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Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
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Posts: 608
DerAlbi wrote ...
If you discharge your Caps, you basically short circuit them. So you take your drawing and wipeout the Caps and replace it with a "wire". Can you imagine where the current flows? Can any of your Charger-Sources deliver more than 1A if the Caps are shorted? If yes.... well....
You have successfully "disconnected" the caps from each other, so one will not recharge the other. However you have not disconnected the charger circuit. E.g. is you have the Mains connected to the Bridgerectifier.... well... ouch^^ This would take a SCR, Mosfet, Transistor or IGBT at the common ground-connection at the caps. I would recommend the SCR - you switch your charger on, fire the SCR and it shuts off automatically after the caps are charged...
There is no mains involved i will draw up a better schematic i was in a hurry
Registered Member #3114
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This is a little more detailed. Everything used to work but then i started to burn up my diodes that were separating the banks, I have draw up a pcb and I am going to continue making this thing unless anyone sees a problem in that schematic.
I will post everything when its done in the projects section, it should turn out very nice
OK, mistakes are found. As there are no diodes antiparallel to coils, then your caps are get repolarized temporarily during the shot. When voltage inverts, unlimited current goes through the diode of the repolarized cap, bridge and secondary of the transformer. The weakiest part is probably the diode burned. The second mistake is a voltage control. You measure the voltage before the diodes separating caps from the charger - so basicly, it is just a peak value of the charging pulse, not the stationary voltage over the caps - when charging pulse is over, voltage control will read the wrong value (below the actual cap's voltage). The correct way is to control the voltage over one of the caps. I do it with the following chain: {zener-zener-zener...}-resistor1K-
optocoupler_diode-protection_diode and connect it to one of the caps. The transistor output of the optocoupler is open when voltage on the caps is at the desired level. Zeners precisely define the voltage value. Protection diode prevents current flow in the repolarized cap's state.
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
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Posts: 608
Yandersen wrote ...
OK, mistakes are found. As there are no diodes antiparallel to coils, then your caps are get repolarized temporarily during the shot. When voltage inverts, unlimited current goes through the diode of the repolarized cap, bridge and secondary of the transformer. The weakiest part is probably the diode burned. The second mistake is a voltage control. You measure the voltage before the diodes separating caps from the charger - so basicly, it is just a peak value of the charging pulse, not the stationary voltage over the caps - when charging pulse is over, voltage control will read the wrong value (below the actual cap's voltage). The correct way is to control the voltage over one of the caps. I do it with the following chain: {zener-zener-zener...}-resistor1K-
optocoupler_diode-protection_diode and connect it to one of the caps. The transistor output of the optocoupler is open when voltage on the caps is at the desired level. Zeners precisely define the voltage value. Protection diode prevents current flow in the repolarized cap's state.
Thanks Yandersen could you help me once again by drawing a simple schematic, i have a hard time turning words into a design/picture. So you have 3 zeners in series connected to a 1k resistor going to one cap and the voltage regulator?
Here is the output of the charger I use in my recoup design:
The circle separates parts located on the charger board. Charger must be stopped immidiately before the shot, MOSFET' gate grounded, and only after that shot should be performed. After the shot there must be no negative voltage left in any of the caps. If this is ensured, than open MOSFET, then start the charger. It is assumed that HV+ is the positive exit of your diode bridge, Common GND is the negative one.
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
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Yandersen wrote ...
As an example of voltage ctrl part usage, here is the simplified schematic of my flyback charger (no output mosfet ctrl circuit shown):
The DZ1 is actually 4 zeners in series (200V+200V+200V+180V) giving me around 780V level.
First off thanks for the feedback; I must say though I am confused. So i should disconnect my charging circuit form the cap bank even though its protected by the uf4007's going to each cap... It was working perfect but then there was a weird short and some sparks, everything still functioned but the diodes kept dying one after the other after each shot... O.o
Do you actually read my feedback?.. During the shot cap get REPOLARIZED - voltage inverted. Follow the current path and please, understand WHY it blows your diodes. When cap got repolarized (which is bad for cap!) unlimited current flows through the secondary of your transformer, bridge and the diode separating that cap from the others. So before the shot, charger must be switched off, then disconnected, and only after that shot can be safely performed. Jeezz...
Let's make it simple. Put a powerfull diodes antiparallel to your coils and forget about all those problems. At least your caps will live longer.
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608
Yandersen wrote ...
Do you actually read my feedback?.. During the shot cap get REPOLARIZED - voltage inverted. Follow the current path and please, understand WHY it blows your diodes. When cap got repolarized (which is bad for cap!) unlimited current flows through the secondary of your transformer, bridge and the diode separating that cap from the others. So before the shot, charger must be switched off, then disconnected, and only after that shot can be safely performed. Jeezz...
Let's make it simple. Put a powerfull diodes antiparallel to your coils and forget about all those problems. At least your caps will live longer.
If im upsetting you by asking questions on a form made for advanced and introductory questions feel free not to respond to any of them, i still appreciate the feed back once again, i hope you check out the finalized version...
Let's concentrate on topic instead of feelings as we are not the girls. :) As your caps are polar, they don't like repolarization - life time shortens, parameters quickly degrade. Antiparallel diode protects caps from that process, but slightly degrades the performance of the shot - unused energy slows down the projectile instead of dissolving electrodes of your cap. I'm against monkey-designs, you know, but I even more unhappy if I see kamikaze design of cap-killers. So after all, just put powerfull diodes antiparallel to your caps unless you are going to try non-polar ones.
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Optical trigger Tuning
