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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Jhackulon wrote ... ...Do i just keep the capacitor in the camera circuit and short circuit the capacitor through the relay to the coil, etc, after it has charged?
Anybody ever try putting a coilgun coil in series with the flashtube in disposable camera circuit, using the tube as a triggered-spark-gap switch? In disposable cameras, the normal flashtube current is hundreds of amps for about a millisecond. Effective resistance of the tube is on the order of 1 ohm. (I think the voltage goes approximately as square root of current).
Registered Member #514
Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295
Klugesmith wrote ...
Anybody ever try putting a coilgun coil in series with the flashtube in disposable camera circuit, using the tube as a triggered-spark-gap switch?
This has been discussed before in the archives. The thing is, those flastubes are designed to burn that energy and turn it into light. The effective resistance might be a single ohm, but when you take into account the total resistance of the circuit, you can see where most of that energy is going to be burned...
Plus, at higher energies that tube is just going to turn into an accidental IED, shooting broken glass all over the place.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Sorry I overlooked the archived discussion. I brought up the idea because OP discusses using a single camera-flash capacitor. So the original flashlamp can easily dissipate all the stored energy & come back for more.
The normal flashlamp current pulse has comparable height & width to what OP expects in coil. It should be able to generate a magnetic field pulse in a solenoid almost for free, energy-wise, if the coil is wound with thicker wire so its R is much less than that of flashlamp. Could use a coil that would give a very underdamped discharge (severe voltage reversal) if the lamp were omitted. Maybe I'll try it someday.
In all coilguns except "energy recovery" configurations, the energy -not- imparted to projectile ends up heating the coil anyway. Part of that energy (peaking at 14% in a critically damped RLC) temporarily goes into the solenoidal magnetic field.
[edit] I read some of the old discussions of this topic. Not surprised to see several people reporting measurable but very poor performance using flashlamp as switch (compared to metallic contacts). Still thinking it could be an interesting challenge to optimize a coilgun based on standard camera flash - nothing added except the coil.
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Good coilgun circuit?
