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Registered Member #4455
Joined: Sun Feb 26 2012, 12:49AM
Location:
Posts: 14
Hi, here is another question. Still using a one disposable camera and it's capacitor only. When the capacitor done charge and I manually connect the coil to the capacitor, it make a big spark at the last connection. But only some of the coil I wined, not the others.
What does that mean when the coil do the spark?
Does that mean the wire on the coil is too short? Or if its due to the wire's thickness?
Registered Member #4034
Joined: Thu Jul 28 2011, 10:41PM
Location: somewhere in the Southern hemisphere
Posts: 138
It is because several 100's of amps are being conducted through the wire in a very short time, thus causing a small amount of it to melt where you connect it (think welding). And thus if your wire has any appreciable resistance it is going to inhibit the flow of electricity and there will be less current over more time (bad for a coil gun) and this will not produce a spark (or not as an impressive one).
Registered Member #3792
Joined: Sun Mar 27 2011, 06:07PM
Location:
Posts: 136
lifa321 wrote...
So spark = good~
Well, not exactly. Sparks also mean a loss of energy that otherwise would be used to accelerate the projectile (i noticed that on the first coilguns i built). My suggestion is to invest on a thyristor switch (no sparks, better efficiency).
Registered Member #4455
Joined: Sun Feb 26 2012, 12:49AM
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Posts: 14
PSCG wrote ...
Well, not exactly. Sparks also mean a loss of energy that otherwise would be used to accelerate the projectile (i noticed that on the first coilguns i built). My suggestion is to invest on a thyristor switch (no sparks, better efficiency).
OK, thanks, I'm only using manual connection on testing. Are there any reason I should choose between To-3 or thyristor? Or they should perform the same?
Registered Member #3792
Joined: Sun Mar 27 2011, 06:07PM
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TO - 3 is a package type for semiconductors (that includes some thyristor products if you mean that). Otherwise, a BT151 series thyristor would be perfect for your low power demands.
Registered Member #3792
Joined: Sun Mar 27 2011, 06:07PM
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Posts: 136
lifa321 wrote ... Its a 2N6688 Transistor.
Since it will only be a really short time, this should work right?
No, transistors would not work. As i see, 2N6688 can handle only 50A peak current (not specified by the manual, usually over a period of 8.3 or 10 milliseconds). So, unless the peak current is less than 50A, it will blow.
On the other hand, thyristors that can handle less continuous current than this transistor can handle peak current values of 100A or more.
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Coil Connection spark when connect?
