using PWM signals to control variable power supply.

[TechJunkie97]

I have a DIY 0-30v 0-3amp power supply with 10k potentiometers to control the voltage and current with voltage dividers from 0 to 10v. I am planning to use the chip from Arduino Uno ( Atmel atmega328p ) for driving these voltages. The circuit diagram of the power supply is attached below.

The power supply has 24v for a fan but I do not intend to cross 1 amp so I don't need a fan. I am describing a couple of options that I came up with:

OPTION 1:
Use 8705 regulator to drop down from 24v to 5v for chip operation and use that 24v supply again to power op-amp for converting the signal from 0-5v to 0-10v. Please see the attached circuit diagram for more details.

OPTION 2:
Use USB cable to power the chip and 24v from power supply for powering the op-amp for converting 0-5v signal to 0-10v

OPTION 3:
Use a 9v volt battery for the op-amp. Use 5V regulator to drop voltage for the chip, however, the max op-amp voltage will be less than 9V. I think this option prevents heat losses but also sacrifices some output voltage


All my knowledge here is solely from Dave's videos and I have never used a voltage regulator or op-amp before. So, please point out if anything is wrong. I would like to know your opinion about which option seems most reasonable or if there is a better approach to this problem. Also, do I have to worry about limiting current in these circuits?