ECN Electrical Forum
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How does a "touch lamp" work?

GFI principal ???? now i'm gonna have to disect one of those little boogers..!

Before Scott can give us the right answer, (I mean that in a good way) I'm gonna go out on a limb and say that it has something to do with sensing the slight voltage potential difference between your body and ground...

Nope.. scratch that they seem to work even when my body is "bonded" to neutral, and I touch the lamp.

Is it similar to the 60hz hum you hear when you touch the tip of a guitar cord that is plugged in to an amp? (I realize the hum is the AC cycle frequency a slightly flat B-flat.)

I think it has something to do with capacitance?

Yes? / No?

Bill

the bodys resistance in to ground completes a circuit SOMEHOW

I found some info on this at another site:
http://www.madsci.org/posts/archives/may98/893276774.Eg.r.html

The Main site may also have some interesting things:
http://www.madsci.org/

Hi all,

Well, simply the sensing circuitry works through a large change in the Capacitive Charged Field on the metallic lamp it's self.

When something connects to the metallic fixture, which is a Capacitive type of connection - and has a higher level of "Storage" than the existing one [the fixture, the Dielectric Air, and some other conductor - plus possibly the earth ground too], then the circuit's overall charge gets changed.

The thing that the sensing circuit is looking for is an alternating current close to the frequency that is used to run the lamp it's self.
When it finds a high level of 60 Hz AC in the sensing circuit, it interprets this as a "Request" to change the state of the output. This connected to a 'Flip-Flop" type of gate [Binary Switches], will either turn on the load from an Off state - or the opposite.

Any body that exibits a Capacitive effect will work. I have found that touch dimmer type lamps will run the dimming control over and over when the fixture is set on a surface that is still damp from using a liquid cleaning solution on it [in this case - Windex].

Scott SET

so Scott;
.......
in the previous volt-tic thread we had a similar moisture barrier like the windex that served as a resivior for electrons or capactitance ?
I take it that I, as a capacitor, am assuming a nil amount of electrons to function said lamp???