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IndustryArena Forum > Machine Controllers Software and Solutions > PlanetCNC > Connecting spindle (PWM) output to mini lathe, MK3/4 board
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  1. #1
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    Question Connecting spindle (PWM) output to mini lathe, MK3/4 board

    Hi all,

    Last few weeks I've have been busy installing and wiring a PlanetCNC MK3/4 controller board to convert my mini lathe to CNC.
    It is a Optimum 180x300 like lathe (like many others) and it has a potentiometer to control the spindle speed manually.
    I would like to replace the potentiometer and control the spindle speed with a PWM output of the MK3/4.

    The potentiometer is generating a 0-10V signal. I tried to generate this signal by switching the 10V+ with an optocoupler(driven by the spindle output) with 40Hz and feeding it through a low-pass filter.
    Unfortunately this does not seem to work.

    How could I connect the MK3/4 to the potentiometer wires?
    There are quite some people who retrofitted these Chinese machines but I cant find how they managed to control the spindle .
    Hopefully you can give me some insight!

    Thanks in advance and kind regards,
    Patrick

  2. #2
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    Re: Connecting spindle (PWM) output to mini lathe, MK3/4 board


  3. #3
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    Re: Connecting spindle (PWM) output to mini lathe, MK3/4 board

    It looks like that board does the opposite of what is needed. You need a board to convert a PWM signal to an analog signal.

    Maybe this?
    https://cnc4pc.com/c41s-pwm-variable...rol-board.html

  4. #4
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    Re: Connecting spindle (PWM) output to mini lathe, MK3/4 board

    The potentiometer has 3 wires going to it. One is ground, one is voltage (probably 10VDC), the third wire is connected to the wiper of the Pot. As you turn the Pot from minimum to maximum the voltage on the wiper wire increases. When you connect your analog output from the board (PWM to Analog) you would connect it to the wiper wire. You will also need to disconnect the wiper wire from the Pot. If you don't disconnect the Pot, you may not be able to hold the correct voltage.

    You can also use a solid state relay to turn the power on/off to the motor.

  5. #5
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    Re: Connecting spindle (PWM) output to mini lathe, MK3/4 board

    Thanks for the help!
    I have ordered a board to convert PWM-> analog 0-10V.

    I'll let you know if it works!

  6. #6
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    Re: Connecting spindle (PWM) output to mini lathe, MK3/4 board

    Hi all,

    I didn't have time to work on the lathe for quite some time. But recently I finally found a chance to work on it again and solve the issue.
    At Homann designs I ordered the digispeed gx v3 and it work perfect. I can finally control the spindle in the right way.
    Thanks for all your help!

    https://www.homanndesigns.com/index....products_id=21

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