Force Sensitive Resistors value fluctuation

CB1

Hi there,
I'm trying to move a project I built with and Arduino and PD onto a Bela mini.
All worked well when I was working with the Arduino. When I moved to the Bela mini I'm getting huge fluctuation on the sensor values coming from the force sensitive resistors. I could run the bela and the values could be 0.3 and then the next time 5 mins later 0.8. This makes it difficult to set the threshold value. Nothing has changed in the wiring.

I've added a pot to set the threshold manually each time I run the bela, but this will not be possible for the final application.

I'm powering the bela mini via USB from my Macbook air. I intend to switch to an external power supply after I finish prototyping.

Has anyone had any experience with this issue?

giuliomoro

Are you using 3.3v or 5v as a voltage reference for the sensors? Do you want yo share more details about your wiring?

CB1

I'm using the 5v. Here the Fritzling for my Arduino project. The wiring is identical.
alt text

giuliomoro

try using 3.3V instead. The 5V rail is very noisy on Bela and should not be used as a voltage reference. Also, you should always (also on Arduino) use series resistors for your LEDs, something like 220 or 330 ohm.