Analog pots dont go to zero

[Harry-Butter]

Hi! This seems like a pretty common problem, but I haven't found the answer her on the forum, so... I've made a box for my axoloti with analog potentiometers connected to the gpio's... Its been working smoothly, but I'm noticing that the values never go to 0 even though the pot is fully counterclockwise. They go to 1.2 something.. I've tried different pots and they seem to all have the same issue. Dividing the input doesn't help much. Someone help me!

[Gavin]

I guess its not impossible for some brand of pots to be designed to not go to absolute zero if connected to an analogue input. What does the maximum go to .. does it go all way ?

[Ersatzplanet]

The value of the pot and the voltage it is given to divide will determine if the voltage goes to 0 if only the pot and voltage are connected to the pot (using 2 legs).The pot resistance is the only thing lowing the voltage and it can easily not be high enough to remove it all. If you use all three legs of the pot - one to the voltage source, the middle to the Axo input, and the third leg to ground, turning the pot to the ground end should give you 0 Volts. If it doesn't show as that, then it is in the programming somewhere. At the ground end of the pot it should be shorted out producing no voltage at all.

[Harry-Butter]

So I guess there is maybe something wrong with my wiring.... Ill run a quick test on my breadboard and try to compare...

[Gavin]

You may want to read through this, its got some details on wiring etc that may be of some use..

Official Pin Outs revised (work in progress)

I'll be working on revising this post here, I was going to write it in a text document but realized it would be easier for me to get all the images if I just made it here. I was looking for a a save feature so I could wait to post until complete but could not find it. So please note this is all a work in progress and NEEDS further revision/information. GPIO Overview [image] VDD versus VDDA versus VDDC VDD is the digital 3.3V supply, use it to power external logic VDDA is the analog refe…

[sevo]

The regular spec of affordable pots would be "1:10 range, with 5% or 10% accuracy when differentially connected (i.e. GND to Vcc across the pot)". 1.2k would be slightly worse than 10% on a 100k pot, but that might be due to open-ended connection. If you really need a huge working range at high accuracy, be prepared to spend significant amounts of money.

[damonp]

use this:
if (inlet_in>=param_c) {outlet_out=inlet_in;}

[damonp]

Here, as I have a similar problem I wrote this real quick to help...
the gate gives you a bottom threshold and the smooth... smooths it.
smoothgate.axo (886 Bytes)
And here it is for 8 in/out:
smoothgate8.axo (2.3 KB)

[Harry-Butter]

Youre my hero. thanks a lot

[damonp]

I personally have the gate set to 1 and the time for the smooth around 60, this works well for what Im doing... but your mileage may vary.