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Old February 6th, 2020, 05:03 PM   #1
lesmar96
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22mm keyed potentiometer

I have a customer who has requested a keyed 22MM potentiometer on his enclosure to provide speed reference for the VFD.

Basically to prevent unauthorized folks to adjust the speed. My common suppliers do not seem to offer this. Have you seen or used any? Any suggestions?
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Old February 6th, 2020, 05:12 PM   #2
GaryS
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I have ever even heard of a keyed pot. Pots are not used much anymore now that most thigs have gone digital.
You may try to use a key activated 3 position spring return to center selector switch and use the ram up / down function of the vfd
it would meet the their needs and simple to find and setup.
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Old February 6th, 2020, 05:16 PM   #3
lesmar96
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I had thought of that as an option, but first I wanted to explore what he asked for first.
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Old February 6th, 2020, 05:49 PM   #4
James Mcquade
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can you put a keyed switch in vfd for permission?
can you put a locked cover over the speed pot?
I have used keyed enclosure door handles before.


just some ideas.
James
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Old February 7th, 2020, 04:02 AM   #5
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Schneider Electric have 22MM potentiometers:

https://www.se.com/us/en/product-ran...849+2427091364
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Old February 7th, 2020, 04:21 AM   #6
rdrast
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Put a normal pot in a lockable box.
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Old February 7th, 2020, 06:43 AM   #7
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Something like this maybe:
https://www.amazon.com/Master-Lock-S.../dp/B00BD9PFHA
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Old February 7th, 2020, 07:10 AM   #8
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That Amazon box has a nice look, but from my experience it would be smashed within 10 to 15 minutes. Plus, from experience with waitresses and locked thermostat covers, a knife would slide in the edges and be able to turn the pot - but not a fine control so probably too much.

I would put a regular lockable plastic enclosure.
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Old February 7th, 2020, 07:34 AM   #9
lesmar96
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He does want the pot on the outside of the enclosure, but just prevent unauthorized people from using it.

Have any suggestions for a good 22MM lockable cover?
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Old February 7th, 2020, 07:41 AM   #10
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As stated, in my 22 years on the shop floor. It would be smashed in days. That being said, if it's not to be messed with. Why not leave it in the panel? Lock the panel? Or talk them into an HMI and password protect it.
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Old February 7th, 2020, 08:14 AM   #11
Steve Bailey
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Keyed switch on the control panel next to the pot. Pot signal wired to a PLC analog input. PLC analog output is actual speed reference to the drive. Logic in the PLC program to transfer the pot signal to the reference when the keyswitch is on, otherwise leave the reference unchanged. Perhaps an illuminated keyswitch to warn the operator of a large difference between the pot setting and the actual reference due to pot twiddling without the keyswitch. That's complicated enough to maybe convince the customer that its easier to accomplish what they want (speed changes only by authorized people) using an HMI.
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Old February 7th, 2020, 08:31 AM   #12
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Automation Direct

Padlockable, 6x6 box, $75
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Old February 7th, 2020, 03:46 PM   #13
lesmar96
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Quote:
Originally Posted by Steve Bailey View Post
Keyed switch on the control panel next to the pot. Pot signal wired to a PLC analog input. PLC analog output is actual speed reference to the drive. Logic in the PLC program to transfer the pot signal to the reference when the keyswitch is on, otherwise leave the reference unchanged. Perhaps an illuminated keyswitch to warn the operator of a large difference between the pot setting and the actual reference due to pot twiddling without the keyswitch. That's complicated enough to maybe convince the customer that its easier to accomplish what they want (speed changes only by authorized people) using an HMI.
I had thought of something similar to this. They would like to be able to adjust the speed with gloves on, thus we are sticking with the pot and not going HMI all together. They will have to decide between all their wants and their needs.

Thanks for your help again!
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Old February 7th, 2020, 04:12 PM   #14
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Quote:
Originally Posted by lesmar96 View Post
They would like to be able to adjust the speed with gloves on
Then how would they get a key in the lock?

Suggest the key switch method to adjust as mentioned, but instead of a key switch use a RFID identification stick.
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Old February 7th, 2020, 04:16 PM   #15
lesmar96
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Quote:
Originally Posted by Aabeck View Post
Then how would they get a key in the lock?

Suggest the key switch method to adjust as mentioned, but instead of a key switch use a RFID identification stick.

From my experience a keyed selector switch would be workable with gloves on, although the RFID idea is not a bad one
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