capacitive touch sense

yes indeed thanks for that , i am near lots of electronic units. the plate must just be too good an antenna and is picking everything up.(i do need to use this plate) however There may still be hope as there is still a slight change in brightness when I touch the plate, so i could send that signal (which powers the led) into the computer via the arduino analog input and software max msp ...in there i can set thresholds (gates), for the progam to listen out for slight changes above a certain threshold (for when i touch the plate). then the software could output 5v so that i can trigger a relay for example. the only problem then is that i do lose two channels on my arduino micro controller (an input and an output)

i may give it a go. i'll just have to see if i can afford to use the 2x logic ports and if i do find the time i'll post here if i succeed. : )

Thanks for posting that circuit and helping me realise it is the environment/plate causing the problems.

peace

You can turn an input line of a micro into a very sensitive electrostatic detector by adding a 100p and charging the cap for 1uS then waiting for 20mS and seeing if the capacitor is discharged.
This eliminates the effect of stray charges produced by electromagnetic radiation and static build-up from paper and plastic products.

colin55 said:

Nearly all capacitive touch sensors pick up mains hum.

Click to expand...

That would be unreliable and probably what the original poster observed. Commercial touch sensor buttons use pulling of frequency on an oscillator circuit.

http://www.discovercircuits.com/C/capacitance-sw.htm

Is this at all helpful? YouTube - Capacitive Touch Sensor: Learn Electronics with a Spooky Halloween Project!