capacitor charging circuit wanted

[vehemt]

Is anybody able to design a circuit that can charge a 9400mfd 200v capacitor in under 10(preferrably 5) seconds from a portable battery source? I am willing to offer monetary compensation for said circuit design(15-20usd sound ok?).
Thanks

[Tuatara]

Unnecessary.
Buy a 12V to 110V inverter from your local electronics or automotive shop. Rectify output. Attach caps. A 100W inverter will have your caps charged in about 1 second.

Any cheap and nasty inverter will do - it doesn't have to have 'sine wave' output, or fancy harmonic filters.

[vehemt]

I dont understand what you mean by rectifying output. Since the inverter will only raise the voltage to 110 does this mean modifying the circuit(changing component values) to up the voltage to 200?
thanks

[Tuatara]

Rectify means add a diode. 110VAC has a peak voltage of 155V, so you will get 155VDC on your capacitor.

It may be possible to modify the output of the inverter, but don't count on it.

What is the V rating of your caps? Because if it says 200V on the label, then you don't want to go much over 180V with a simple charger.

Secondly, what is your level of electronics expertise? 9000uF charged to 200V is at least as dangerous to your health as a pile of AP. If it doesn't stop your heart, it will still do very nasty things to your fingers.

[vehemt]

I have a pretty basic knowledge of electronics and common sense.
Cap is rated at 200v and 250v surge.
I guess I can buy a 12 to 220 inverter but then I would need to limit the voltage. How can that be done?
thanks for your replies

[Child-of-Bodom]

Hi!
What is very easy and cost effective is to buy a throw-away photocamera, get the circuit out and cut the cap off. Now attach your cap to the ends left by the former cap.
By a high and irritant vioce your cap will be loaded. There is no thread for overloading, the original cap is charged to 300V, but when I attached 3x63V, it kept constant at 189V.

Another solution is, if you want it faster, to open a 12V driven TL or neon lamp, this will cost around 11$. There is an inverter inside which transformes up to 900V AC. Buy two 1KV diodes to rectify, they cost 10cents each. (since 900V AC is 1200V DC!!) Simply attach you cap and monitor the voltage.

Where do you want to use it for? EBW? Then you have to use MPK caps as problaby known...electrolytes suck therefore. (I wasted about 20$ :mad: )

Be indeed very carefull with those caps!! W=1/2 x C x V² So your cap gives an impressive 200 Joules!! That one must be capable of instantly vapourising a piece of soldering tin what is shortcutted...
I know that a 180V 480uF cap charged to ~¾ caused an inmovable hand for about 5 min. (not my hand...)
Even the small cap of the throw-away camera bites nastly AFTER discharging via the flash tube...I found out...

I hope I helped you a little,

COB

[Doug]

I have a pretty basic knowledge of electronics and common sense.
Cap is rated at 200v and 250v surge.
I guess I can buy a 12 to 220 inverter but then I would need to limit the voltage. How can that be done?
thanks for your replies

I assume you're going for 220V inverter as that's the line voltage in Canada? You could just use a half wave rectifier circuit which if my calculation is correct will give you a peak voltage output of 155V.

[Tuatara]

NO! Half-wave rectification still gives the same peak voltage - just with more ripple.

Try attached schematic for a voltage cut-off. This is untested, of course ( I cooked it up in about 5 minutes). The parts are all very common types. Essentially the voltage from the divider across the cap is compared to half the battery voltage (~6V), and when it is larger, the relay turns off, cutting power to the inverter.

If the battery is at 12V the charge will cut off at 204 volts. Lead acid batteries can be as high as 13.5V, so you may wish to increase the 330k resistor to 390k or 470k to drop the cuttoff voltage.

[Doug]

NO! Half-wave rectification still gives the same peak voltage - just with more ripple.

My apologies, I've looked it over again and realised my flawed calculation. It's been a while since I did rectification, didn't realise how rusty I was...

Just a thought, have you already sourced the capacitor or would it be easier to just get a 350V one?

[vehemt]

Bought the cap last year.
Line voltage in Canada is 110 but I will buy a 12 to 220 inverter online.
Tuatara, thank you very much for the voltage limiting schematic.

[Tuatara]

I forgot to add a diode across the relay coil, cathode to positive suypply. This stops the back emf from the coil zapping the transistor when it turns off.
1N4001 would do for this.

[Jumala]

Hallo vehemt
I saw your nick last a few years ago when the forum was still small and concise.
The attached file is a simple 12V to 200-250V transformer circuit including voltage limiter, oscillator...
I made this plan and a sample for testing some time ago. It is made only from cheap standart parts. (no ferrit transformer or coil winding)
You can use a larger transformer like 4,5VA for faster charging.
If you need more voltage you can use a voltage doubler instead of a bridge rectifier.
I hope it is useful for you.

[Centimeter]

I recently purchased 12 used 2kv/2uF pulse discharge mica-paper polymer capacitors from Cornell Dubilier. I am planning on setting them up so as to create an over all bank value of 12kv/2uF. Is this the best configuration for EBW purposes? I am looking for as loud and visualy impresive an explosion as possible. Is this type of capacitor bank that I am looking for or should I send them back and look for different caps? I purchased a 9kv DC transformer that steps up from 150V AC. I also bought a tungsten spark gap and two high voltage diodes. I would like for the whole thing to be powered by a hand crank generator. How would I go about attaching the hand crank generator to the transformer? Should I put a capacitor in the circuit so as to even out the voltage? For the overall circuit, would a basic RC charging circuit be fine and if so what kind of resistor should I use for such high voltage operation? I would also like to be able to attach a conductivity meter so I can see when the caps are charged. I am not sue where the meter should go. I want to make the spark gap operated by a trigger. Would a piezo igniter for grills work? Any and all help is most apreciated. :)