MPR121 Capacitive Electrodes - Erratic Behaviour

Hello,

I am having some difficulties with the sensitivity of the capacitive electrodes of the MPR121 touch sensor controller when changing power supply.

I am currently using a power supply that outputs 9V, 2500mA & everything works fine (using the default settings in MPR121.h), but as soon as I switch power supply to one that outputs 9V, 1000mA the electrodes start behaving erratically. I haven't changed any of the code, so I'm assuming it has to do with the amperage of the power supply, but why should that affect it?

Has anyone else encountered this problem?

Cheers,

Lee

i would guess that the new PSU isnt just weaker,
but: it also has higher ripple noise...

maybe a low pass helps?
or a 1mF capacitor across the new PSU?

+9V ----- LLLLL -------- Vout
|
===== C
|
GND----- LLLLL -------- GND'


2nd theory:
maybe the new PSU is not isolated from mains ground? XD

If both supplies are going through the on-board 5V regulator I would have thought ripple won't make any difference. Its likely the difference is noise that one of the PSU's is injecting onto the mains wiring that is capacitively picked up by the touch sensor - perhaps one PSU has its operating frequency close to the capacitive touch sensor?