Hi,

I am a bit stuck here. I have tried to find an IC or a circuit to have something to start with. The target is to build a capacitive obstacle detector that is based on an elector plate on top of the device itself. When a human comes close, the capacitance change is detected and digital circuit takes care of the rest. I could just design a capacitance measurement circuit from scratch, but maybe there is something already available...

br,

A

 

A multi stage Darlington transistor configuration could work. Using a long wire as a floating base, I easily coupled my body to the circuit by coming near with 3 stages of 2n3904 transistors. I have an idea in the hopper to make a loop in a doorway so when I walk through a device is triggered.

 

Have a look at a theremin circuit. It uses proximity to change the frequency of an oscillator and is quite sensitive you would need to add some form of detector so a changed frequency gives you your output.

 

There is a new cheap FMCW-Radar-Board available ..............

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