Detect capacitance change on a wire when it comes into contact with a second wire

Michael @ Afineol

Initially I thought resistance, but I think capacitance. I was looking at the Capacitive Touch Sensor from SparkFun, but this is for the human body.

I will have a 3' 18 gauge wire attached to a stainless steel plate that is less than 1 mm thick and 4" x 4". I need to detect a stainless steel rod that is 1/8 diameter 1' long striking the plate at the tip.

Any sample circuit and spin code would be appreciated.

kwinn

Can you post a diagram of this? what is the wire material, gauge or thickness? Is the other metal plate connected to anything? A description of what you are trying to do would also help.

Peter Jakacki

Michael @ Afineol wrote: »

It has been a long time since I did anything with my Prop. I was hoping someone could help me with the circuit and some sample code.

What I want to do is have a metal plate that is attached to a wire that is connected to my Prop. When it comes into contact with another metal plate, not connected to my Prop, I want to be able to detect the change in resistance. Or I think that is what I want to detect. Any suggestions would be appreciated.

Mike

You can only measure resistance when it's part of the measuring circuit and what you have is a piece of wire going off to a plate which may contact another plate which does not connect to anything else, that is not a circuit.

It may be possible to measure the capacitive loading affecting the rise time of a resistively coupled pulse on the line, the pulse is sent from one pin and another measures its rise time. But unfortunately I think that you may have a lot of noise issues. The best bet is to have the remote metal plate as part of a circuit.