hey hey! looks like a nice foruma nd a great place to ask some questions about something i just got interested in.

so i know a little bit about electronics not too too much, but basically my idea is for my roommates on april fools. i've heard of capacitor shocks that have switches and other complicated features but this is what i want to do.

i want to charge up a capacitor(not sure of strength) with a 9V battery, remove the batter and solder 2 wires onto the two prongs and wrap it around the backside of a doorknob. when the person touches the doorknob they will ground it and thus getting a shock.

will this design work? what kind of capacitor would you suggest? or if i am totally wrong point me in the right direction thanks all

 

"totally wrong", well mostly wrong. A capacitor will charge up only to the amount of voltage applied to it. 9 volts won't shock anyone, put your fingers across a 9v battery and see what you feel. Now touch the same battery to your tongue, feel or rather taste that?

So you will need to charge a capacitor to say at least 70 volts or so for someone to feel it and you need a lot more to really send a message. The capacitor will also need to be rated for the maximum voltage you plan to charge it to or higher, get one rated for 450vdc! You just have to figure out how you are going to find a source of high voltage DC to charge it with.

Good luck and I'm glad I'm not your room mate

 

This is not the kind of prank someone that doesn't know what they're doing should atempt, you can kill someone with it. If someone is touching a doorknob with their hand the most direct to ground conduction path is going to be through one or both of the feet, very likley this conduction path could be through the heart, stopping it.

That being said > The only safe way of doing this would be to have both conductors on the doorknob itself while the 'victim' is standing on a completly issolated mat, that way the only path the current has to flow through two points on the hand, worst that can do is burn the skin. A camera flash circuit could be used to charge a capacitor to upwards of 300 volts, but if you use too large of a capacitance you will burn skin as opposed to just wake them up, as well as still risking heart attack simply from the shock value. If you can find a refrence to a safe 'joule' level to send through a hand to stimulate a reflex action without harming the users (and provide refrences) it's easy to calculate the size of the capacitor requried to generate the charge.

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Assuming you are dry, 70V would be most likely nothing more than tingle assuming you touch it with your fingertips or palms, which are not that conductive. If they are sweaty it is a totally different source. Look I know that you want to pull a prank, but this is really not a wise one. Someone could be killed doing this. Capacitors would not be wise at all to use.

Something smarter would be to use a properly current limited high voltage supply. This I would definitely not trust you to build though considering you have limited electronics knowledge.

Just keep in mind, if you go wrong, your prank could turn into cardiac arrest. Its really a bad idea unless you do not completely know what you are doing.

 

It's too easy to store deadly amounts of energy in a high voltage capacitor. Most designs intended to annoy and not kill use an inductor.

 

i reccomend you get 7 or 8 car batteries, link them together and then use a capacitor of about 600vdc with some dynamite for the added prank.

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First off, 8*12 is only 96, which would only charge the cap to about 100vdc. Also, what is with people and dynamite?

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Souper man

Yeah, very bad idea. I have burned my finger so bad with a 300vdc 3300uf capacitor from i think a voltage supply that it turned my finger bad =( DONT MESS AROUND

 

Souper man

er, replace bad with black and charred rofl dont know how that happened...

 

Perhaps your bad finger?

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Lookie here, the prankster wants to use a capacitor and a simple 9v battery - no big deal. Use a .001 uF 1kv ceramic disc capacitor across the battery's terminals. Then remove the capacitor after allowing a 35 minute charge time and tape it to the doorknob. Set up your camcorder to record the momentous event. Enjoy the April Fool' s joke.

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That won't work, you need a DC-DC converter to increase the voltage to a shockable level.

A 200pF 6kV capacitor charged using a TV flyback transformer would do the job.

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I think it would be a great joke... on the OP.

 

this is what I found from another post...
Originally Posted by MARINE1142
A friend of mine had a pen that when you clicked it down for the ink to come out it would shock you. He would not let me take it apart to see what was inside does anyone know what was inthere. I was thinking a battery and a cap and the leds hooked up to the metel pen and the other on a switch up top but what size cap and what size battery?

ANSWER:
i have that pen and that game with the 4 controllers and they both are great

its a step up transformer circuit
the voltage is boosted and the amperage stays at about 0.01 amps

DOORKNOB:
How you hook up something like the 4 controllers or the pen clicker to do the same to a doorknob is beyond me... BUT i want to know as well... We are doing a "Door Project" for a design class i'm taking... I wanted to make a shocking door.

Here's a link to the type of shock I'm looking for to put in my doorknob:
http://www.spencersonline.com/index....-7603e4d8f9c9/

now can you tell me how to do it
thanks ahead of time

 

how about a camera flash