High friction potentiometer - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: May 11, 2016, 08:07:50 am
content: I have what seems to be an unusual request. even putting "high friction" into google gets me results for low friction pots. I need a high friction potentiometer to put into a vehicle that has a lot of vibration. The knobs are quite heavy so the usual pot tends to move on it's own. Are there any "hard to move potentiometers" out there ?

author: Fungus
author_rank: Super Contributor
timestamp: May 11, 2016, 08:14:57 am
content: https://encrypted.google.com/search?q=push+lock+potentiometer(edited to a general google search - was no longer available at the original link)

author: Simon
author_rank: Unknown
timestamp: May 11, 2016, 08:18:28 am
content: thank you but a bit too elaborate and no longer available

author: Kjelt
author_rank: Super Contributor
timestamp: May 11, 2016, 08:21:50 am
content: Never heard of those. That sounds like an application you nowadays would use incremental encoders for.A mechanical solution would be to fasten the axis with some kind of ring around the axis that a screw tightens (seen those in the old days).

author: Fungus
author_rank: Super Contributor
timestamp: May 11, 2016, 08:27:41 am
content: Quote from: Simon on May 11, 2016, 08:07:50 amUse lighter knobs?

author: wagon
author_rank: Frequent Contributor
timestamp: May 11, 2016, 08:28:05 am
content: My suggestion is you put a seal nut like this on ithttp://au.element14.com/apm/n9030-1-4/seal-rotary-shaft/dp/146839It should provide enough drag to stop it moving by itself. Can you make the knob lightweight too?

author: alanb
author_rank: Frequent Contributor
timestamp: May 11, 2016, 08:31:08 am
content: How about some friction material between the back of the knob and the facia. A felt disc for example or a piece of Velcro.

author: Simon
author_rank: Unknown
timestamp: May 11, 2016, 08:36:05 am
content: Quote from: wagon on May 11, 2016, 08:28:05 amGood idea. We have made the knob as light as possible and as balanced as possible.

author: amspire
author_rank: Super Contributor
timestamp: May 11, 2016, 08:37:05 am
content: You could replace the potentiometer with a 12 position switch plus some resistors, if you do not need precision settings.

author: Simon
author_rank: Unknown
timestamp: May 11, 2016, 08:37:25 am
content: Quote from: alanb on May 11, 2016, 08:31:08 amYes I've been trying to think of a clean nice way to do that, I did think of a sling of some sort.

author: Ian.M
author_rank: Super Contributor
timestamp: May 11, 2016, 08:38:06 am
content: Quote from: Kjelt on May 11, 2016, 08:21:50 amYes. e.g.http://www.alliedelec.com/keystone-electronics-1701/70181400/However that's a shaft locker, and if you adjust it for controlled friction, the amount of froction is likely to vary considerably with wear and possibly temperature. It *MAY* be satisfactory with a dab of Kilopoise grease on the shaft.https://www.rocol.com/products/kilopoise-high-viscosity-damping-greaseThe locking nut will need something to stop it shifting as well. The other issue is it needs a recessed mounting for the pot or a tall knob with a cavity for the locker.Personally, I'd look at adding friction behind the knob. e.g. a felt washer + some Kilopoise grease or spring loaded plastic plungers fitted in the knob, bearing on the panel or fitted in the panel bearing on the knob.

author: Simon
author_rank: Unknown
timestamp: May 11, 2016, 08:38:29 am
content: Quote from: amspire on May 11, 2016, 08:37:05 amWell I'm actually trying to get rid of multi position switches as pots are cheaper and easier to wire up with less wires required or the need to soldering all of those resistors on.

author: Simon
author_rank: Unknown
timestamp: May 11, 2016, 08:39:49 am
content: Quote from: Ian.M on May 11, 2016, 08:38:06 amProblem is I have a panel mounted pot and anything I do will be on the front panel visible to the customer.

author: wagon
author_rank: Frequent Contributor
timestamp: May 11, 2016, 08:42:41 am
content: Quote from: Simon on May 11, 2016, 08:36:05 amI've used those seals on pot-shafts fitted to machinery like vibrating rollers and such. They seem to work OK.

