Touch Lamp Technology

[petemoore]

  Seems like a logical thing to become interested in here...
  Touch the lamp and it goes from state '0' to state '1', touched again it bumps to stage 2, all four stages cycle 1,2,3,0...'zero' being the 'off' state.
  Just a two state touch 'thing' would be interesting to investigate, the chips don't seem to last very long when a 120vac supply is used [1 x 3leg chip, 1 x 8pin chip, 7 resistors, a few carbon caps]....2'' square board....looks simple enough !
  Anyone play around with or find a 'touch' circuit that operated @9VDC [or 'low', say 18vdc] ?

[Taylor]

What are you thinking of using this for? Is this to replace the on/off stomp, so you just tap the box anywhere and it cycles on/off?

[space_ryerson]

I've been doing some research into capacitive touch chips, but haven't gotten as far as to build anything yet. I've recently read these two links which I found informative:

one
two

The QT-100 chip mentioned in the second link works between 2V and 5V

[WLS]

You could use it for effects.

The only problem is you may have to kick the box several times to get the effect you would desire.

Or if while playing you accidently touch it. Well...

Interesting Idea Though!



Bill


'

[juse]

I thought about somehow working this into a pedal a few years ago, but then I noticed that my touch lamp would sometimes come on by itself - especially on humid days.

[Taylor]

I thought about somehow working this into a pedal a few years ago, but then I noticed that my touch lamp would sometimes come on by itself - especially on humid days.

Well, we could all use a little indeterminacy in our music, don't you think?

[juse]

You're right, Taylor..... on second thought it might work good with a burst box.

[trendyironicname]

wouldn't you have to play barefoot to get it engaged/disengaged?

[doitle]

What about using the strings as your antennae? The effect modulates itself based on how you are touching the strings. That sounds neat to me. Don't know how possible or feasible that is but it's an idea.

[Paul Marossy]

Those touch lamps won't work unless you touch them with your bare hand...

[ayayay!]

You could use your 3rd leg. 

[Paul Marossy]

FYI: Here's a page on the methods used on touch lamps: http://science.howstuffworks.com/question42.htm
Touch lamps work based on the capacitance of the human body, which is what I would have guessed...

[earthtonesaudio]

No touchy?  No problem:
Theremin->pitch to voltage->comparator->switching circuit.

Just get close enough.

Or... a bazillion other ways.

[bside2234]

Just get some flesh and glue it to the bottom of your shoe 
or cut a hole in your shoe under the big toe, don't wear socks and pop your toe out the hole. See you could sell specialized shoes with the pedal!

[The Tone God]

Most touch lamps use an IC series that came out awhile back which have most of the required control circuitry built into it and runs off the AC line. I forget the series name right now but they work by sensing the body picking up local AC noise. Not a good way to sense a body precence for this function.

I'm pretty sure if you do a search of my history I have posts talking about touch control and the pro and cons of various methods.

Andrew

[space_ryerson]

Capacitive touch doesn't necessarily require you to touch it with your bare flesh... just look at an iPod wheel!

[The Tone God]

It can be done but there alot of details. Mainly how to do it so it doesn't create noise in the audio and the design the sensing surface.

Andrew

[Taylor]

I'm still not sure what the point of this is. If it's to replace the 3PDT, for f's sake, then cool. I'm all for having fun with no "practical" purpose.

If the idea is to use capacitance like a theremin to control some parameter, the "earth and space interface" is a good place to look.

[space_ryerson]

It can be done but there alot of details. Mainly how to do it so it doesn't create noise in the audio and the design the sensing surface.

Andrew

Is the noise due to the PWM signal?

[The Tone God]

Is the noise due to the PWM signal?

It depends on the technology being used. In the case of the lamp its the line AC. There are a number of way to sense a body presence. I think somewhere I have a post where I cover the more popular ones. AFAIK no touch sensing technique uses PWM. Many do use a clock source of some sort. Most of the "theremin" circuits use the body's capacitance to alter the frequency of the clock. This can be very tricky which I also discuss in some previous posts and why I don't like this system.

Andrew