What happens if I use two 10k pots as voltage divider in parallel?

Thread Starter

LikeTheSandwich

Joined Feb 22, 2021
110
So basically that's the question. For example, if one is set to 5k, right in the middle, what will happen as I adjust the other one? Will it effectively cut the range in half, so I'd lose the highest and lowest quarter of voltage readings? Or some totally different behavior?
 

Thread Starter

LikeTheSandwich

Joined Feb 22, 2021
110
That's some weird behavior. I just tried it, and one pot is almost acting like a master and the other is like a modifier. When master is set to 5k, modifier has the behavior I predicted. But regardless of what modifier is set to, master will drag the voltage all the way to 0% and 100% for some reason. All I did was use a breadboard, 2 10k pots, a power supply, and my multimeter. Weird behavior.
 

Ian0

Joined Aug 7, 2020
4,169
Exactly how have you got them connected?
I often a stereo pot with both sections connected in parallel, for no better reason that it attaches more firmly to the pcb.
(It also provides a failsafe in case one wiper becomes detached)
You can also connect them as "coarse" and "fine".
 

Thread Starter

LikeTheSandwich

Joined Feb 22, 2021
110
Exactly how have you got them connected?
I often a stereo pot with both sections connected in parallel, for no better reason that it attaches more firmly to the pcb.
(It also provides a failsafe in case one wiper becomes detached)
You can also connect them as "coarse" and "fine".
Should be just plain parallel.
Coarse/fine isn't really needed for my application. When I get the setup figured out better I'll start a new thread with my specific question(s) about what I need.
 

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KeithWalker

Joined Jul 10, 2017
2,100
So basically that's the question. For example, if one is set to 5k, right in the middle, what will happen as I adjust the other one? Will it effectively cut the range in half, so I'd lose the highest and lowest quarter of voltage readings? Or some totally different behavior?
I you don't understand why you are getting those results, you need to read up on Ohm's Law and series/parallel resistors. Then you will understand.
 

RayB

Joined Apr 3, 2011
17
Play with the simulator: https://www.falstad.com/circuit/circuitjs.html

2 Pots:
$ 1 0.000005 10.20027730826997 50 5 43 5e-11
s 384 80 448 80 0 0 false
v 448 352 448 80 0 0 40 5 0 0 0.5
174 384 80 176 80 1 10000 0.5495000000000001 Resistance
w 384 80 384 160 0
w 160 80 160 160 0
174 160 160 368 160 1 10000 0.46040000000000003 Resistance
w 272 96 272 112 0
w 272 144 272 112 0
w 448 352 160 352 0
w 160 352 160 160 0
O 272 112 320 112 0 0
g 448 352 448 384 0 0
o 10 64 0 4098 5 0.1 0 1
2_Parallel_Pots.JPG
 

Thread Starter

LikeTheSandwich

Joined Feb 22, 2021
110
I you don't understand why you are getting those results, you need to read up on Ohm's Law and series/parallel resistors. Then you will understand.
I'm quite familiar with Ohm's law, which is why I thought I would get the behavior I thought. Turns out that I was correct.

Also turns out one of my pots is broken, at 0 it's reading about 6k and at max it's reading about 16k. That's probably why the behavior was so weird (and why I didn't make a dead short in my testing).
 

MrChips

Joined Oct 2, 2009
25,066
Also turns out one of my pots is broken, at 0 it's reading about 6k and at max it's reading about 16k. That's probably why the behavior was so weird (and why I didn't make a dead short in my testing).
The most likely reason the pot is broken is because it got blown out when you were messing around with the two pots.

Why are you attempting to do this?
 

djsfantasi

Joined Apr 11, 2010
8,086
He doesn’t have a pot in parallel with a resistor, he has a pot in parallel with a voltage divider.
You’re both off the mark. @RayB had it right in post #11. Take a look at the schematic he used with the Falstad simulator. The TS has always been referring to two pots in parallel, each configured as a voltage divider



Sheesh, sometimes it seems like people don’t read posts before replying!
 

Thread Starter

LikeTheSandwich

Joined Feb 22, 2021
110
Play with the simulator: https://www.falstad.com/circuit/circuitjs.html

2 Pots:
$ 1 0.000005 10.20027730826997 50 5 43 5e-11
s 384 80 448 80 0 0 false
v 448 352 448 80 0 0 40 5 0 0 0.5
174 384 80 176 80 1 10000 0.5495000000000001 Resistance
w 384 80 384 160 0
w 160 80 160 160 0
174 160 160 368 160 1 10000 0.46040000000000003 Resistance
w 272 96 272 112 0
w 272 144 272 112 0
w 448 352 160 352 0
w 160 352 160 160 0
O 272 112 320 112 0 0
g 448 352 448 384 0 0
o 10 64 0 4098 5 0.1 0 1
View attachment 253173
I see. That actually has helped quite a lot, interesting, and thank you.
 
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