Looking for good pot :)

TimothyMoulder · Jul 21, 2011

Sorry, I just couldn't resist...

I have an application where we monitor a test machine's position with a 10k single-turn potentiometer - the classic volume knob variety. Nothing special there, but the machine is subjected to high levels of vibration in the testing process, which makes short work of the cheap dime-store pots we've used up to this point.

I'm shopping around for something more durable, preferably with a reinforced element and bearing-mounted shaft. I don't need something to last forever, but it would be nice to get more than a couple weeks out of it.

I'm hoping somebody here faced a potentiometer vibration issue, and can recommend a reliable company to do business with.

Thanks,

TM

iant · Jul 21, 2011

you'll get what you pay for -
RS components have a number of ranges
also look for a vernier knob with lock
Alternative modify control to analogue smart relay or PLC.

Steve Etter · Jul 21, 2011

How about remote mounting the pot? If it is a machine that stays in your shop, you could make that a permanent change. If you are building and testing a machine for a customer, I should imagine you could test everything else while the pot is remote mounted and then move it to its final position after all the vibration stuff is done.

Steve

RDS · Jul 21, 2011

I have been using these in an outdoor industrial setting, check it out at http://www.newark.com/honeywell-s-c...d-plastic-10kohm-10-2w/dp/04F8997?Ntt=04F8997

rdrast · Jul 21, 2011

TimothyMoulder said:
Sorry, I just couldn't resist...

I have an application where we monitor a test machine's position with a 10k single-turn potentiometer - the classic volume knob variety.

Well, you do know that the 'classic volume knob variety' is a logarithmic pot, right?

For a durable Linear simple pot, try something like this:
http://sensing.honeywell.com/index.cfm?ci_id=140301&la_id=1&pr_id=151799

TimothyMoulder · Jul 21, 2011

D'oh! RD is exactly right - it's been alot of years since school.

Thanks for all the suggestions. This test rig shakes to death as a side effect of what is being tested. I'm not at liberty to divulge, but as I've stated before, I am employed by a worldwide manufacturer of power tools. Steve suggested a remote pot, and I was looking at a string pot, but the design of the rig makes this tricky.

When I took one of the failed pots apart, I noted it was a real tinker-toy. I take that back - I like tinker-toys, this thing was just cheap junk. So hopefully a more robust pot will take the abuse better. Like I said, I don't care if I have to replace it periodically (it's for in-house use), just not weekly.

I did take note of two votes for honeywell products, so I will resume my search with those links.

Thanks to all!

TM

LadderLogic · Jul 21, 2011

Does it have to be an analog signal and a pot?

This (http://www.bourns.com/data/global/pdfs/ace.pdf) will get you up to 128 Grey code values per rev via 8 discrete lines; converting Grey code to sequential decimals is a trivial PLC task. Yes, it is also cheap plastic - but being a mechanical switch it should not be subject to the vibration effects that much, I guess...

Doug-P · Jul 21, 2011

Would a digital pot work?

http://www.maxim-ic.com/app-notes/index.mvp/id/3970

TimothyMoulder · Jul 21, 2011

Hi again,

Checking into the options discussed. I'm trying to avoid any electronic device like a digital pot, since I think the vibration would long-term shake the components right out of it.

I checked out several resources on the web about the best pot material for dealing with vibration. The highest mark I found was metal film, but I can't locate that in a potentiometer - mainly used for basic resistors, it seems. I did follow LadderLogic's link to Bourns, and their Hybritron product looks interesting (a wire-wound element coated with a layer of conductive polymer to make the resistance changes smoother) but I couldn't find anything about it's vibration resistance.

Still searching. All suggestions welcome!

Thanks,

TM

BTalbot · Jul 21, 2011

They're only singleturn but the Turck analog encoders hold up in some nasty enviroments. (yes I work for a Turck distributor but nowhere near Florida, just trying to help).
http://turck-usa.com/Products/Encoders/Absolute/Singleturn/Analog.htm

ndzied1 · Jul 21, 2011

TimothyMoulder said:
Sorry, I just couldn't resist...

TM

Funny, my first thought was not of the 5 leaves plant but of the electronic thingy dingy you are looking for. I guess I qualify as geek.

I wonder if anyone makes a mini resolver for panel mounting. Those are used a lot on motors that need a rugged feedback. I don't have Internet besides my phone for a few days so an extensive search is out for me.

ndzied1 · Jul 21, 2011

One more thought. Do you really need a pot? Can you use UP/DOWN push buttons through a controller to generate the analog signal?

These have no moving parts:
http://www.itwswitches.com/touchsensors.shtml

But I have never tried them...

keithkyll · Jul 21, 2011

I would go with wirewound. Look at Vishay/Spectrol. This one is rated for 20 G's. There are many others in the Vishay line.

dploof23 · Jul 22, 2011

I had some issues with vibration and speed pots. I was using the cheap ones too....switched to Allen Bradley panel mounted pots, (standard 30.5mm switches) and haven't had an issue yet...knock on wood

Dave

shooter · Jul 22, 2011

go for optical, it will withstand any vibration, and as you want it cheap even an old mouse will do, find an serial mouse and put the counts in a counter.

oh sorry it is just single turn.
make one yourself with a perspexdisc a marker and a light and LDR.
you will need a little experimentation on how far the marker has to black the disc up but it is vibration proof.
use a small capacitor on the output to get a nice signal.
you could do the same on yours (maybe the vibration is not big enough to lift the runner.

Looking for good pot :)

TimothyMoulder

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