author: alanb
author_rank: Frequent Contributor
timestamp: May 11, 2016, 08:43:55 am
content: Quote from: Simon on May 11, 2016, 08:37:25 amI would go for a flat disc rather than a sling. For extra friction use two discs on glued to the back of the knob and the other glued to the facia

author: jdraughn
author_rank: Regular Contributor
timestamp: May 11, 2016, 08:47:14 am
content: Try this search string in google:+"high friction" potentiometer

author: Simon
author_rank: Unknown
timestamp: May 11, 2016, 09:08:21 am
content: Quote from: jdraughn on May 11, 2016, 08:47:14 amand it keeps bringing up the same 250K audio (log) pot. I'm looking for something around 1-10K linear.

author: Kjelt
author_rank: Super Contributor
timestamp: May 11, 2016, 09:15:16 am
content: Or you can do something mechanical like mount the potmeter further inside the device and use some kind of bearing to guide the axis and on that bearing you create a side hexnut screw to highten the movement friction. But that is a large mechanical redesign step I guess.

author: Simon
author_rank: Unknown
timestamp: May 11, 2016, 09:16:09 am
content: Quote from: Kjelt on May 11, 2016, 09:15:16 amYes we have already thrown that idea out.

author: tautech
author_rank: Super Contributor
timestamp: May 11, 2016, 11:03:53 am
content: Quote from: alanb on May 11, 2016, 08:31:08 amThis is theclassicmethod. ^^^^Seen it lots of times.Something like 1.5mm felt and a flanged knob that allows a large surface area for the friction required.A push on knob allows easy adjustment of friction while a set screw type provides precise adjustment.Time for a trip to a fabric shop Simon.........do dress accordingly.

author: rs20
author_rank: Super Contributor
timestamp: May 11, 2016, 01:27:14 pm
content: I think the term you're looking for is "high torque", as the relevant spec in datasheets is given as a torque (why require the end user to know the internal normal force and moment arm that's required to convert a friction coefficient to a torque, the torque is what the end customer  care about?).For example, the first result I got for "high torque potentiometers" wasthis page, which on page 2 list the Vishay PE30 and PRV4 parts with "high torque" as a specific feature, and "Off road" as a suggested application. I'm sure you could find many more, I've literally only looked at the first search result.Having said all that, I do endorse the point of view that providing holding torque is not a requirement of the pot, if you arrange your own friction device separately you'll have much more control.

author: Jeroen3
author_rank: Super Contributor
timestamp: May 11, 2016, 01:44:03 pm
content: You attach a lockable dial. "potentiometer dial lock".Or you ask Bourns.

author: Farley
author_rank: Regular Contributor
timestamp: May 11, 2016, 02:35:57 pm
content: Could a spring washer be integrated into your design?https://www.springmasters.com/spring-washers.html

author: Cerebus
author_rank: Super Contributor
timestamp: May 11, 2016, 03:02:53 pm
content: Quote from: Simon on May 11, 2016, 09:08:21 amArrived in the post here today a 'Bourns' 10 turn 10k linear wirewound pot for £3 off ebay. At that price, if it was actually made by Bourns in Mexico then I'm a Chinaman - as I suspect was the original manufacturer. But I knew what I was getting and I just wanted to see what £3 would get me.That detail aside, it's actually decent quality and has a smooth heavy feel that I suspect would be very vibration resistant. I had to put a collet knob on it just to test it as moving the shaft by hand was hard work. As a bonus, easily settable to 0.1% and just about settable to 0.01%. The 10 turn nature of the pot might be an issue for you, or it might be a bonus. If it's an issue, think about whether a diode clamp or similar might mitigate the problem.

author: m98
author_rank: Frequent Contributor
timestamp: May 11, 2016, 05:57:44 pm
content: You could consider those "pull-out to turn" pots. They work great and can't be changed by accident.

author: Unknown
author_rank: Unknown
timestamp: May 12, 2016, 01:00:33 am
content: Maybe a bellevue washer/nut arrangement can be fashioned on the shaft? Same principle that's used to maintain the throttle position on my tractor.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 12, 2016, 09:53:40 am
content: I had the same problem for a race car, that was shaking a lot, where I needed a 10k potentiometer very stable and I found one.Our local store gave me the opportunity to try all potentiometers they had in stock.And one of them had pretty high friction and worked perfectly.It is made byWeltronhttps://www.conrad.de/de/dreh-potentiometer-mono-04-w-10-k-weltron-wp20cs-08-60f1-10k-20-lin-100-st-437443.html