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I have a power supply unit with adjustable output voltage. The output voltage is adjusted using a potentiometer. However, I need to change output voltage remotely and dynamically.

What kind of circuit should I use to substitute the potentiometer in the power supply unit to control it remotely (30-50 cm) by the micro-controller?

Both analog and digital control of the modified PSU is acceptable. Cost and low wire count are also important factors. However, the most important factor is how reliable the system is (isolation between PSU and MCU in case of a lightning strike etc).

Thank you in advance.

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    \$\begingroup\$ A digital pot comes to mind, but without a schematic of the power supply. ... \$\endgroup\$ – Passerby May 1 '15 at 13:48
  • \$\begingroup\$ @Passerby, the problem I see with the digital potentiometer is that it requires 4 wires (power + i2c bus) from MCU to the PSU. \$\endgroup\$ – Konstantin May 1 '15 at 14:05
  • \$\begingroup\$ Unless you go wireless, any solution will require wires. At least data and common ground. There are 1-wire digital pot as well. \$\endgroup\$ – Passerby May 1 '15 at 14:17
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Here is one approach that might be suitable as is or with slight modification.

PWM controlled divider

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  • \$\begingroup\$ thank you for the reply. In my case, output voltage will be in range 40-60V. It seems that with your approach I need to bring VCC power from the MCU board? \$\endgroup\$ – Konstantin May 2 '15 at 20:32
  • \$\begingroup\$ You said you are using a potentiometer now, right? But you just want to make it remote? All of the circuitry above can be placed near the equipment under test, and VCC can be the same voltage you are currently using for your potentiometer. Just make sure that Q1 is rated to 60V or more to be safe. Only the PWM signal and GND need to come from the MCU board. Maybe there is something I am not getting about your setup. \$\endgroup\$ – mkeith May 2 '15 at 21:42

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