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  #1  
Old 02-09-2010, 10:23 AM
Driver8 Driver8 is offline
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"Touch" light switch turns itself on in the middle of the night - why?

We have one of those dimmer light switches that you tap to switch the light on and off and hold your finger on to dim or brighten the light. This controls the main overhead light in our bedroom.

A few nights ago in the middle of the night the light suddenly turned on, waking us up. I got up and turned it off without problems. The night before last it happened again!

I'm not 100% sure how these switches work. What could be causing this?
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  #2  
Old 02-09-2010, 10:36 AM
njtt njtt is offline
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A moth?
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  #3  
Old 02-09-2010, 10:45 AM
JerseyFrank JerseyFrank is offline
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Any chance it's an X-10 compatible switch?
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Old 02-09-2010, 11:28 AM
Driver8 Driver8 is offline
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Quote:
Originally Posted by njtt
A moth?
Maybe, although I haven't seen any.

Quote:
Originally Posted by JerseyFrank
Any chance it's an X-10 compatible switch?
What is that?
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  #5  
Old 02-09-2010, 11:32 AM
Finagle Finagle is offline
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I have one that does that too. I suspect it's sensitive to voltage fluctuations. This site seems to confirm that theory.
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  #6  
Old 02-09-2010, 11:37 AM
Harmonious Discord Harmonious Discord is offline
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Components in the electronics can be going bad.

Do your house walls bleed?
Have you stepped in something slimy?
In case of either the switch may be shorting out due to paranormal residue. Call 555-2368
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  #7  
Old 02-09-2010, 11:47 AM
Anaptyxis Anaptyxis is offline
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This happened to me in a place I used to live. Same scenario: dimmer switch controlling the overhead light fixture, the light suddenly coming on without anyone touching a switch. It turned out that there was a surge protector strip plugged in to the same circuit that was going bad. Once I unplugged that, and replaced the strip with a new one, it didn't happen again.

Disclaimers:
1) YMMV.
2) I am not an electrician.
3) Electricity can be dangerous.
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  #8  
Old 02-09-2010, 11:49 AM
BrotherCadfael BrotherCadfael is online now
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Your cats are planning on driving you crazy and making off with your inheritance.
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  #9  
Old 02-09-2010, 12:15 PM
CalMeacham CalMeacham is online now
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We always blame the ghost of the previous owner (she died the day we closed on the house, and had Alzheimer's. Our theory is that she doesn't know she's dead).


We've long suspect that voltage fluctuations have a hand in it, too. If you flick the wall switch that controls the outlet the lamps are plugged into, you can change the light level.
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  #10  
Old 02-09-2010, 06:51 PM
PapSett PapSett is offline
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Seriously... do you have a dog or a cat that can get to the lamp? My dad used to have a Sheltie that figured the touch lamp out and she used to drive us nuts, turning the light off and on... off and on... off and on...


She seemed quite proud of herself.
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  #11  
Old 02-09-2010, 07:56 PM
toofs toofs is offline
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I see dea...

Nevermind.
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  #12  
Old 02-10-2010, 09:52 AM
butler1850 butler1850 is offline
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Quote:
Originally Posted by Harmonious Discord View Post

Do your house walls bleed?
Have you stepped in something slimy?
In case of either the switch may be shorting out due to paranormal residue. Call 555-2368
Shhhh... those are the NEXT steps! You're spoiling the experience for them!

Ghosts... or voltage variations... or you need a new switch.
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  #13  
Old 02-10-2010, 02:41 PM
Ann Hedonia Ann Hedonia is offline
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I have a lit magnifying mirror with a touch switch and sometimes it will go on sponanteously if the cord on my phone charger is touching ANY part of the lamp (not just touch part, it will trigger if the two cords are touching).

They work by detecting capacitance changes -- nothing happens if I hit the base of my lamp with the sole of my foot while wearing tennis shoes. I'm not sure what could cause those changes spontaneously though.
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  #14  
Old 02-10-2010, 03:48 PM
Driver8 Driver8 is offline
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No pets in the house, although the switch would be too high anyway. Thanks for all the answers so far. I think the most likely cause is voltage spikes - I can't see what else it could be.

The previous owner is alive and well and seemingly not distressed by the dead, so I am suspecting natural causes.
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  #15  
Old 02-11-2010, 06:32 AM
Terry Kennedy Terry Kennedy is offline
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Quote:
Originally Posted by Driver8 View Post
We have one of those dimmer light switches that you tap to switch the light on and off and hold your finger on to dim or brighten the light. This controls the main overhead light in our bedroom.

