We would like to show you a nice solution for an industrial potentiometer, AKA “Speed Pot”, to use for controls systems, especially for controlling the speed for Variable Frequency Drives.
Typically, users would install a standard panel mount potentiometer, such as this one. This solution works fine, however, many potentiometers do not fit into standard 22mm push-button knockouts typically found in control panels. Also, the potentiometer terminals require soldering, which is tedious to do in the field.
We have been on the lookout for a potentiometer that is easy to use, high quality, requires no soldering, and fits a 22mm push-button knockout. This search has led us to many solutions, which we have tried, and have finally settled on a good solution. Let us explain:
There are indeed panel mount potentiometers available that fit a 22mm knockout, and have built-in terminals that require no soldering.
For example,
This one from Automation Direct, a popular direct to end user sales outlet:
This unit is very low cost, and seems to work well, and we have used several, however it is made very cheaply, and doesn’t provide the quality image that we like to have. Also, it requires a separate legend plate, sometimes there is not physical space for a legend plate.
There are several other brands available, such as ABB, Eaton Cutler Hammer, C3 Controls, and Allen-Bradley. Most of these are high quality, and work well. They are all of the type pictured above, using an integrated non-replaceable potentiometer. As such, if you need a range of potentiometer resistances, such as 2.5k, 5k, 10k, etc…you need to buy a complete unit for each resistance.
Here is what we have settled on as our standard panel mount potentiometer, It is a very high quality solution, looks good, and suits all applications. It is a little more work to put together than the others, and more expensive, but we feel that it is worth it.
Fist of all, you need the potentiometer base from Schneider Electric:
http://www.alliedelec.com/schneider-electric-zb4bd922/70008096/
This is made in France, all metal, and has a built in legend marking plate for potentiometer position.
Also you need a potentiometer with a 1/4″ x 2.5″ shaft, we use one from Claro/Honeywell. Choose your resistance:
http://www.alliedelec.com/honeywell-53c12500/70153086/
This is made in Mexico by Honeywell, very good quality, and is field replaceable. Notice that the potentiometer has solder lugs. We want to have screw terminals for ease of field wiring. So the last item to purchase is a terminal block to solder to the potentiometer.
We recommend these, they fit the lug spacing on the potentiometer perfectly:
https://www.amazon.com/uxcell®-Terminals-Terminal-Blocks-Connectors/dp/B0079SL1JK
Once you have all items on hand, insert the pins on the terminal block into the lugs on the potentiometer and solder it into place. Now, you have a potentiometer with screw terminals!
Then, use the instructions included with the potentiometer base, and fasten the potentiometer into the base:
Next, assemble the unit into your 22mm knockout. We used this on a recent job, replacing a failed potentiometer. Here is the backside of an old potentiometer with solder lugs.
Old Way!
Here is the front and back of the new potentiometer, no soldering required in the field, and is an industrial, long lasting solution, with easily replaceable potentiometer.
New Way!
Hopefully this was helpful! Thanks for reading.