# Capacitive touch button panel

#### >Chris<

Joined Oct 16, 2008
17
Hi guys,
I want to control some LEDs in my house and was thinking about doing that with a Plexiglass panel that has capacitive touch buttons.

I was thinking of having around 6 buttons that are lit by LEDs and some fairly thin plexiglass. I would also like to have this powered by 12V.
I checked out some circuit designs like this one http://www.discovercircuits.com/PDF-FILES/12vexc1.pdf but I think for circuits like that, the dielectric of the button has to be touched directly and can't be covered. I'm not totally sure on that though.

I also looked at the Atmel QT series like the 42QT1060 which seems to incorporate the functions I am looking for. I don't know how much work it is to set one up though.

Does anyone have experience with this? Your help is much appreciated!

Thanks guys!

#### KMoffett

Joined Dec 19, 2007
2,918
Looks like the 42QT1060 is obsolete. You might look at microcontrollers that contain this function...like PICs or PICAXEs.

Ken

#### eeabe

Joined Nov 30, 2013
59
I was recently involved in a product development where we used an ST-Micro MCU. It was our first cap sense and it worked fine, although the sensitivity is highly dependent on the physical assembly and any air gaps, etc. They provide a lot of good documentation, as does Atmel I'm sure. If you're comfortable with microcontrollers in general, I'd say the biggest part of the project will be reading up on cap sense and laying out the PCB with the sensing locations. Overall, not too difficult, and pretty neat when it's done.

#### elec_mech

Joined Nov 12, 2008
1,500
You might look at microcontrollers that contain this function...like PICs or PICAXEs.
+1. PICAXE has a nice simple way to implement a capacitive sensor. I used one to make a start switch for a timed night light from a piece of brass. The most challenging thing is find material that the sensor can still detect through. I attempted to put this piece of brass in one of those ABS boxes RadioShack sells and I could never get it to work. I even thinned the material as much as possible, but no dice. Ended up spraying the brass with clear coating and just let the user touch the brass. I imagine Plexiglas would work much better.

Now other products may do a much better job of detecting capacitance, but be prepared to spend a lot of time reading application notes. If you want to dive in and just make something, give the PICAXE a shot. It's programmed in BASIC, the chips are relatively inexpensive, the software is free, and all you need is the uC itself and a cheap USB-to-TTL adapter and an inverter IC like the 74HC14 (all for under $10 USD). Alternately you can buy a dedicated programming cable and demo board for$30 - \$50.