Capacitor charger for multi stage coilgun
Dédé!, Fri Nov 28 2014, 08:42PMI want to charge and discharge the capacitors for a multi stage coilgun independently, but this requires a seperate voltage reference for every capacitor. I've modified the schematic for uzzors's cfpr cap charger to be able to do this and came up with this:
I do not know for sure if it works or not and I also dont know for sure if the charger has to be disconnected from the caps or turned off when it discharges. That's why I would like you to check if this schematic will work.
Thanks in advance,
Dehim Verveen
Re: Capacitor charger for multi stage coilgun
hen918, Sat Nov 29 2014, 06:05PM
Don't know about the rest of that circuit, but with a 12v supply the open voltage coming of of the flyback is going to be much higher than 1KV, due to the resonant rise in the primary, so you'll need to be careful with that MOSFET!
hen918, Sat Nov 29 2014, 06:05PM
Don't know about the rest of that circuit, but with a 12v supply the open voltage coming of of the flyback is going to be much higher than 1KV, due to the resonant rise in the primary, so you'll need to be careful with that MOSFET!
Re: Capacitor charger for multi stage coilgun
Dédé!, Sat Nov 29 2014, 06:26PM
I will check that out, thanks for the reply.
Dédé!, Sat Nov 29 2014, 06:26PM
I will check that out, thanks for the reply.
Re: Capacitor charger for multi stage coilgun
Dédé!, Wed Dec 24 2014, 11:51AM
I've tried out the schematic (I've tried it out without that diode I thought wasn't necessary.), but it doesn't work. First of all, the 2n3904 doesn't stay low, but conducts even when the desirable voltage isn't reached by any of the caps. Second, when I connect the 2n3904 to the ground, it does conduct, but when I try the rest of the schematic, the caps just charge as if they are in parallel and are charging very slowly. None of the caps stop with charging when their voltage limit is reached. Can someone please tell my why it doesn't work and what I've done wrong or is the problem the fact that I didn't use the resistor.
The mosfet I used was an ndfp03n150cg, the inverter I've used is a 74hc14n and the and gate I've used is a cd4073b.
I've checked out the breadboard several times and from what I can tell, it checks out with the schematic I made and gave you, so can someone please explain why it doesn't work if they know why?
Thanks in advance,
Dehim
Dédé!, Wed Dec 24 2014, 11:51AM
I've tried out the schematic (I've tried it out without that diode I thought wasn't necessary.), but it doesn't work. First of all, the 2n3904 doesn't stay low, but conducts even when the desirable voltage isn't reached by any of the caps. Second, when I connect the 2n3904 to the ground, it does conduct, but when I try the rest of the schematic, the caps just charge as if they are in parallel and are charging very slowly. None of the caps stop with charging when their voltage limit is reached. Can someone please tell my why it doesn't work and what I've done wrong or is the problem the fact that I didn't use the resistor.
The mosfet I used was an ndfp03n150cg, the inverter I've used is a 74hc14n and the and gate I've used is a cd4073b.
I've checked out the breadboard several times and from what I can tell, it checks out with the schematic I made and gave you, so can someone please explain why it doesn't work if they know why?
Thanks in advance,
Dehim
Re: Capacitor charger for multi stage coilgun
Electroholic, Wed Dec 24 2014, 05:43PM
Source of MOSFET not at ground, need high side gate driving.
Alternatively, if all the stages need to charge to the same voltage, you can just use a properly rated diode for each of the banks to isolate them.
Electroholic, Wed Dec 24 2014, 05:43PM
Source of MOSFET not at ground, need high side gate driving.
Alternatively, if all the stages need to charge to the same voltage, you can just use a properly rated diode for each of the banks to isolate them.
Re: Capacitor charger for multi stage coilgun
Dédé!, Thu Dec 25 2014, 10:19AM
It also gives you the extra option of charging the caps to a different voltage, so if anyone can help me out, I would really appreciate it!
Dédé!, Thu Dec 25 2014, 10:19AM
Electroholic wrote ...
Source of MOSFET not at ground, need high side gate driving.
I don't believe I have the source of the mosfet at ground, but I also don't believe I understand what You mean.Source of MOSFET not at ground, need high side gate driving.
Electroholic wrote ...
Alternatively, if all the stages need to charge to the same voltage, you can just use a properly rated diode for each of the banks to isolate them.
I've thought of that first, but I don't believe it would work, since the smaller caps would charge faster so they would reach the desired voltage before the other caps would and turn off the cap charger, before the other caps could be Fully charged. The Same thing would happen if the caps would have some charge left after discharging in the coil. That's why I need a separate voltage reference for every cap. Alternatively, if all the stages need to charge to the same voltage, you can just use a properly rated diode for each of the banks to isolate them.
It also gives you the extra option of charging the caps to a different voltage, so if anyone can help me out, I would really appreciate it!
Re: Capacitor charger for multi stage coilgun
Electroholic, Fri Dec 26 2014, 07:00AM
To turn on a MOSFET, you need to reach a certain voltage ate the gate pin with respect to source pin of said MOSFET. If source pin is not at ground, you need a way to reference your gate voltage to the varying source voltage.
And believe me, diode method will work. The cap with the lowest voltage will cet charged until all of them reach the same terminal voltage.
Electroholic, Fri Dec 26 2014, 07:00AM
To turn on a MOSFET, you need to reach a certain voltage ate the gate pin with respect to source pin of said MOSFET. If source pin is not at ground, you need a way to reference your gate voltage to the varying source voltage.
And believe me, diode method will work. The cap with the lowest voltage will cet charged until all of them reach the same terminal voltage.
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