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1 stage CG, thyristor, I need repeated fire? (circuit help)

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PlayNice

Wed Apr 10 2013, 09:26PM

Registered Member #8032 Joined: Tue Nov 13 2012, 01:22AM
Location: Chicagoland USA
Posts: 33

I would like to make a 1 stage repeat fire CG. I would like to use 2 thyristor and non-polar caps so that energy just goes back an forth from one side of the cap to the other.

So say:
1st shot some of the Cap energy is used but the rest goes to the opposite side of the cap through thyristor #1
2nd shot energy goes the other way back into the other side of the cap through thyristor #2
3rd shot energy goes the other way again through #1 thyristor same as shot 1
4th shot is same as 2nd... and so on

each shot draining some of the total energy for my caps. Yenderson drew this for me once but its for a 2 stage, is there any way to add 2 thyristors to one coil so that 1st thyristor controls energy one way, and the 2nd thyristor controls energy the other way?

PS. this is not going to be a powerful CG, just want a small scale experiment to see the results

Wait, would just one thyristor work here? Connect caps, 1 thyristor in series, and 1 coil in series? Everytime the thyristor receives a signal from the opto switch it will fire in the reverse direction??

1354251576 6944 FT100083 Bicoil Simple

Ash Small

Thu Apr 11 2013, 12:30AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

One capacitor, one thyristor, one coil, and a double pole, double throw switch should do it, but you'd need to flick the switch between each shot. (could also be done with an H-bridge, and driver circuit if you want it fast and automated) (not a 'conventional' H-bridge, but one where the two high side transistors are connected together, and the two low side transistors are connected together, with the coil connected between the two high side emitter/sources and the two low side collector/drains, with one source/emitter and one drain/collector connected to each terminal of the capacitor.)

I can draw a sketch if required, (now I think about it you won't need the thyristor, just four transistors.....then again, I think you could use four thyristors)

I think this should work if you fire each diagonal pair together, like a conventional transistor H-bridge.

PlayNice

Thu Apr 11 2013, 02:00AM

Registered Member #8032 Joined: Tue Nov 13 2012, 01:22AM
Location: Chicagoland USA
Posts: 33

Thanks for the info and the sketch.

This would require 2 different input triggers right? I was hoping to just use one trigger from my opto switch. Any way to achiave this with one input? Or is there any SIMPLE device that can change my opto switch output into 2 oscilating signals.

And yes I would rather have this be fast and automated so the DPDT switch idea wont work.

Ash Small

Thu Apr 11 2013, 10:29AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I think something like a TL494 (or similar chip used for driving H-bridges) could be used to provide the alternating trigger pulses.

I imagine you could use any of the basic H-bridge driver circuits, but modified for this application.

I think you'd need some form of isolation for the high side thyristor drivers, Yanderson knows a lot more about driving thyristors than I do.

Yandersen

Fri Apr 12 2013, 06:31PM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Qx6, don't be too excited about oscillating circuit for multifiring. In best case you will have half energy for the second shot. If both bullets are the same, shot parameters will be way too different.
If you will put enough energy into single stage, you will recuperate insignificant amount of energy for the second shot.
Forget this stupid idea. Use it as double stage. Unless it is the problem for you to wind two coils...

Ash Small

Sat Apr 13 2013, 01:06AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Yandersen wrote ...

Qx6, don't be too excited about oscillating circuit for multifiring. In best case you will have half energy for the second shot. If both bullets are the same, shot parameters will be way too different.
If you will put enough energy into single stage, you will recuperate insignificant amount of energy for the second shot.

Surely this depends on how much energy is stored in the capacitor to start with? I agree that the energy left after each shot will be less, but if sufficient energy is stored to start with, and if resistive losses are low, then a significant amount of energy will be left.

I agree it doesn't seem to make a lot of sense, but we don't know the reasons behind this project yet.

Yandersen

Sat Apr 13 2013, 07:57AM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

I have some exp. Practical one. So just believe me.

PlayNice

Sat Oct 05 2013, 08:01AM

Registered Member #8032 Joined: Tue Nov 13 2012, 01:22AM
Location: Chicagoland USA
Posts: 33

God sorry guys I forgot I started this.

I have a weird new design for a coilgun that I would like to test out so one coil is all I can do. Space and design is the problem.

Yend, are you saying no matter how big and how much energy is in my caps after the first shot I will only have 50% or less energy? If that's the case yea there is no point in this design. I was thinking like AshSmalls that if the caps are huge I would have much more then 50% energy left after first shot

Let me know what you think please

Yandersen

Mon Oct 07 2013, 04:40AM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

The bigger the coil the more energy you will recuperate. The smaller the capacitance the more energy you will recuperate. The shorter the pulse, the more energy you will recuperate.
Simply divide your coil onto two halves to get two coils.

But I doubt you will ever do anything in your life. Still... If miracle will happen, keep repolarized cap away from the charger otherwise it will blow.

PlayNice

Tue Oct 08 2013, 03:51AM

Registered Member #8032 Joined: Tue Nov 13 2012, 01:22AM
Location: Chicagoland USA
Posts: 33

No offense Yand, but with that kinda of reply I very much doubt anyone even listens to what you have to say lol

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