Go Down

Topic: Capacitive Touch (Read 9157 times) previous topic - next topic

galkno3

Hey guys. I am currently working on a coffee table with glass surface. I will be putting an RGB LED strip under the surface and would like to control / change the colors using an Arduino instead of the IR remote it came with. So far, no problem. However, I would like to use the glass surface of the table itself as a capacitive touch sensor. I.e. areas on the table which when 'touched' change the RGB LED to a particular/specific color. Don't know if any of you have ever heard of RetroTouch light switches but I would like to do a similar switch were a glass surface (the table surface itself) is changed into a capacitive sensor in a particular area. The picture below is the RetroTouch light switch.



You may ask "why don't you just buy one of these switches and integrate it with your led strip?". That is because I would like to keep the table surface as one whole piece of glass.

Thanks!

pylon


galkno3

Had seen the video demo during my research and appeared that it will not be suitable for me since I will be covering the copper sheet with thick glass not realizing that changing the resistor changes the sensitivity! Sheesh! Shame on me. Thanks!

galkno3

Does a hotspot potentiometer work from under a glass? Or should I cut copper in form of a circle?

Grumpy_Mike

Quote
Does a hotspot potentiometer work from under a glass?

No.

Quote
Or should I cut copper in form of a circle?

You can if you want but it will not help you any.

galkno3

After looking on the web for some long hours, found out what you just said! So thanks for that info! I'm going to experiment with putting different/isolated pieces of copper plates in form of a circle each having their own resistor and such to act as a different 'button' so to say but appear as a single potentiometer when under a glass. I'm hoping it works! *fingers crossed*

Riva

Don't PM me for help as I will ignore it.

Magician

Quote
a circle each having their own resistor
Can't understand how resistor could help to read which of the plates the closest to finger? With glass above?
I'd suggest , to form a circle with just 3 plates, 120 degree each with small spacing in between.  Than you use capacitance sensoring code (theremin, probably would be the best) to measure distances to the finger, only you need "scan" one plate at a time, rotating "vector" fast enough, at least 10 Hz or so.  In software, you will process not the absolute C values, rather variation (differential C1 - C2, C2 - C3, C3 - C1), to get information which direction finger rotating. Basically create "capacitive encoder" , don't know if such device already exist or I just invent it -);.

galkno3

#8
Jun 19, 2012, 04:27 pm Last Edit: Jun 19, 2012, 04:30 pm by galkno3 Reason: 1
The circle will be definite touch i.e. triggering occurs only by touching the glass itself and not when in close proximity. That is why a 1MOhm resistor will be used (as suggested by the CapSense library's author - Paul).

Can't I just put different pieces of copper in the form of a circle and each one would act as a different button? (as shown in the crappy attachment where different plates form a circle [a hexagon rather but that's a quick version] each connected to a different resistor).

It's basically http://www.youtube.com/watch?v=BHQPqQ_5ulc&feature=related but instead of 3 strips next to each other, as I said, pieces of copper (separate) set in form of a circle. What do you think?

UPDATE: I had found this video couple of days ago and this is exactly what I'm after except that glass will be on top rather than cardboard. http://www.youtube.com/watch?v=rtzeizcHEYo&feature=related

Grumpy_Mike


galkno3

That looks like exactly what I'm after although all those specs are a bit beyond me lol.

Go Up