Spectrasymbol HotPot analog bleed

Hello,

I'm using 3 SpectraSymbol HotPot rotary touch potentiometers to read values into the analog inputs on my Arduino - a pretty straightforward task. I have +5v and gnd from the Arduino running into a breadboard, and each of the three pots are powered and grounded from these strips in the breadboard. The middle pin on each HotPot goes to an individual Analog in port on the Arduino.

The problem is that touching one HotPot seems to affect them all... I ran them with the Critter and Guitari pocket piano software and noticed the effect sonically, then wrote a patch that just spit the analogread data out of the serial monitor. I tried this with both an Aruino NG and a Mega, and noticed the same result. What could I be missing? Can anyone suggest some troubleshooting tips to try to track down this issue? It seems like it must be something very simple I just can't seem to figure it out.

Thanks, /noah

Try putting a pull down resistor of about 100K on each analogue input. Also put a large capacitor (47uF) across the +5 and ground of the feed to the pots. Finally try a 0.1uF from the analogue input to ground.

wow, the combination of those three totally worked. thank you endlessly! I'd love to know the principle behind this - my knowledge of capacitor use is sorely lacking, but perhaps I need to do my own research...

thanks!

Glad it worked. :)

I'd love to know the principle behind this

Well for:- Also put a large capacitor (47uF) across the +5 and ground of the feed to the pots. http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

for a pull down resistor of about 100K on each analogue input This stops the analogue inputs floating and picking up noise and other disturbances. This happens because using that pot when nothing is being pressed there is no connection from the wiper to anything so the analogue inputs can float. The resistor is enough to ground them but not too small to affect the readings.

and finally:- a 0.1uF from the analogue input to ground will ensure that AC noise is shorted to ground.