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I wish to remove 2 resistors in power supply unit and put variable resistors that would be controlled by my microcontroller.

  • 1st resistor should be in range of 3000-6000 Ohm
  • 2nd resistor should be in range of 0-200 Ohm

I am not very familiar with power supply I wish to tune and I guess I can use a set of relays to switch resistors.

I also saw some amateur radio have stepper drivers that rotate variable capacitors. May be it is possible to rotate variable resistors.

I guess if I knew that one pin of resistor is ground then I could use transitors instead of relays but it seems it is more complicated scheme with feedback OpAmp.

It seems to be complicated and possibly there is some chip that I can use to switch resistors from a range like 74HC4067 ?

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    \$\begingroup\$ Maybe look into "Digital Potentiometers", I think this is the module that you need for your application. Do you need the MCU to be isolated from the resistor you are trying to "control"? \$\endgroup\$
    – thisjt
    Oct 19 at 12:28
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    \$\begingroup\$ Perhaps you are trying to replace the function that the resistors used to do. i.e, were they providing a variable voltage source that you can digitally provide instead ? \$\endgroup\$ Oct 19 at 12:33
  • \$\begingroup\$ Do you intend to use the Arduino-adjusted resistor to set a reference voltage in the power supply's circuitry? Or do you intend to split the out out voltage (I.e. create a voltage divider) to set your voltage from the power supply? \$\endgroup\$ Oct 19 at 12:36
  • \$\begingroup\$ There is probably a better way to do whatever you are trying to do \$\endgroup\$
    – user253751
    Oct 19 at 13:51
  • \$\begingroup\$ @thisjt I read about digital potentiometers and they have a lot of warning when it could be used. I have not designed power supply that I wish to modify. They are used in audio and they lower signal in range of Db and not in Ohm range. \$\endgroup\$
    – Zeta Doop
    Oct 19 at 20:28
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Motorised variable resistors do exist. They are used on some audio mixing desks, to allow the storage and recall of mixer settings.

But this seems like a really complex solution, when there's probably a much simpler one.

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