Art Needs Science

May 7, 2004 12:48 AM

Art student requests technical advice of electrical engineer (or similar) for electrical components in a sculptural installation. [details within]

In a nutshell, I'm making an electric chair.

To quell possible moral conflicts: it won't be functional, all current will be properly grounded, and no live wires will be exposed. You won't be an accomplice to accidental death and/or injury of me or others :)

I bought a cheap armchair from goodwill and I'm attaching a homemade safety switch box (a local electrical contractors' supply quoted me $70!). The illusion of danger is provided by a switch that, when activated, lights a small red lamp flush-mounted on the box.

The problem is such: I want to make the safety switch box produce the ominous 60hz buzz common to big transformers on the street.

The chair will be wired as such: 120v house current into the safety switch box that the transformer within turns to 12v dc (the rating of the switch and lamp).

I saw two options: a buzzer hooked up to the 12v, or a mini speaker hooked up to line current.

The buzzer will be too loud and too high-pitched. What can I do about this? (resistors?)

The speaker (as I understand) will draw too much current for the building's wiring (25 amps?). What can I do about this?

My electrical know-how is marginal (couldn't tell you how ohms, volts, amps, and watts matter) but I understand basic circuitry and can solder.

posted by evilbeck to science & nature (5 comments total)

I understand that a variable resistor would be of use with the speaker, however the 25 amps will still be drawn and it would produce more heat than a resistor could handle (at least, a resistor that costs less than $5).

Bonus points: photos of final product emailed to the person who answers this for me. And karma, lots of it.
posted by evilbeck at 1:28 AM on May 7, 2004

i was an art student, and while I understand that having pieces be "real" is important, sometimes you just need to work with appearances. Record a 60hz cycle and burn it to cd -- hide the playback well, loop it, you're done. Not as cool, assuredly, as having an actual ground hum, but a workable backup.
posted by fishfucker at 1:55 AM on May 7, 2004

evilbeck,

I'd borrow an electric guitar and amplifier. Select a single coil pickup (i.e., non humbucking) and play with the volume and tone. You could stick a bundle of extension cable near the pickup too. Just plug it into the wall and light a bulb or something. Guitar/amp rental is dirt cheap, at least when I've done it. As a bonus you usually rent really crufty old amplifiers which make their own 60 Hz hum.

I'm an EE but I'm generally not comfortable giving actual engineering advice out for liability reasons.
posted by substrate at 5:12 AM on May 7, 2004

i was going to post some comments, but on preview i think subsstrate's probably right, so i've deleted them. you sound like you don't have a clue and i wouldn't want to go anywhere near anything you'd made.

at least, step down to 12v using a "wall-wart" transformer, to keep the mains voltage away from the chair. splice in a thick cable if you want something that looks impressive connected to your switch. and make sure the circuit has a residual current circuit breaker (if not, you can buy them to plug in between wall socket and transformer).
posted by andrew cooke at 9:10 AM on May 7, 2004

I concur with andrew cooke -- it sounds like you don't have a clue. I would suggest INSIST you don't try to run any power through that switch at all. Hook up a regular light switch or something to power the little lamp and the buzzer off the wall AC... Don't bother with a transformer. As for the buzzing noise -- what about a small electric motor? You can hook some of these up to the AC.
posted by headless at 12:01 PM on May 7, 2004