70V, 44000uF, Single Coil
Silas, Sun Jun 03 2007, 02:55PMHey, I'm new here, so HELLO from Denmark
I've made a couple "coilguns" from disposeable cameras, without calculating anything what so ever, and they are starting to be really BORING!
So now I wan't to move on to some more power, and tweak it to maximum.
I'm sorry if this is going to be a spoonfeeding topic, but I guess someone hopefully will have mercy, and help me out here. I've tried using Barry's calculators, but I'm confused.
Right, enough rambling, on to business.
Capacitors: 2 * 71V 22000uF
I wan't to build a single stage, portable CG, with those 2 capacitors.
Questions:
How do I calculate the right resistance for the coil?
Also, lower voltage, higher capacety = thicker, shorter wire for the coil?
How do I calculate the size of the thyristor I should use?
How would I boost the power, of say 8 AA batt. (12V) or 16 (24V), to 70 V ? Schematics please
What size diode should I use for the "freewheel" (think it's called that), and how should it be wired? Parallel to the coil?
Also, I've heard that encapsuling( washers and plumbing tube or something) the coil in metal makes it more effecient?
I'm really sorry for all the questions...
There will ofcause be pic's and video's of the progress, and finished gun..
Re: 70V, 44000uF, Single Coil
Zum Beispiel, Sun Jun 03 2007, 06:22PM
71V is really too low for an efficient gun, I'd series the caps for 140V and 11000µF.
The coil resistance shouldn't be that difficult to calculate, just get a chart with wire gauge vs. resistance/meter and multiply with lenght of wire used. Of course, the resistance of the coil isn't the only limiting factor for the current, the coils inductance matters too. The formulas for calculating the inductance are all over the net...
As for the voltage conversion, a boost converter is what you want. It should be pretty easy to build for this low power level.
And finally about the thyristor and diode: Basically you take the biggest thyristor and diode you can find. Just make sure that their breakdown voltages are above your capacitor banks voltege and that the peak current rating is large enough (bigger the better). You connect the diode in antiparallel with the coil, so that it doesnt conduct when voltage is applied to the coil (cathode to +, anode to -), but short circuits the reverse kickback.
Hope this helps.
Zum Beispiel, Sun Jun 03 2007, 06:22PM
71V is really too low for an efficient gun, I'd series the caps for 140V and 11000µF.
The coil resistance shouldn't be that difficult to calculate, just get a chart with wire gauge vs. resistance/meter and multiply with lenght of wire used. Of course, the resistance of the coil isn't the only limiting factor for the current, the coils inductance matters too. The formulas for calculating the inductance are all over the net...
As for the voltage conversion, a boost converter is what you want. It should be pretty easy to build for this low power level.
And finally about the thyristor and diode: Basically you take the biggest thyristor and diode you can find. Just make sure that their breakdown voltages are above your capacitor banks voltege and that the peak current rating is large enough (bigger the better). You connect the diode in antiparallel with the coil, so that it doesnt conduct when voltage is applied to the coil (cathode to +, anode to -), but short circuits the reverse kickback.
Hope this helps.
Re: 70V, 44000uF, Single Coil
Simon, Mon Jun 04 2007, 07:07AM
Higher capacitance means you'll have a longer pulse time if you don't reduce the inductance (coil with fewer and smaller turns). You want the pulse time to be on the same order as the time the projectile takes to pass through the coil.
Simon, Mon Jun 04 2007, 07:07AM
wrote ...
Also, I've heard that encapsuling( washers and plumbing tube or something) the coil in metal makes it more effecient?
It can make a big difference (though sometimes in the wrong direction if eddy currents take over). Have a read of the wiki page (about delta L in particular) and come back if you still have questions.Also, I've heard that encapsuling( washers and plumbing tube or something) the coil in metal makes it more effecient?
Higher capacitance means you'll have a longer pulse time if you don't reduce the inductance (coil with fewer and smaller turns). You want the pulse time to be on the same order as the time the projectile takes to pass through the coil.
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