The QT100 touch sensor

[Electronics4you]

Hi There,

Does anyone know if the dielectric material used on top of the electrode pattern are supposed to touch this, though it's a near proximity sensor?

 

[audioguru]

Please provide a link to the datasheet for the QT100 so we can see what it is.

 

[RadioRon]

This appears to simply be like an elaborate capacitance meter, so if you cover the electrode with a dielectric, it will still work. It is probably best of you don't use a thick dielectric or you will reduce the change in capacitance when the finger comes close or touches. For this reason, you probably do want the dielectric to touch rather than float above the electrode. I'm wondering why you will cover the electrode with a dielectric at all. This is like putting another capacitor in series which reduces the overall sensitivity doesn't it?

 

[Russlk]

I used the q100 once, as I recall, I only had to be within an inch of the sensor (air dielectric). If you used a dielectric with a constant of 3 or 4, I think the distance might increase.

 

[Electronics4you]

Using air as a dielectric isn't good, while having several touch sensors in a row. First of all the dielectric will decrease the distance and second a dielectric material is better than touching the PCB alone.

 

[jjj]

I thought of using this QT100 touch switch **broken link removed**
for a musical keyboard to switch the Synth's switches. Maybe it's too expensive?
What about a simple one transistor circuit with 1M impedance at the input?
Any constructive criticism/ suggestions are of course welcome.