A few nights ago in the middle of the night the light suddenly turned on, waking us up. I got up and turned it off without problems. The night before last it happened again!

I'm not 100% sure how these switches work. What could be causing this?
Those normally rely on capacitance to detect touch. It is actually a tuned oscillator that is detuned by body capacitance.

The only time I've seen them cycle by themselves is when there is very high humidity - the light will continuously cycle up and down in brightness. But it is possible for transient noise on the power line to trigger it.

If this happens to be an old-style "Sensitron" unit (pre X10), it will have a cover plate with a large oval touch surface and a somewhat hidden switch on the bottom edge of the cover plate. If you pop the cover plate off, you'll see a copper spring in the middle of the actual dimmer which contacts the cover. Check for dust / cobwebs / etc. between the spring and the surrounding metal area.
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  #16  
Old 02-11-2010, 07:01 PM
figure9 figure9 is offline
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Quote:
If you pop the cover plate off, you'll see a copper spring in the middle of the actual dimmer which contacts the cover. Check for dust / cobwebs / etc. between the spring and the surrounding metal area.
But be sure to unplug it first!!!
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  #17  
Old 02-11-2010, 07:48 PM
Terry Kennedy Terry Kennedy is offline
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Quote:
Originally Posted by figure9 View Post
But be sure to unplug it first!!!
Good general advice. In the case of the particular Sensitron unit I'm talking about, the cover is a snap-on decorative cover which just contains the touchpad surface. The actual guts of the are behind another aluminum panel, with the only protruding part being the sense spring.
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  #18  
Old 02-11-2010, 07:54 PM
Arnold Winkelried Arnold Winkelried is offline
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This is very interesting to read for me, because I have a similar situation:
a unit that controls a light and also the ceiling fan in the same fixture. The unit has 4 buttons: 3 ceiling fan controls and one light control.
There are three buttons for the ceiling fan: high, medium, low.
For the light switch, you can either press the light button to turn on/off, or else you can keep your finger on the light button to have it go from dim to bright and vice-versa.

Sometimes I will be sitting in the room and the ceiling fan will come on by itself. I have the same system in two rooms and it only seems to happen in one room, and only in the summer. This is the room that gets the warmest because of the way the windows face. Could it also be because of voltage fluctuations?
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  #19  
Old 02-11-2010, 08:14 PM
Driver8 Driver8 is offline
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Quote:
Originally Posted by Arnold Winkelried View Post
For the light switch, you can either press the light button to turn on/off, or else you can keep your finger on the light button to have it go from dim to bright and vice-versa.
This is how my switch works exactly. When it turns itself on it goes straight on and stays there - the brightness isn't adjusted in any way.
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  #20  
Old 02-12-2010, 01:33 PM
constanze constanze is offline
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The reason has already been given - fluctuations in the power line - , I just wanted to add that this reason was told to me by an employee (IKEA) in the lamp shop who sells touch lamps, and has heard from customers in some areas (where apparently the power varies more) that the lights go on during the night, and how puzzled they were.
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  #21  
Old 02-12-2010, 01:59 PM
Anaamika Anaamika is offline
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Can I piggyback my question on to this one? We have a battery operated light that you have to touch two points on to make it work, basically, completing the circuit.

The other day it was in the bathroom as I was showering. When I came out, the room had filled up with steam. My eyes were drawn to it and without touching it, suddenly it turned on.

Did the steam really complete the circuit and turn it on?
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  #22  
Old 02-12-2010, 02:07 PM
Magiver Magiver is offline
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Quote:
Originally Posted by Anaamika View Post
Can I piggyback my question on to this one? We have a battery operated light that you have to touch two points on to make it work, basically, completing the circuit.

The other day it was in the bathroom as I was showering. When I came out, the room had filled up with steam. My eyes were drawn to it and without touching it, suddenly it turned on.

Did the steam really complete the circuit and turn it on?
The steam, no. The condensation from the steam, yes.
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  #23  
Old 02-12-2010, 02:09 PM
Anaamika Anaamika is offline
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Originally Posted by Magiver View Post
The steam, no. The condensation from the steam, yes.
Yes, that is what I meant, my apologies. Neat. Thanks!
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  #24  
Old 02-12-2010, 02:24 PM
constanze constanze is offline
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Quote:
Originally Posted by Magiver View Post
The steam, no. The condensation from the steam, yes.
Huh - How? Condensed water should be 100% pure, yes? So nothing to carry electricity, yes? So how could contact be closed?

