Potentiometer Upgrade from Cohesion3D

Machine: K40

Board: Cohesion3D

Firmware: _Smoothie

Problem/ Question: I’m in the process of changing the potentiometer but I think my wiring is wrong. The images here are of the original. (Flat wide from left to right GWB) The next is the replacement (blue) and how I have it set at the moment. It doesn’t seem to be adjusting the amount of output. The meter on the machine says 0 at the total 0 position but as soon as i dial up (clockwise) the meter jumps to 10ma. Before I burn out my laser, please advise. I have included a close-up of the Pot as well. Forgive the soldering job but at this point, they are temporary for testing purposes.

This last picture is a closeup and a flip 180 degrees so the Pot can be read.

Black where white is and white where black is

Thank you. I did do that but it’s possible the pot is bad because it is not adjusting the power prperly. I can go counter clockwise and limit id down and get nothing (as it should) but as soon as I move is clockwise a tiny bit, it jumps to 3mA on the meter then stays there as I rotate clockwise several times and max limit it and it pins the needle to the max mA it will read. Not sure if it’s a bad pot or not but I had to go back to the original for now. Thanks for the advice!

Hi Adam,

On this potentiometer model, the wiper is the far left pin (2) instead of in the middle. If turning the knob clockwise lowers instead of raises the current, you’ll need to switch the wires on pins 5V (1) and G (3). It sounds like you’ve tried this, which is great.

Put the probes of your multimeter red to 5V (pin 1) and black to G (pin 3).

It should read within a few ohms of the rated resistance of your potentiometer. (Note: If you get a different reading, one of your probes is on the wiper. Try different combinations of two probes until you get one that gives you the right reading. You now have the probes on the ends.)

Turn the controller from one side all the way to the other while keeping the probes in contact with the ends. The resistance should either not change at all or change only very slightly from one side to the other.

Take one of the probes off one of the ends and put it on the wiper. Slowly turn the knob all the way from one end to the other while watching the multimeter. At one end, it should have a resistance of only a few ohms. At the other end, it should have the maximum resistance. It should slowly and continually decrease/increase as you turn the knob with no sudden jumps.

Please let us know the results of your tests.

Thanks for the directions. I have done as you suggested. A few things jump out at me. It seems that this pot takes MULTIPLE rotations to come to a stop. From counterclockwise total stop to clockwise total stop. Probably 15-20 total 360 degree rotations. Which seems excessive. Total zero at counterclockwise ranging with no increase around 3mA until total stop clockwise. And it jumps and max out the mA meter. I think the pot is defective. It should gradually increase. This does not.

Thanks for the additional information, Adam. Please fill out the contact form on our site with the order info and a link to this thread so that we can arrange a resolution.

Thank you!

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