Capacitive touch on metal door

For a project I have been working on, I want to sense if the door handle is being touched. I planned to do this by using the Capacitive Sensing Library, with a wire going to the door handle. However, I realized that the door is also metal, which makes my values largely increase so it does not react to a hand on the knob. Is there anything I can do to get my desired effect, where the Arduino can detect if a hand is touching the knob?

It is going to take a lot more than that.

Back in 2007 I attended a seminar at a Cypress semiconductor distributor who were selling their new Pcos processor with a bit of FPGA on the input pins. Their prime application of this was to be able to make a good capacitive touch sensor with one application they said was for car doors.

It was complex as the handle had to be electrically isolated from the body. Then the processor had to be mounted in the door so it was close to the handle with the handle being the sense electrode and the door the ground shield. Then the wiring to the rest of the car was passed to the main control processor through the route the wires that carried the window opening controls took.

An Arduino touch sensor library is not a very good touch sensor, it is more of a demonstration thing rather than a serious sensor. So I would suggest you get a proper sensor chip, and not the cheap 121 chip either.

Only then do you stand a chance, but it will not be an easy project to get right.

What is the "121"?

What about the TTP223?

The MPR121 capacitive touch sensor.