SOLVED: Wiring of 6 pots to Arduino

Using Arduino General Electronics
1

Hi all,

I'm making a control box with 6x10k linear potentiometers. I have checked that they are all 10k and working.

I have daisy chained them together with all + legs and all - legs connected. The problem is now that when I check the resistence over the plus and minus leg of any pot, the resistance is only 2 kOhm. And the value from minus to signal leg varies in a parabola starting from 0 going to 3.2 kOhm and down to around 2 kOhm.

I have a hard time understanding why this is and I don't think that this setup would give the desired result...

I have attached a picture of the soldering. I checked all connections for continuity and all is good.

I would of course then attach a single + and - wire to the arduino and the signal wire form each pot to the analog inputs.

foto.JPG
foto.JPG480×640 108 KB

2

I have a hard time understanding why this is

No problem just google resistors in parallel.
It will work fine.

3

zenseidk:
I have daisy chained them together with all + legs and all - legs connected. The problem is now that when I check the resistence over the plus and minus leg of any pot, the resistance is only 2 kOhm.

That's because you're measuring them when they're all connected together in parallel.

4

When you connect them to +5 & Gnd, they all still return the desired Voltage reading tho, yes? That's all the analog input cares about.

5

Hi all,

Yes, I realise that resistors in parallel is not 10kOhm, but 1/(1/R1+1/R2+1/R3+...1/Rn), but when I measure from GND to signal I also don't get 10 kOhm, but rather the parabola I wrote about before. And that is what I don't understand... I would expect to still have 0 to 10 kOhm when measuring from GND to signal.

Or am I mistaken on that?

6

And that is what I don't understand... I would expect to still have 0 to 10 kOhm when measuring from GND to signal.

Your expectations are wrong.

Forget measuring resistance, power it up and measure the voltage on the wiper they will all go from 0 to 5V.

In fact the value of the pot does not matter all that matters is that they go between the rails. I often use 24K pots because they were the cheapest when it came to purchasing them in bulk.

7

Using that many pots, dont forget decoupling caps. :slight_smile: Will allow you to use higher resistance pots and all.

8

How can you get 10K when you have the equivalent of a 2K resistor (from the other 10Ks in parallel) across the legs of your 10K resistor?
You have the equivalent of this:

| |

2K > 5K
< <
| |
| |---
| |
| > 5K
| <
| |

with your pot at mid scale.
So measuring between junction of the 2 5K pots and a leg is like
measuring a 5K in parallel with a 7K
= 1/(1/5000 + 1/7000) = ~2.9K

9

All right, I give :slight_smile:

I have connected it up and everything works... Thanks!