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Charging circuit

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Turkey9

Mon Oct 31 2011, 04:46AM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

Woah woah woah. Is your capacitor ground connected to your -12V? If it's not, it should be. You need to have a common ground for the entire circuit. If you don't, then there is no return path for the current going to the sensing circuit and it won't work. Thinking on it now, this would cause all of your symptoms.

ZakWolf

Mon Oct 31 2011, 06:13AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

Thanks i will check it out tomorrow, gotta catch some Z's

Forty

Mon Oct 31 2011, 05:35PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

the switch has to be open to charge, closed to not charge, so you want to use a normally closed switch.

ZakWolf

Mon Oct 31 2011, 06:01PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

That makes sense

EDIT: I was cut short by my teacher, so thatâ€™s why is doesnâ€™t charge when i connect it (palm face slap)

So I am going to rebuild it, I have spare parts. Iâ€™m going to leave out the led comparator. For the diodes will 1n4007's work?

Inducktion

Mon Oct 31 2011, 06:31PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

No. All of the diodes in the circuit are designated to be ultra-fast diodes. Go for UF4007's. 1N4007's will overheat and die.

ZakWolf

Mon Oct 31 2011, 11:20PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

I cant use 1n4007's for the diodes that hold the gates low?

Im gonna rebuild it with out the led section, and see how it goes.

EDIT: I removed the led half and it works :D !! thanks for all the help

EDIT EDIT: What would be a good protection diode rating? My cap voltage will be 400v.

I heard they cause suck back?

ZakWolf

Tue Nov 01 2011, 04:47AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
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Posts: 608

I built the other half, with the leds, and both turn on when charging, one turns off for one second and then comes back on.

Whats the dealio?

Forty

Tue Nov 01 2011, 05:24AM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

-check that the comparators and transistors are hooked up properly (sometimes different transistor models are EBC or CBE)
-do the voltage divider calculations from the circuit diagram to see what voltage everything is 'supposed' to be at and then test yours with a multimeter and compare.
-uzzors current design has a minimum shut off of 380v, so any little variation in your resistors might swing that up over 400v and thus not shut off when you want it to. I was in the process of redesigning that trimpot section to allow for a greater range of voltage. I can't seem to remember the exact equations to set up your own interval but i see from some of my notes that:
for a range of 200v to 350v you'll want to replace the 5.6k resistor with a ~7.25k and the 1k trimpot with a ~5.44k

I don't remember how i derived that so it may be incorrect.

I'll be figuring it out again soon so i'll let you know.

I've never got the damn indicator/shut off part working either.

ZakWolf

Tue Nov 01 2011, 06:20AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

-check that the comparators and transistors are hooked up properly (sometimes different transistor models are EBC or CBE)
-do the voltage divider calculations from the circuit diagram to see what voltage everything is 'supposed' to be at and then test yours with a multimeter and compare.
-uzzors current design has a minimum shut off of 380v, so any little variation in your resistors might swing that up over 400v and thus not shut off when you want it to. I was in the process of redesigning that trimpot section to allow for a greater range of voltage. I can't seem to remember the exact equations to set up your own interval but i see from some of my notes that:
for a range of 200v to 350v you'll want to replace the 5.6k resistor with a ~7.25k and the 1k trimpot with a ~5.44k

I don't remember how i derived that so it may be incorrect.

I'll be figuring it out again soon so i'll let you know.

I've never got the damn indicator/shut off part working either.

I got it to work. Check the edits of the above post, all is well.

I also got the indicators to work sorta.

Heres the set up; I have two leds stacked in a plastic case. The Bottom one is the one thats on when charging hasn't started, when i start the charging the bottom one is on for about 2 sec then the top one switches on, then after about 2 more sec the top one shuts off and the bottom one is back on when charging is complete.

I hope you got all that. So it (B=bottom) (T=top) B-T-B.

Why does it do that? this is one trick circuit :|

ZakWolf

Wed Nov 02 2011, 01:42AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

So I dont have a protection diode yet can i still fire the gun without it?

And how do i wire the SCR? can i use this

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