I have connected 4, 10k linear potentiometers in parallel with +5v and Gnd from the Arduino. The middle pin on the potentiometers are connected to a 4051 multiplexor.
In my sketch I analog read the multiplexor in sequence and I get a value of each potentiometer witch i use to map different notes to a CV-sequencer.
Everything seem to work alright until i crank all the pots to max. And let alot of current through. Then suddenly I see a drop in output from them.
What am I doing wrong? should i buffer the output from the multiplexor or is my power suply to weak?( I just power the arduino from usb.) Should I in some way rethink my setup?
until i crank all the pots to max. And let alot of current through.
You don't let a lot of current through at the top if it is wired up right. If you are seeing a voltage drop with the pots at one end it sounds like you have miss identified the wiper. The analogue input is a high impedance and you will not see any significant current draw from them.
ok this is exactly what happens. the pots are read one by one and the value are displayed on a lcd i hooked up to the arduino. so when I start to turn up pot one to max a get a value of 255. The others are zero. I turn up pot 2: 255. and then i turn up put 3 to 255. but when I turn all 4 pots to max i i suddenly start getting 215, 225 ,210 and all sorts of values from all pots. It does not matter what pot i start with.
Ok that's what you see and I don't doubt you, but the plane truth is that you shouldn't see that. I am not sure if this is a layout problem or that you haven't got what you think you have.
So first off I would put a 0.1uF decoupling capacitor across the 4051, then I would put a 0.1uF across the arduino's analogue input to cut down any noise. Finally I would put a decoupling capacitor across the 0 and 5V on the pots.
You could also try a 47K pull down on the analogue input to ground as there might be some leakage problems. Likewise you could introduce a small delay between switching the 4051 and taking the reading.