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 charging capacitor bank with wall outlet?

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haxor5354



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PostSubject: charging capacitor bank with wall outlet?   Mon Jul 28, 2008 5:58 pm

would AC charge a bank of capacitors properly? and if it does charge properly, would it be instantly charged because the wall outlet provides a large current? just 1 last question, is this safe?
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PostSubject: Don't do it!   Mon Jul 28, 2008 7:12 pm

Never connect a capacitor to an AC socket. The power in the United States is 120V 60Hz AC. That means that the current is alternating at 60Hz or 60 times a second. That would mean that your capacitor would be charged/discharged 60 times a second. Not only that but as the name implies AC current alternates meaning you will reverse charge your capacitor. With electrolyte capacitors that means boom. If it could take reverse voltage like a ceramic capacitor then it would act as a short. A capacitor on a AC line is like a resistor on a DC line.

There are ways of using an AC socket to rapidly charge capacitors. I never tried them and I never plan to. Playing with AC outlets without knowing exactly what you are doing is extremely dangerous. AC can penetrate through your body a lot easier then DC meaning 120V AC is a lot worse then 120V DC. Also the large currents that an outlet can supply are extremely dangerous as well and if shorted can cause a lot of problems. If you want to use an outlet buy a transformer and then step that up with a homemade circuit like mine.

Justin
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haxor5354



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PostSubject: Re: charging capacitor bank with wall outlet?   Mon Jul 28, 2008 10:44 pm

you know those image scanners right? I found 1 on the street and took it apart, i kept the 12V to (unknown voltage to power up the florescent tube) transformer. when I use my multimeter to measure the voltage, it just shows up random things even though the range is on 1000V (and yes I tried it on DC and AC). It seems like I don't even have to hook up the multimeter's ground terminal to the ground wire of transformer to get an arc across the positive terminal of the multimeter. <is this the reason why kilo-volt meters only have 1 terminal ?>

when I was playing around with that arc with a screw driver right beside my computer, the mouse froze , then I unplugged it and plug it back in again, it works fine. I tried it at least 5 timers, and every time the mouse freezes. is it EMP of just interference like a cellphone put beside a speaker?
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PostSubject: Re: charging capacitor bank with wall outlet?   Tue Jul 29, 2008 1:02 am

I have one of those plasma globes and I was making electrical arcs with that. If I was near my computer it would reset and the audio from my speakers would get jacked up. HV arcs make large amounts of EM interference. I don't know about kilo-volt meters but even high voltage has a ground. Florescent lights take very high voltage to get the started. Don't use that for charging capacitors, but you can use it to make a cool arc. Cool

I had a HV transformer for a florescent light, 1200V. It put out AC voltage with large peaks. Using 4 HV diodes I rectified the voltage and charged some capacitors, but since it is very high voltage but not much current you don't get very much, slow charging. I also built a vandergraph generator about 2.5 feet tall and got 8-12" sparks from that. Fun stuff Smile

Justin
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haxor5354



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PostSubject: Re: charging capacitor bank with wall outlet?   Tue Jul 29, 2008 3:44 am

my screw driver isn't connected to ground, but it still arcs from positive? how and why do this happen?
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PostSubject: Re: charging capacitor bank with wall outlet?   Tue Jul 29, 2008 6:38 am

With high voltage you start dealing more with charges. The ground wire is connected to something where it can give a lot of electrons to. Something large, like the ground you stand on. The positive end is attracted to the screw driver because it has a negative charge and is full of electrons. When it arcs to the screw driver the charge is dissipated into the air allowing the spark to continue to jump to it. The charge in the air eventually makes it way back into the now negatively charged ground making a full circle.

If you connected the ground of the HV to the screw driver you could get a much more intense arc. Not recommending it though.

I am not an expert of HV so some of this could be wrong.

Justin
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haxor5354



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PostSubject: Re: charging capacitor bank with wall outlet?   Tue Jul 29, 2008 6:06 pm

another thing I want to ask, how many volts does it need to power up the xenon flash tube in a disposable camera. and would it explode after a few seconds? because it get extremely hot even after a 0.5 second flash


If AC current is at 60Hz if I add a diode to stop electrons flowing from the other way would I get a 30Hz DC current?
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PostSubject: Re: charging capacitor bank with wall outlet?   Tue Jul 29, 2008 6:53 pm

No, you will not get 30Hz DC. See here for more information.

The xenon tube is really small so a lot of power will go through it making it hot. I don't know if it will explode, only one way to find out.

The xenon light takes a very high burst of voltage to get it to light initially but after that it takes a much smaller voltage as the xenon gas is now a plasma and more electrically conductive.

Justin
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haxor5354



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PostSubject: Re: charging capacitor bank with wall outlet?   Wed Jul 30, 2008 3:42 am

I think i found 1 in an old computer power supply and another 1 in a tool box. are those rectifiers?


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PostSubject: Re: charging capacitor bank with wall outlet?   Wed Jul 30, 2008 4:46 am

Yes they are. You can also make your own with four diodes. That is what I did.
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PostSubject: Re: charging capacitor bank with wall outlet?   Wed Jul 30, 2008 2:11 pm

So, if (~) and (~) is plugged into a wall socket, it would output an DC current in (+) and (-) ?
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PostSubject: Re: charging capacitor bank with wall outlet?   Thu Jul 31, 2008 1:35 am

In theory yes. First know that it is not very good DC power. It is a series of bumps and it will have a peak voltage of 120V*1.4=168V. See here for some good info.

Another thing to consider is if your rectifier can take the voltage/current of an outlet. It is probably best to buy one with a know rating grater then anything you will through at it or make one with four diodes with the right ratings.
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