Midi Controller Varying Voltage issue

Hey Everyone,

I’ve built a couple prototypes of a custom midi/synth controller I designed, but I’m having a strange issue with it that is hard to describe. It has 30 pots (connected by multiplexers), a few multi-position switches(shift registers), and then some buttons. One of my prototypes works totally great. But the other sends out readings constantly even when I’m not touching it. And what values it sends out constantly and how fast it’s changing depending on the position the switches are set. So for example when my second multi-switch is in position 5 then my 10th potentiometer will be sending out it’s value hovering up and down constantly and quickly. But if the multi-switch is set to position 0 then the 10th potentiometer then sends out no changes. But sometimes it’s not the 10th potentiometer but the 16th instead.

Now when you take values from the analogRead in the arduino, they do vary sometimes, but my code doesn’t send out values unless a more significant change in voltage occurs.

So basically I think it’s a soldering issue, however when I use the multimeter it seems all connections are fine. So I’m not even sure. Why would the voltage vary slightly for certain pots and not others? Why does switching the switch seem to trigger this phenomenon more? My voltage source is connected to everything in parallel, not serial so on switches or pots value should not affect the other.

Can anyone shed light into this problem?

I had a similar problem with a midi controller that I built using Doepfer boards. As you suspect, it turned out to be a soldering issue. If the input pins are left floating, then the outputs behave exactly as you describe. Check all the connections to all the pots and switches - then check them again. Also check the power supply. If the supply to the pots is fluctuating, then the value of the cc being sent will also fluctuate.

I have tested both of those (I’m working with lemmings). The input voltage is steady. Resoldered everything. It is happening to almost every potentiometer on the board, so it is not just a broken pot.