Soda can turns on lamp

[gigi]

So I've got one of those lamps that when you touch any of the metal on it, it turns on and off. It's not a tap light where the lamp moves and turns on and off, it's just a touch that does it.

Previously, only touching it with my hand (or presumably another area of skin but I haven't been that adventurous) would work, and not any other object. But last night, I by chance touched the metal part with the base of my aluminum soda can. It activated the light!

I knew I would have to ask about this so I did some very casual experimenting. It seemed to be toward the base that did it, where there is the ridge of aluminum. It worked with a little bit of soda in it; I drank the rest of it to try an empty can, which also worked but I can't swear there wasn't still a little bit of soda left.

It was around 70 degrees in there, so it's not like the soda was as warm as a human. I even thought of backwash but I don't think there was much at all, or enough to warm up the can. It didn't feel very warm and I hadn't been holding the can in that area.

What could it be??

[dasgupta]

From what I recall, touch sensitive lamps work on the human body's capacitance. Since the metal can provided a direct path from you to the base (it was a good conductor), this still works. From my experiments playing with my grandmother's lamp, many other conductive metals also work.

See also HowStuffWork's explanation.

Of course, I could be remembering wrong, but hopefully an electrical engineer will be around shortly.

[CalMeacham]

When I read the thread title I thought either:

1.) You Soda Can and Lamp are romantically involved?

or


2.) Who knew Soda Cans could be so viscious?




Seriously, though, I believe those lamps work by changes in capacitance. I'd think the touch of any metal object would do it, especially if grounded. Heck, ours turn on all the time by themselves with nothing touching them. We blame the ghost of the original owner of our house.

[gigi]

Originally Posted by CalMeacham

2.) Who knew Soda Cans could be so viscious?

Especially when soda is not very viscous at all.

Thanks! I should have known to check How Things Work, even though I don't quite understand what they're talking about.

[Stealth Potato]

Did you try touching the can to the switch while wearing gloves, or holding it with non-conductive tongs? I'll bet it wouldn't work then.

[gigi]

Originally Posted by Stealth Potato

Did you try touching the can to the switch while wearing gloves, or holding it with non-conductive tongs? I'll bet it wouldn't work then.

Hmm. I sense an experimental evening coming on. Yes, this is as exciting as my evenings get, when "rubbing my lamp" isn't even a euphemism for anything.


I love your user name!

[GargoyleWB]

Once had a cat whose favorite path across the room was over an end-table with one of these lamps. It would usually circle around the lamp once or twice, flicking it on and off as it brushed against it, before continuing on its way.

[Stealth Potato]

Originally Posted by gigi

I love your user name!

Heh, thanks. Don't ask me how I came up with it; I don't remember. Obviously something to do with extra-quiet potatoes.