Eaton DE1 VFD drive potentiometer too sensitive .

[cjbouchard@bergco.com]

I have a customer who is running a blower 2hp 3 phase motor in a coffee roaster. I installed a DE1 Eaton drive its a slick set up basic configuration on /off switch and Potentiometer to control the speed of the motor . However the manual for the drive specs out a 1k to 10 k pot . I used a 5k pot and my problem now is it is to sensitive for controlling the speed of the motor . I am researching using a higher value Potentiometer to make the speed control more user friendly . I am unfamiliar with what value Potentiometer to use to be able to get a more controlled range , right now it jumps from 20hz to 50hz if you touch the pot just a little bit and this is very hard to dial the coffee roaster loft to a sweet spot. I was also thinking I used a kb electronics potentiometer it was 3$ for a proto until I dial in the design and maybe its just a have a really cheep potentiometer , The Eaton potentiometer is about 100$ .

 

[ptonsparky]

You need a better one. AD has them as well as others. Don't expect much for $3.

 

[petersonra]

It sounds to me like you have a pot problem. It's not so much that the pot was cheap as it probably has a wiper that is intermittent. You will probably find that you will get better control with a pot that has a lower resistance but not by much it's really about the voltage divider that the pot is giving you. Personally I'm not a big fan of of using potentiometers to control motor speed. Just put the interface module on the door so they can set the speed directly and forget the miserable pot.

 

[gar]

210513-0958 EDT

I used to buy Ohmite 2 W pots for somewhere near $1 to $2 each in small quantities. The price today at about $22 is unreasonable.

There is nothing wrong with a pot used to adjust a good DC motor control. It will provide good control from near zero to full RPM.

It is unlikely that a motor control would use a variable resistor for speed control. If that was the case, then the resistance range would be of importance. Most likely a potentiometer configuration would be used, and this will be used in an adjustable voltage divider configuration. Usually pots used for industrial applications are linear in resistance with respect to angular position of the shaft. Pots used for audio usually have some form of log relationship.

cjbouchard@ber: provide more information on how the pot is connected to the motor control, and how the motor control works with your motor. Do you have a DC motor, or an AC induction motor, or something else. Most induction motors are not suited for much speed control via voltage control. AC induction and synchronous motors need frequency control for any effective speed control.

.

 

[petersonra]

The OP seems to indicate he attached a pot to the analog input of a variable speed drive (the model number he mentioned is a VFD) to control motor speed. Nothing wrong with that. It is done a lot. But if the pot has an intermittent wiper it may not work real well. It could also be wired wrong. Normally the two ends of the pot go to 10VDC and 0VDC (the VFD usually supplies this), and the pot's wiper to the drive analog input designated for the desired drive speed.

Most such drives also have what is called a MOP function where a pair of inputs can be used with up and down push buttons to control motor speed.

 

[cjbouchard@bergco.com]

210513-0958 EDT

I used to buy Ohmite 2 W pots for somewhere near $1 to $2 each in small quantities. The price today at about $22 is unreasonable.

There is nothing wrong with a pot used to adjust a good DC motor control. It will provide good control from near zero to full RPM.

It is unlikely that a motor control would use a variable resistor for speed control. If that was the case, then the resistance range would be of importance. Most likely a potentiometer configuration would be used, and this will be used in an adjustable voltage divider configuration. Usually pots used for industrial applications are linear in resistance with respect to angular position of the shaft. Pots used for audio usually have some form of log relationship.

cjbouchard@ber: provide more information on how the pot is connected to the motor control, and how the motor control works with your motor. Do you have a DC motor, or an AC induction motor, or something else. Most induction motors are not suited for much speed control via voltage control. AC induction and synchronous motors need frequency control for any effective speed control.

.

AC motor though a VFD Drive .

 

[cjbouchard@bergco.com]

The OP seems to indicate he attached a pot to the analog input of a variable speed drive (the model number he mentioned is a VFD) to control motor speed. Nothing wrong with that. It is done a lot. But if the pot has an intermittent wiper it may not work real well. It could also be wired wrong. Normally the two ends of the pot go to 10VDC and 0VDC (the VFD usually supplies this), and the pot's wiper to the drive analog input designated for the desired drive speed.
View attachment 2556552
Most such drives also have what is called a MOP function where a pair of inputs can be used with up and down push buttons to control motor speed.

exactly what I have going on I m using page 72 of the DE1 manual , only using the fWD input pot pot 1 term is going to OV the 2is +10V and 3 is to the 4 Al1/D14

 

[petersonra]

exactly what I have going on I m using page 72 of the DE1 manual , only using the fWD input pot pot 1 term is going to OV the 2is +10V and 3 is to the 4 Al1/D14

Is term 3 the wiper on the pot? Usually pot terminals are labeled a-b-c or 1-2-3 and "b" or "2" is the wiper. The wiper is what should be connected to AI1/DI4.

