Potentiometer

[David NobleParticipant @davidnoble71990]

I have a stepper motor driving the X axis on my mill. The speed is adjusted with a potentiometer. All of the adjustment that I use is located on the first quarter of the dial. Is it possible to use a different pot’ which will give me more accurate control over that first quarter?

Many thanks, David

[David NobleParticipant @davidnoble71990]

[Grindstone CowboyParticipant @grindstonecowboy]

I don't see why not. I would use a lower resistance pot plus a fixed resistor to make the total resistance value equal to that which you currently have e.g. if it's a 1k pot at the moment, get a 250 ohm pot and a 750 ohm resistor on one side or the other (determine which side by trial and error or by working out which quarter of the range you are using now).

That should work

Rob

Edited for spelling mistooks

Edited By Grindstone Cowboy on 14/03/2023 23:20:02

[not done it yetParticipant @notdoneityet]

Is it a logarithmic pot? Possibly changing to a linear device might help, if it is?

[Robert Atkinson 2Participant @robertatkinson2]

This is possible but there may be better ways. Are there settings on the stepper driver? what does the manual say?

Information on the unit is use would help. As a minimum, does the control have 2 or 3 connections? what value is it?

Robert.

[Les Jones 1Participant @lesjones1]

The schematic of the oscillator that you are using to generate the step pulses would help us with suggestions.

Les.

[David NobleParticipant @davidnoble71990]

Posted by Grindstone Cowboy on 14/03/2023 23:18:58:

I don't see why not. I would use a lower resistance pot plus a fixed resistor to make the total resistance value equal to that which you currently have e.g. if it's a 1k pot at the moment, get a 250 ohm pot and a 750 ohm resistor on one side or the other (determine which side by trial and error or by working out which quarter of the range you are using now).

That should work

Rob

That's exactly what I needed to know, Thank you Rob.

[David NobleParticipant @davidnoble71990]

Posted by not done it yet on 15/03/2023 07:47:40:

Is it a logarithmic pot? Possibly changing to a linear device might help, if it is?

I didnt know about linear pots, I'll have a look, Thank You.

Thank you Robert, The unit is a bought in device as a bolt-on addition to my mill so I didn't get a manual for the driver.

Thank you Les, Whoa!!! as you may have deduced my skill set is not in electronics.

David

[SillyOldDufferModerator @sillyoldduffer]

Ummm, is the pot connected to the correct source voltage?

Usually speed control pots are hung across a supply rail, typically between ground and +5V, provided specifically to put the correct maximum voltage on the controller. In my example, full left is stop (0V on the wiper), and full right is full-speed ahead (5V on the wiper). Putting more than maximum volts on the wiper won't make the motor go faster, and risks blowing up the electronics.

Wiring mistakes are possible because some controllers have terminals with other voltages on them, such as 12v or 24V.

David's ground and wiper must be connected correctly because turning the pot controls speed, hurrah – it's not far wrong! However, is it possible the third pot wire is connected to the wrong terminal on the controller? If so, an easier fix than adding a resistor.

Dave

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