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Thursday, November 08, 2007

frankenstein light switch

[click photo for gallery]

So for a little home-improvement hacking this time, I installed a sweet knife switch to turn on/off the ikea lights i put up in my kitchen.

You can use a switch that has bare contacts like a knife switch as long as the power that is running through the circuit is SAFE - 12 volts or so - and even then, don't short the contacts with a fork or what have you, because it will still make a big spark and scare the children.

Anyhow if you click the button above for the photo gallery, or watch the video below you'll see how I did it - though I didn't explain too clearly exactly how the switch is wired up - all you gotta do is make it so that the switch connects and disconnects the power from the lights. And if you're not familiar enough to do that, DONT TRY, because you probably also won't know if the power you're using is 12 volts or not :P

By the way, did I mention how you should NOT use this kind of switch on anything but a safe voltage like 12 volts? TWELVE VOLTS OR LESS PLEASE.

[ click over there to leave a comment ---> ]
5 pillowblog: frankenstein light switch [click photo for gallery] So for a little home-improvement hacking this time, I installed a sweet knife switch to turn on/off the ikea li...


Anonymous said...


Nix said...

Baby, what are we gonna do when the children come? are you trying to harm them? what is this nonsense?

James said...

is right above a sink the best place to do that? even with 12Volts?

Anonymous said...

12V is harmless. Unless the current gets too high and something overheats and ignites, but that's true for any voltage.

The same approach can be used for controlling 115/230V equipment; the 12V segment (optionally 5V) is then used to control relays that do the high voltage switching.

An even more secure alternative of the former is using solid-state relays with a built-in optocoupler. The current through the exposed switches then can be limited to few milliamps by a series resistor, as then it only drives the LED in the SSR. Locate the resistor as close to the power supply as reasonable, as the part before it will react more catastrophically to an eventual short circuit.

David Cook said...

Whoa! Hold on! 12V can definitely kill you.

Ever hear of people being electrocuted from a 12V automotive battery? Yup. Especially with moist hands. This is in your kitchen above your sink?

I know this looks cool. But, please, for the sake of yourself and your family -- unplug this.

There is a safe way to use the cool knife switch. Accept the advice of the person who suggested an optical relay with a series resistor to limit control current. That way, the switch has almost no power flowing through it, and the relay actually connects the power source to the lights.

John said...

@david cook:
You are right that 12 volts can kill someone - but only at high amperage. Voltage is irrelevant - .5 volts could kill someone and 100,000 volts could not. It is amperage that is dangerous, and im guessing this wall wart puts out a few hundred milliamps or maybe an amp or two, which is harmless.

Andrew said...

@david cook, john:

12v is pretty harmless. The only times I've heard about people getting shocked from a 12v battery are when a ring on their finger and a wrench complete a circuit. You might short the circuit and blow a fuse, but harm to you is unlikely. Of course, electrons are tricky beasts, so protecting the switch from moisture and errant tongues might not be a bad idea.


really, it doesn't take much current to kill you. a few milliamps through the chest is probably enough.

Anonymous said...

Right. A car battery can kill, when you consider 12volts at 100+ amps. Not 12v at 2amps across one hand. Even with two hands, the body produces enough resistance to not allow the ciruit to complete through the heart. Ever use one of those shocker pens or games? Those produce atleast 12v at 1amp.

Anonymous said...

Safety aside, I am wondering why the switch on these (I bought a set myself) is located so close to the tranformer. It makes it difficult to use (I have them in my bedroom as reading lights). Eventually I think I'll install a deicated switched outlet for these cool-looking lights. I concealed my wires w/ some wire molding I bought at Lowes (adding about $12 to the $14 at IKEA)

Miko Fulla said...

"You wouldn't want mainline power here. That would be bad".
Haha classic quote.

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