Voltage refference circuits using single turn potentiometers - Page 1
Forum section: electronics / beginners

author: Lost resistor
author_rank: Contributor
timestamp: January 15, 2025, 01:48:04 am
content: Hi, i would like to make different style/purpose circuits based on single turn potentiometers.The problem im trying to solve is using them as input devices, ai. setting reference voltage on voltage regulators and so on. The issue is, 10 turn pots. are either pricey, or come in that ridiculously small package with tiny screws. Same goes for multi select switches (encoders).What i would like to achieve are different functions (in reference to turning potentiometer) such as log, exp, linear, but with sensitivity control. more sensitivity in set range ect. using potentiometers. Preferably using as few as possible components, and as ,,simple" ones as possible, ai. 2 pots, resistors, two or single pole latching switches, if necessary diodes and transistors.What i absolutely want to avoid is using stuff like op amps and microcontrollers since it defeats the entire purpose and fun of achieving the desired outcome as simple as possible.Any other suggestions for circuits, their uses, applications as well as using different components are more than welcome.Just to re-state, the idea is to use this in op amp circuits for setting amplification factor, as trimmers, for setting voltage on voltage regulators ect. Where i would want full scale with a single potentiometer, but set up so that its more sensitive in higher or lover range, or having two potentiometer, one for full scale - Vcc to GND, the other one for fine (mili)volt or so adjustment

author: schmitt trigger
author_rank: Super Contributor
timestamp: January 15, 2025, 03:43:54 am
content: A dual pot arrangement, for coarse/ fine adjustment would perhaps be the most cost effective option.Bear in mind though, that the cheapest trim pots have significant both mechanical backlash and temperature coefficients.The point I am making is not to use the cheapest pots you can find, but something in the mid to high range, even if they are single turn.*When I have purchased those cheap Chinese, adjustable power supply boards, the first thing I upgrade is the potentiometer. Many use open frame pots, which are very fragile.

author: Lost resistor
author_rank: Contributor
timestamp: January 15, 2025, 04:29:44 am
content: What exactly do you mean by dual pot arangment? wich one exactly?A solution that came to my mind, to achieve one put full range + second one for fine adjustment, would be to use dual housing pot, and a regular one.Having 1 pin of dual pot conected to Vcc, 2 (slider contact) pin to pin 1. of regular pot. Pin 2 of regular pot would be the output.Pin 3 of it would be connected to 2. pin (center) of second pot inside dual pot (if that makes sense). Now the finall out going to GND from that pot would be sonnected to pin 3.Basically, two pots in dual potentiometer are connected in anti parallel (and used for full range), and in between them, a second potentiometer (order of magnitude smaller) for fine ajusment.What is acheaved by this is that second potentiometer is "floating" inside the range of duall potentiometer.

author: ledtester
author_rank: Super Contributor
timestamp: January 15, 2025, 05:10:25 am
content: Quote from: Lost resistor on January 15, 2025, 04:29:44 amHere's one not so obvious idea:https://electronics.stackexchange.com/a/144540/95488See the other answer for more discussion on this idea.Here's another one which uses a dual gang pot for the fine adjustment (as well as some other ideas):http://www.h4ck.de/content/CFPoti/CFPoti.html

author: Lost resistor
author_rank: Contributor
timestamp: January 15, 2025, 05:52:34 am
content: funky, weird and interesting ideas, exactly what im looking for, thanks a lot!!

author: JohanH
author_rank: Frequent Contributor
timestamp: January 15, 2025, 09:56:11 am
content: Quote from: ledtester on January 15, 2025, 05:10:25 amThat's a really nice solution when you need a precision voltage divider.It's a shame that good, concentric (with dual shafts and knobs) dual potentiometers are so rare nowadays. I've found a few Clarostat and Bourns on ebay. The better ones can even be modified (held together with screws), and you can change the individual pots to a different value.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 15, 2025, 12:59:24 pm
content: One option could be combining 1 pot with a Kelvin varley type divider with switches. 1 stepped switch could nearly make up the difference from 1 turn to 10 turns. The cheap switches are 6 positions for 2 poles. So one may need 2 switches. Compared to a high resolution true KV divider one would not need super accurate resistors.