 

[MD Automation]

pot 1 term is going to OV the 2is +10V and 3 is to the 4 Al1/D14

Hi, I'm just wondering if you have the pot hooked up incorrectly, based on you wiring description above? Typically, the wiper in a pot is pin #2...


And as Petersonra points out above, the wiper is what should be connected to your analog input.

 

[synchro]

I agree with the comments above about the proper connections to the pot. If you connected the wiper of the pot to 10V then you may have damaged it because it would likely draw more current than the wiper can handle (especially when the pot was turned down because then the resistance would be the lowest).


Here's some examples of higher quality pots than what you have:
...

53AAA-C28-E13L Bourns Inc. | Potentiometers, Variable Resistors | DigiKey

Order today, ships today. 53AAA-C28-E13L – 5k Ohm 1 Gang Linear Panel Mount Potentiometer None 1.0 Kierros Conductive Plastic 0.5W, 1/2W Solder Lug from Bourns Inc.. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

www.digikey.com

282T33L502A25C2 CTS Electrocomponents | Potentiometers, Variable Resistors | DigiKey

Order today, ships today. 282T33L502A25C2 – 5k Ohm 1 Gang Linear Panel Mount Potentiometer None 1.0 Kierros Conductive Plastic 0.25W, 1/4W Solder Lug from CTS Electrocomponents. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

www.digikey.com

657BR0502 Vishay Spectrol | Potentiometers, Variable Resistors | DigiKey

Order today, ships today. 657BR0502 – 5k Ohm 1 Gang Linear Panel Mount Potentiometer None 1.0 Kierros Conductive Plastic 1W Solder Lug from Vishay Spectrol. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

www.digikey.com

You basically get what you pay for as far as moisture and dust resistance, rotational life, etc.

After you get another pot be sure to measure the resistance between the two terminals that you intend to connect to the 0V and 10V terminals. It should be close to the rated resistance and not change as you rotate the shaft.

 

[cjbouchard@bergco.com]

Hi, I'm just wondering if you have the pot hooked up incorrectly, based on you wiring description above? Typically, the wiper in a pot is pin #2...

View attachment 2556553
And as Petersonra points out above, the wiper is what should be connected to your analog input.

Yes that is exactly how I have it hooked up >

 

[synchro]

Hi, I'm just wondering if you have the pot hooked up incorrectly, based on you wiring description above? Typically, the wiper in a pot is pin #2...
And as Petersonra points out above, the wiper is what should be connected to your analog input.

Yes that is exactly how I have it hooked up >

Do you have an analog multimeter? If so and the meter scale says it's rated as 20,000Ω/V or more (to prevent loading down the pot too much) then I suggest using it to measure the voltage between the 0V and 4 Al1/D14 terminals as you rotate the pot. The meter's needle should move smoothly and go over the range between 0V and 10V.

 

[zbang]

What does "too sensitive" mean? A small turn of the pot makes a big change in RPM? A better pot, a 5-turn instead of single-turn, or a bias resistor could all help. (I kinda like biasing the range with a small resistor since often they're easier for me to come by than a really good pot.)

 

[RumRunner]

The window of error and the resultant outcome of a miswired pot is minimal.
The worst case scenario is the reverse operation of the pot if you miswire the polarity of the extreme ends of the pot.

Another scenario is; you would lose control of the output of the vfd if the wiper is miswired.. . .it will run at a constant speed.
But OP says he can control it only too sensitive.

The recommended valiue of the pot is maxed at 10 k.
However, OP opted to use a max of 5 k instead of 10 k .

Moving the shaft slightly makes it too sensitive. . .as a result of a reduced resistance.

To achieve the resistance recommended by the manual, you could deploy a 4k or 5k resistor in series with the wiper. A one watt or even smaller carbon resistor should work.

 

[Jraef]

Also also also...
VFD speed control pots should be LINEAR, not "tapered". What that means is that the resistance in a linear pot changes at the same rate as you turn the pot, whereas a tapered pot has a logarithmic scale to the resistance change. So with a tapered pot as you get closer to the end of the pot's travel, the change in resistance per degree of rotation is getting GREATER. So a small movement of maybe 10 degrees at the starting point has almost no effect on the VFD speed command signal, whereas at the other end, a small movement of just 2 degrees may change the speed command by 10% or more. I always recommend making sure you get a LINEAR pot to use for VFD speed control. If you didn't pay attention to that issue when you bouth the pot, it might be a tapered pot, also called an "Audio pot". No bueno for this task.

