Pre-made No-Touch CapacitiveSensor

I need some help in finding a sensor. I want something that will sense when a human body is nearby (in my case when I am sitting on a chair).

I don't need any fancy data reported to the Arduino - pressure, weight, distance, etc - just yes or no if my rear end is within a few inches.

The functions described in the Capacitive Library sound like they fit the bill exactly, but I am hoping to find a pre-made sensor for two reasons:

  • This is my first Arduino project and I would rather not get into the wiring, soldering, etc quite yet. I also don't have the soldering equipment, not to mention the fact that components needed usually have to be purchased in quantity and I only need one of each.
  • I am hoping to write-up a tutorial and I'd like to make it accessible to others like me who can't wire things together.

I don't mind a little cost (especially if it works straightforwardly), as commercially available alternatives to the device I want to build cost upwards of $100 USD.

Don't worry about buying "in quantity". You can order quite small volumes from vendors like RS-Online (at least in my locality, and it includes free delivery) and left-over components you will find a use for sooner or later.

It's for you probably simpler to build your own sensor, as a capacitive sensor is basically a metal plate (e.g. alu foil, glue that on your seat under the lining) and a resistor. This way it'll fit in your seat easily. Not likely you can find a commercial sensor that can easily be built into your chair.

Thanks. I guess I'll have to dive in. :confused: I appreciate you recommending RS-Online. That gave me some place to start.

If I am following the CapSense reference correctly, I need a 10 MΩ resistor and a 200 pF capacitor for my specific application. But RS-Online seems to stock various 10 MΩ resistors with different wattage ratings and various 200 pF capacitors with different tolerance ratings. Any idea what I'd need for this project?

Also, any thoughts on whether copper foil would work better than aluminum, or are they both about as good?

For resistor, any power rating will do as the actual amount of power dissipated is very close to zero.

Capacitor tolerance doesn’t matter too much for this application; the 200 pF value is flexible in itself. A regular ceramic cap should do just fine.

You can also look at ADCtouch instead of Capsense.