Add pots in series to an existing board? - Page 1
Forum section: electronics / beginners

author: Renegade
author_rank: Regular Contributor
timestamp: February 04, 2016, 06:44:50 am
content: I want to add several pots in series to this board:http://www.aliexpress.com/item/Z116-LM2577S-LM2596S-DC-DC-Step-Up-Down-Boost-Buck-Voltage-Power-Converter-Module/32243179400.htmlI've desoldered the existing trim pots, added in some new connectors and wires, but I don't think I can add more than 1 pot in there.e.g. A 1k and a 10k pot for a fine and course adjustment.Can I do it, or not?From what I know so far, it's not feasible. Only 1 pot is possible. s

author: Rerouter
author_rank: Super Contributor
timestamp: February 04, 2016, 07:18:16 am
content: a resistance is a resistance, no matter how many individual resistors make up that value, so pots in series should be fine.

author: Ian.M
author_rank: Super Contributor
timestamp: February 04, 2016, 07:35:50 am
content: Trace the connections on the board and compare with the datasheet of the actual switched mode chip used. If there are only two connections to a pot (although one may go to two pins), you can put the replacement pots in series wired as variable resistors. If however there are three separate connections to a pot, it is almost certainly being used as a true potentiometer and series connection is not possible unless one of your replacement pots is dual gang so you can use its two sections as variable resistors, varying in opposite directions, in series with each of the track ends of the other pot. N.B. the two sections MUST NOT share a common pin at one track end..

author: tooki
author_rank: Super Contributor
timestamp: February 04, 2016, 09:26:44 am
content: Another option for getting fine control is to use a multi-turn pot. That's a drop-in replacement for the existing one.

author: Renegade
author_rank: Regular Contributor
timestamp: February 04, 2016, 05:07:17 pm
content: Quote from: tooki on February 04, 2016, 09:26:44 amThat's starting to look like a good option.Quote from: Ian.M on February 04, 2016, 07:35:50 amYou lost me at that point. (Continued below.)I tried to figure out where the 3rd connection went on the circuit board for the voltage adjustment, but couldn't figure it out. The board has more than 1 layer, with at least the top and bottom used. However, my guess is that it isn't wired anywhere - it doesn't appear to be.For the two current pots, the 1st current pot has its third connection wired to the 3rd pot's second connection (wiper). However, I don't see the first connection on the 1st pot wired to anything. I'm thinking I should just leave the current pots as singles and not bother trying to get an fine/coarse adjustment there. Or at least not until I've developed some better skills.Quote from: Ian.M on February 04, 2016, 07:35:50 amI know what a dual gang is, but beyond that, I was completely lost there with no idea how to wire that up.Anyways, is this the proper way to wire up 2 pots in series? (Image attached.)

author: alsetalokin4017
author_rank: Super Contributor
timestamp: February 05, 2016, 01:41:25 am
content: If your Pin 3 of the existing pot is not connected to _anything_, or if it is _only_ connected to the same pot's Pin 2, then yes, it is correct.But if all three pins of the existing pot are connected to various points in the main circuit, then you probably should not try to connect another pot to it. Use a ten-turn pot of the same value in place of the existing pot instead.