Hi, Hello to all,
New member here and noob in the world of microcontrollers. My wife just purchased a beginner Pottery Wheel. Good news is that it's powered with a decent 450W brushless motor that runs very quietly and all that power is in fact delivered to the wheel head. The bad news is that the included foot pedal speed control is crap. Inside the plasticky two part foot pedal I found only one rotary potentiometer in total. That would be acceptable for a discounted beginner tool if it does the job. Problem is that. almost 90% of the speed of the wheel is attained by the first 10% of the rotary pot rotation. That makes the pottery wheel unusable.
Is it possible to replace the existing rotary potentiometer ( B4.7K - WTH118-2W ) to a better suited item to be able to distribute the speed selection across a much wider range?

 

My quick Google search indicates that it's a linear taper potentiometer, which is not what I expected to find based on what you're seeing. You may have better results with a log (audio) taper. Find one with the same physical package, resistance range, and watt rating and see if it helps.

 

My quick Google search indicates that it's a linear taper potentiometer, which is not what I expected to find based on what you're seeing. You may have better results with a log (audio) taper. Find one with the same physical package, resistance range, and watt rating and see if it helps.

Thank you for pointing to that direction. I'll report back the results.

 

As it is a taper potentiometer, could it be that it has just been wired incorrectly?

 

As it is a taper potentiometer, could it be that it has just been wired incorrectly?

That was my initial assumption. Changing the connections points just flipped speed control and kept the " jumpy-ness " misbehaviour. I think the PWM inside the motion control board was designed to work with another device. They just repurposed the mainboard and ditched the other for a cheap potentiometer solution to save a buck or two.

 

That was my initial assumption. Changing the connections points just flipped speed control and kept the " jumpy-ness " misbehaviour. I think the PWM inside the motion control board was designed to work with another device. They just repurposed the mainboard and ditched the other for a cheap potentiometer solution to save a buck or two.

Can you measure the pot to make sure it's really a log? Do you have a part number for the PCB?

 

The pot appears to be a linear 5Kohm. It actually reads 5.23Kohm across the terminals and the wiper changes the resistance quite linearly from a minimum of 7 ohm all the way to maximum of 5.23Kohm. I have not opened the sealed plastic casing holding the the controller. The normal pottery work creates a lot of water splashes and wet clay slips go everywhere. I will open that sealed case if I really have to. The manufacturer parts-sheets are non existent. I am not surprised because even the high end pottery wheel manufacturers don't share trade secrets about their controllers.

 

The pot appears to be a linear 5Kohm. It actually reads 5.23Kohm across the terminals and the wiper changes the resistance quite linearly from a minimum of 7 ohm all the way to maximum of 5.23Kohm. I have not opened the sealed plastic casing holding the the controller. The normal pottery work creates a lot of water splashes and wet clay slips go everywhere. I will open that sealed case if I really have to. The manufacturer parts-sheets are non existent. I am not surprised because even the high end pottery wheel manufacturers don't share trade secrets about their controllers.

Change the pot to a log or anti-log depending on the resting state and problem solved.

 

Change the pot to a log or anti-log depending on the resting state and problem solved.

Yes, joseph_e2 also suggested a log potentiometer. I couldn't find one within the same range of specs and physical package size on Amazon. So, just for a quick test I purchased a sliding version. It should arrive on Monday.

 

Yes, joseph_e2 also suggested a log potentiometer. I couldn't find one within the same range of specs and physical package size on Amazon. So, just for a quick test I purchased a sliding version. It should arrive on Monday.

Please don't buy fake parts on amazon. Newark, Digikey and Mouser all have good parametric search.

 

Found it on Digikey. I hope it's ok to post the item here:

KA5021S28-ND KA5021S28 Precision Electronics Corporation POT 5K OHM 2W CARBON LOGARITHMIC

 

Found it on Digikey. I hope it's ok to post the item here:

KA5021S28-ND KA5021S28 Precision Electronics Corporation POT 5K OHM 2W CARBON LOGARITHMIC

If the shaft matches the original you should be ok.

 

Hi, Hello to all,
New member here and noob in the world of microcontrollers. My wife just purchased a beginner Pottery Wheel. Good news is that it's powered with a decent 450W brushless motor that runs very quietly and all that power is in fact delivered to the wheel head. The bad news is that the included foot pedal speed control is crap. Inside the plasticky two part foot pedal I found only one rotary potentiometer in total. That would be acceptable for a discounted beginner tool if it does the job. Problem is that. almost 90% of the speed of the wheel is attained by the first 10% of the rotary pot rotation. That makes the pottery wheel unusable.
Is it possible to replace the existing rotary potentiometer ( B4.7K - WTH118-2W ) to a better suited item to be able to distribute the speed selection across a much wider range?

The test sliding log potentiometer arrived and installed. It works perfectly - almost. The 10K log slider pot starts to turn the wheel-head so ever gently and quietly yet with full torque ( assumption only ) at about half its travel range. The maximum speed ( assumption ) is set towards the end of slider's travel range with enough extra travel to give assurances for not missing any available speed up at that end.
I purchased the replacement rotary log version from digikey immediately.
Thank you all for your help to solve this controller issue.

 

The test sliding log potentiometer arrived and installed. It works perfectly - almost. The 10K log slider pot starts to turn the wheel-head so ever gently and quietly yet with full torque ( assumption only ) at about half its travel range. The maximum speed ( assumption ) is set towards the end of slider's travel range with enough extra travel to give assurances for not missing any available speed up at that end.
I purchased the replacement rotary log version from digikey immediately.
Thank you all for your help to solve this controller issue.

Excellent.