I mean, I watched a video from PC-World where they spilled a whole mug of distilled water into a running computer, without any reaction at all (don't try with normal water; they wanted to prove how safe a water-operated cooling system is even if it leaks).

Last edited by constanze; 02-12-2010 at 02:25 PM..
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  #25  
Old 02-12-2010, 06:40 PM
Fridgemagnet Fridgemagnet is offline
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I had this happen on a touchswitch/dimmer; it turned out to be a failing joint on the circuitboard that was easily fixed by re-soldering. But there are a lot of things that could cause the same symptoms, usually leading to noise-induced glitches in the control circuitry. The touchswitch could be fine, but a loose wire making intermittent connection would generate enough noise to get through, as would someone TIG welding in the vicinity, say.

Usual safety precautions for mains etc., don't poke around if you're not familiar with the procedures.

On an aside, I'm not sure I want to splash distilled water inside my PC. Even in its ultra-pure state it's not a perfect insulator, (cite) once it gets onto a grubby circuitboard it stops being pure pretty quickly. Once it dries out it will leave behind a legacy of metal oxides on the solder joints that will grow with time and eventually eat through the circuitboard tracks. I suspect the boards in the PC World ad were conformally coated, possibly the various connectors sealed too.

Last edited by Fridgemagnet; 02-12-2010 at 06:42 PM.. Reason: link error
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  #26  
Old 02-12-2010, 08:05 PM
Apex Rogers Apex Rogers is offline
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Originally Posted by constanze View Post
Huh - How? Condensed water should be 100% pure, yes? So nothing to carry electricity, yes? So how could contact be closed?
There are particles in the air and also on the surface of the light switch, be it oil, dead skin cells, sweat residue, grime, etc. I don't think you can assume that the condensation is equivalent to distilled water.
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  #27  
Old 02-13-2010, 12:32 AM
Cheshire Human Cheshire Human is offline
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I do electronics, and have built a touch switch, my own design, not copying someone else's. It's minor voltage spikes, the same as your surge protector saves your computer from. Since all components have tolerance + or -, you get some more sensitive than others. The less sensitive, the sharper the spike it takes to turn on. Plug your lamp into your computer's power strip, and it will never happen, til the power strip goes bad.
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  #28  
Old 02-13-2010, 12:29 PM
constanze constanze is offline
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Quote:
Originally Posted by Fridgemagnet View Post
On an aside, I'm not sure I want to splash distilled water inside my PC. Even in its ultra-pure state it's not a perfect insulator, (cite) once it gets onto a grubby circuitboard it stops being pure pretty quickly. Once it dries out it will leave behind a legacy of metal oxides on the solder joints that will grow with time and eventually eat through the circuitboard tracks. I suspect the boards in the PC World ad were conformally coated, possibly the various connectors sealed too.
No, it wasn't an ad, it was PC-Welt (PC-World Germany sister) TV. That is, one of the journalists made the experiment and filmed it and put the movie on the monthly CD/DVD that's added to the magazine. Don't know where the disc it's on currently is, though.

The journalist claimed that it was an ordinary PC, not treated, and the same distilled water that is used in the watercooling. Even if the modern PCs sold with watercooling systems on board are specially treated, PC-Welt also advised readers to change existing PCs, since watercooling would be more efficient than the normal fan (esp. for gamers and DIY guys who overclock their processor and have high loads and thus a lot of heat). Though maybe one of the prepatory steps would be cleaning and coating the main board - I don't remember the details.
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  #29  
Old 02-14-2010, 04:58 PM
Driver8 Driver8 is offline
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Voltage spikes it is then. I've experienced it even worse since posting here - basically if I switch the light off a second later it switches itself on again and it seems to do this all the time now.

Interestingly it has gotten worse rapidly, and worked perfectly for as long as we've been in the house before a week or so ago. There is a tiny mechanical switch as part of the unit which I have now just switched off - we'll use bedside lamps instead of the overhead from now on. This is a light switch in the wall, not something that can be plugged in anywhere else.
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  #30  
Old 02-15-2010, 12:53 AM
Cheshire Human Cheshire Human is offline
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That's the thing going bad, then, if it's getting more frequent. It needs to be replaced.
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  #31  
Old 02-15-2010, 02:56 PM
Fridgemagnet Fridgemagnet is offline
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What Cheshire Human just said. From the symptoms update I'd definitely suspect an intermittent contact, either from a poor wiring connection or a failing solder joint. The risk of a fire breaking out from the arcing is small, but best to be safe.

Do post the autopsy reports. Check for signs of burning around the screw terminals and the solder joints on the larger components.
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