, and with a bank of 8 photoflash caps the ball woud go like 6 feet up. It was great as a demonstration, in that it was not dangerous, and totally silent. I don't know how that ever survived as long as it did, with no diode across the coil, not even an SCR, just a switch in series with the cap bank.
As far as the right size coil for a single photoflash cap, I'd say pretty d*m* small, alot smaller than a full roll of magwire. The best way is to experiment. Do some ballpark calculations, then wire it up.
Shaun, Thu Jun 07 2007, 05:01AM
My first coil gun was mounted in a pencil box with nice little charge/on-off/fire switches. The similarity to KillerRabbitt's coil is I also used a roll of magwire as my coil, but it was 16 ga. A .75" ball bearing fit perfectly, and with a bank of 8 photoflash caps the ball woud go like 6 feet up. It was great as a demonstration, in that it was not dangerous, and totally silent. I don't know how that ever survived as long as it did, with no diode across the coil, not even an SCR, just a switch in series with the cap bank.
As far as the right size coil for a single photoflash cap, I'd say pretty d*m* small, alot smaller than a full roll of magwire. The best way is to experiment. Do some ballpark calculations, then wire it up.
Re: Noob question about coils (first CG just built)
Simon, Thu Jun 07 2007, 05:40AM
I found that for a single 330V, 100uF cap from a disposable camera with my first CGs, a sewing machine bobbin full of .25mm magnet wire worked very nicely. Try to get a plastic bobbin (though I still managed to get a metal bobbin to work to ~2% efficiency).
For this low power, I think thin wire is best for highest density.
A bobbin is on the order of a cm wide and two in diameter.
Simon, Thu Jun 07 2007, 05:40AM
I found that for a single 330V, 100uF cap from a disposable camera with my first CGs, a sewing machine bobbin full of .25mm magnet wire worked very nicely. Try to get a plastic bobbin (though I still managed to get a metal bobbin to work to ~2% efficiency).
For this low power, I think thin wire is best for highest density.
A bobbin is on the order of a cm wide and two in diameter.
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