[sdiy] How to discharge a capacitor ?

[Magnus Danielson]

From: megaohm <megaohm1 at gmail.com>
Subject: Re: [sdiy] How to discharge a capacitor ?
Date: Tue, 15 Nov 2005 18:32:44 -0600
Message-ID: <a6fac3a00511151632o19d368efh2710411f9900e920 at mail.gmail.com>

> I'll try and be more specific:
>   Let's say I want to discharge a 4700uF electrolytic capacitor. There are a
> couple in the power supply portion of the circuit. Do I take one end of the
> resistor and attach it to the negative leg of the cap, then take the other
> end of the resistor and attach it to the positive leg of the cap? What size
> resistor do you suggest? What power rating should the resistor have? There
> are also some larger and smaller caps, will the same resistor work for them?
> Or should it be larger, smaller, different power rating?

Depending on the resistance you need different power-rating on the resistor.
The issue is really time, how long shall it take. Also, if you have a very
large resistance, the internal leakage will be the major part anyway.
Also, how long time can it take? Half-a-sec or half-a-year? The decay-time is
certainly an issue, and the voltage you want to discharge.... 

Cheers,
Magnus

>  peng
> 
>  On 11/15/05, Batz Goodfortune <batzman-nr at all-electric.com> wrote:
> >
> > Y-ellow All.
> >
> > At 03:30 PM 11/15/05 -0800, Harry Bissell Jr wrote:
> > >megaohm <megaohm1 at gmail.com> wrote:
> > >> Sort of an "idiot's guide" to discharging caps. This would be
> > >> immensly helpful.
> > >That'd be EASY.
> > >
> > >Discharge them with a screwdriver... ;^P
> >
> > And if you don't have a screwdriver, the old standby of sticking your
> > tongue across the terminals is often workable.
> >
> > I have a mate who once claimed he could measure up to 50 volts with his
> > tongue. His tongue was accurate to within about 1% but got a bit
> > non-linear
> > after about 35 volts. Mind you he was also the engineer who claimed...
> > "There is no part of the human body that cannot be used in the
> > pursuit of electronic engineering."
> >
> > And I'll leave the rest to your imagination.
> >
> > NOTE: Leave the bleed resistor on the cap for a while, they have a nasty
> > habit of self charging. Something else Nige could tell you about at
> > length.
> >
> > Be absolutely Icebox.
> >
> > _ __ _ __International Pain-in-the-Ass and prophet of doom__
> > | "_ \ | |
> > | |_)/ __ _| |_ ____ ALL ELECTRIC KITCHEN
> > | _ \ / _` | __|___ |Your source of Armageddon in a musically crass world
> > | |_) | (_| | |_ / /
> > |_,__/ \__,_|\__|/ / Disgusting-> http://all-electric.com
> > / ,__ Music-> http://all-electric.com/music_downloads.html
> > Goodfortune |_____| Cult -----> http://www.subgenius.com
> >
> >