One pot to control 4 points of resistance? - Page 1
Forum section: electronics / beginners

author: mike-k
author_rank: Contributor
timestamp: March 29, 2021, 06:24:20 pm
content: Hi,I have a circuit with 4 identical sections. There is a resistor of the same value in each section. I would like to be able to vary that value simultaneously across all 4 sections, using a single potentiometer. Can anyone suggest an approach?I was originally going to switch between two fixed resistance values and had a plan to use a demux chip in order to introduce an extra parallel resistor in each of the four sections when a switch was toggled. I'm not sure how to introduce continuous variable resistance however.

author: themadhippy
author_rank: Super Contributor
timestamp: March 29, 2021, 06:38:35 pm
content: QuoteA 4 gang pot

author: mike-k
author_rank: Contributor
timestamp: March 29, 2021, 07:57:02 pm
content: Unfortunately space is tight so that isn't an option - I'm using a small pcb mounted pot.

author: TimFox
author_rank: Super Contributor
timestamp: March 29, 2021, 08:20:20 pm
content: How close do they have to match? Could you use 4 LED-CdSe opto isolators (photo resistor output)? The response time might be a problem, and they have other features including temperature sensitivity. One source is API, Advanced Photonix, available through Newark.

author: mike-k
author_rank: Contributor
timestamp: March 29, 2021, 09:20:12 pm
content: Interesting idea - the resistors control the attack time of voices in a synthesizer. Some small variations might actually be interesting, but ideally they would be identical.

author: sleemanj
author_rank: Super Contributor
timestamp: March 29, 2021, 09:31:19 pm
content: 4 digipots and a microcontroller

author: tpowell1830
author_rank: Frequent Contributor
timestamp: March 29, 2021, 11:53:46 pm
content: quad op amps with unary gain.

author: drussell
author_rank: Super Contributor
timestamp: March 29, 2021, 11:57:38 pm
content: Quote from: mike-k on March 29, 2021, 06:24:20 pmQuote from: mike-k on March 29, 2021, 09:20:12 pmWhat sort of signal are these varying resistances being required to carry?

author: Jwillis
author_rank: Super Contributor
timestamp: March 30, 2021, 08:15:14 am
content: How much restriction to space do you have? There are small 4 gang PCB potentiometers available .PTD904

author: mike-k
author_rank: Contributor
timestamp: March 30, 2021, 02:54:24 pm
content: Thanks for the suggestions. I will have to do some research into the different options. @Jwillis I probably could fit in these Bourns pots, so that might be the most straightforward option.@drussell I don't have a schematic for the circuit so I can't provide much detail. It's a 12VDC powered circuit, requiring min 0.4A. There's more info. here:https://somasynths.com/lyra-8-diy/See 'Tweaks.jpg' in the documentation - this gives a board layout and guide for making mods. I want to modify attack of voices 1 - 4 with one pot and 5 - 8 with another.

author: tggzzz
author_rank: Super Contributor
timestamp: March 30, 2021, 03:36:27 pm
content: Use four voltage/current controlled amplifiers, each with the same control voltage/current defined by your your pot.