 

[cjbouchard@bergco.com]

Thanks for the input . I going backwards I trying a 1k Pot 1 turn

The window of error and the resultant outcome of a miswired pot is minimal.
The worst case scenario is the reverse operation of the pot if you miswire the polarity of the extreme ends of the pot.

Another scenario is; you would lose control of the output of the vfd if the wiper is miswired.. . .it will run at a constant speed.
But OP says he can control it only too sensitive.

The recommended valiue of the pot is maxed at 10 k.
However, OP opted to use a max of 5 k instead of 10 k .

Moving the shaft slightly makes it too sensitive. . .as a result of a reduced resistance.

To achieve the resistance recommended by the manual, you could deploy a 4k or 5k resistor in series with the wiper. A one watt or even smaller carbon resistor should work.
[/Q

 

[cjbouchard@bergco.com]

Also also also...
VFD speed control pots should be LINEAR, not "tapered". What that means is that the resistance in a linear pot changes at the same rate as you turn the pot, whereas a tapered pot has a logarithmic scale to the resistance change. So with a tapered pot as you get closer to the end of the pot's travel, the change in resistance per degree of rotation is getting GREATER. So a small movement of maybe 10 degrees at the starting point has almost no effect on the VFD speed command signal, whereas at the other end, a small movement of just 2 degrees may change the speed command by 10% or more. I always recommend making sure you get a LINEAR pot to use for VFD speed control. If you didn't pay attention to that issue when you bouth the pot, it might be a tapered pot, also called an "Audio pot". No bueno for this task.

Thank you for the Information. Today I will try mac master carr p/n 7436K37 is the test subject today it is a Linear pot however from some of the comments above I might not get the right function out of it , The good news is I'm having some fun trying to find the sweet spot .If the test today fails I will try this , To achieve the resistance recommended by the manual, you could deploy a 4k or 5k resistor in series with the wiper. A one watt or even smaller carbon resistor should work.

 

[cjbouchard@bergco.com]

Thanks everybody I have found the sweet spot with the new Pot 1k 1 turn from mc master carr p/n 7436k37 works very well ,though out the whole entire range .

 

[garbo]

210513-0958 EDT

I used to buy Ohmite 2 W pots for somewhere near $1 to $2 each in small quantities. The price today at about $22 is unreasonable.

There is nothing wrong with a pot used to adjust a good DC motor control. It will provide good control from near zero to full RPM.

It is unlikely that a motor control would use a variable resistor for speed control. If that was the case, then the resistance range would be of importance. Most likely a potentiometer configuration would be used, and this will be used in an adjustable voltage divider configuration. Usually pots used for industrial applications are linear in resistance with respect to angular position of the shaft. Pots used for audio usually have some form of log relationship.

cjbouchard@ber: provide more information on how the pot is connected to the motor control, and how the motor control works with your motor. Do you have a DC motor, or an AC induction motor, or something else. Most induction motors are not suited for much speed control via voltage control. AC induction and synchronous motors need frequency control for any effective speed control.

.

Back in the 1980's we used a cheap Ohmite pot/speed control for small AC motors. They came in 120 & 240 volt models. Had a trim pot to adjust low speed.. We used to cut a 1/4" thick aluminum plate 3.5 by 3.5" and mount it to cover of a 1900 box. Still use one for an old single speed hand drill. Tried to purchase some for a job a few years ago but Ohmite discontinued the models that I had. Never had trouble with either a 5 or 10 turn pot. Had 3 to 10 HP analog drives ( used a pots for about 6 seperate settings that ran 3 conveyors for newspaper. No matter who calibrated critical ramp up speed after pots got warm after running say halve a hour one conveyor would have a slow start up causing major paper jams. Tech from company say they should have used far superior digital drives.

 

[RumRunner]

Thanks everybody I have found the sweet spot with the new Pot 1k 1 turn from mc master carr p/n 7436k37 works very well ,though out the whole entire range .

We should reciprocate the gratitude. . ..as mentioned by another member.
If those visitors would only follow up throughout his troubleshooting ordeal--everyone benefits.

It doesn't matter whether he achieved success or not from all the suggestion/recommendation-- you offered a sense of accomplishment.

Thank you again--you set a good example.