# What to do with big capacitors?

I’ve got a couple 25,000uF 40VDC capacitors. Is there anything cool I can do with them?

Charge them up, short em out, run.

Well, you could use them for some high powered audio system.

Or you could make a giant tazer.

Better yet, charge them up and leave them on a bench top for some unsuspecting victim to touch.

My dad said back when he had electronics shop they would charge up little caps and leave them laying around for freshman to pickup.

A tack welder. Maybe even a mobile one!!!

Electrical socket + long handled needle nose pliers + safety goggles + a clear path + big capacitor under-rated for said electrical socket = Bottle Rocket++ :ahh:
-Eric

-tesla coil

-charge it up, grab a couple of friends, and take turns putting the ends on your tonge.

-same thing, but nostrils

-get some raw chicken wings and make it dance

-get a volenteer to allow the ends to be stuck in his head. (have emergency crew stand by)

-put the two ends in the pool when someone is swimming (may be dangerous)

-try to light stuff on fire with the spark (is there a spark?)

-charge it up, grab some old electronics, and watch the magic smoke!

-sell it on ebay

-compare the shock bettween that and the shock that you get from a disposeable camera flash capacitor

-give it fully charged to the newbies

-mount it on the wall, and claim you shot it when you where hunting in south africa

-chuck it at my head to disable me from comming up with any more ideas

haha please wear goggles and some thick fireproof clothes when exploding them. I exploded a tiny 100uF cap and it was messy. :eek:
Save them for some electronics projects lor… 25mF @ 40V can power a circuit for quite a while…

0.025 Farad x 40 Volt = 1 Coulomb electrical charge.

That’s one Ampere flowing for one second, or 10 mA for 100 seconds, assuming a load circuit that will draw a constant current. So yeah, that capacitor can power a small logic circuit, through an appropriately designed regulator, for at least a minute or so.

More realistically, a load circuit equivalent to a constant 2000 Ohm resistance (the path from your left index finger to your right index finger, through your body, under some conditions) would initially draw 20 milliAmperes, and this would decay exponentially with a 50 second time constant i(t) = 0.02 x exp(-t/50) where t = time in seconds and i(t) is current in Amperes ] so that after 2.5 minutes the current will be less than 1 mA and the voltage less that 0.5 Volt.

20 mA is not enough current to send your heart into ventricular fibrillation, but enough to get your attention. Look here for more on electric shock.

Staying alive near them would be pretty cool.

I wouldn’t do any of these things! Rule of thumb…if it sparks don’t put your face and especially your tongue near it!

Those are some serious caps, might make a spectacular linear power supply.

Rail Gun. Alright, they’re a bit small, depending on your number and desired power. Then again, they might be just fine and I’m just crazy… most likely the latter, I had a railgun design I was going to make for Physics extra credit that had a theoretical 1MW output.:ahh:

Those are overkill for a small railgun… There are a few sets of plans out there that can launch 1x1mm steel balls at 30+ m/s and are made out of 5 or 6 disposable cameras, I’d love to see what you can make with those!

Disposable camera capacitors are like 400 uF, I think. So with those you could make something very nice!

sorry i have no idea the power that this capacitor can dish out. I was just comming up with some random ideas that I wouldnt want anybody to take seriously.

If charged up at the max rating of 40 VDC - I don’t think they will cause anyone that much harm. Resistance of people is on the order of 50,000 ohms - 500,000 ohms. Ohms Law says Current = Volts/Resistance, therefore… at 40 Volts and 50,000 Ohms, Current should be around 0.0008 Amps, which won’t do much. It won’t get your attention until you get up to 10 mA or higher. Maybe on your tongue will the resistance be low enough to give a good tingle. I use .1 Farad capacitors in my physics class and we charge them up with 9 V and the kids handle them without any shocks; they like putting tin foil on the terminals and watching sparks.

Tesla Coil = NO (Voltage is way to high on a Tesla Coil)

Many of the other ideas mentioned just won’t work with this voltage rating of 40 VDC. You can charge it up at 6 V and run a DC item for a while. I bet it could run an iPod Shuffle for a little while??

Power stored in a Capacitor is P = 1/2 * C * V^2, so 1/2 * .025 * 40^2 = 20 W in each Cap if its fully charged up to 40 V.

One word: Boom. But if you do anything destructive, please… remember the rule of boom: If you can see it, it can kill you. So be safe in your haphazardly destructive rampage (if you’re going to do that, that is).

We use come big capacitors to make one kick’n ball.

Human body resistance can be as high as you say, but can also be much lower depending on conditions. Look here or here for some interesting discussion and examples.

You mean energy, not power. The formula above gives stored energy in Joules. And 20 Joules is more than enough to stop your heart under the right (er, wrong:ahh: ) conditions.

Actually… if you tied these all in parallel and got a large wound electromagnet, put a steel magnetized ring over a pole, and discharged the caps into the magnet, it will shoot up pretty dang far! :ahh:

btw can’t take all the credit for that, i saw it at the carnegie science museum.

-Q

Here is a low power shot from one of my projects.
There were 9 more caps in parallel for use outside.
It was very amusing.

The most power I ever used was 1KJ

Hey I got a really crazy idea :eek:

Why not just put them in a locker somewhere… and hang on to them .

You might come up with a good use for them someday.