I have a computer power supply which outputs 24v constant and I want to be able to use a circuit that has just transistors, voltage regulators, and resistors, and capacitors, to be able to control the voltage using an arduino. Essentially, it is like a potentiometer based voltage regulator, but I want to use an arduino to control it electronically.
I do not have access to a digital potentiometer, so please don't suggest that.
Edit:
I want to be able to get the output voltage anywhere between 0 and 24 volts with .1v steps.
The way I see it you have 2 options for creating an analogue voltage to use to control the power supply (for that is probably the easiest way to set a voltage).
You don't mention capacitors in your list of components... if you include capacitors you can create a low-pass filter on a PWM signal to generate a voltage which you can essentially "amplify" using the transistors.
Alternatively, you could use just resistors and 8 IO pins to create an R-2R ladder to give an 8-bit resolution voltage output.
Then it's "just" a case of creating a voltage controlled voltage regulator.
I like the low pass filter idea. Should I then wire it like such?
Arduino analog out -> capacitor -> transistor Base
Transistor Emmiter -> 24v supply
Transistor Collector -> Voltage out
Should I also stick a diode in there to prevent backfiring from the transtor to the arduino? Also, is a 500microF cap and a 2n2222 transistor ok? Im kinda new to the circuit world.
Edit:
Do I really need PWM since the arduino gives out voltages from 0-5v?
Why the restriction on what types of component you use? It will be a lot easier if you can use an op-amp (LM358 or similar) as well.
For the low pass filter, you need a resistor from the Arduino pin to a capacitor, other side of capacitor to ground. See attached. As it stands, this schematic is lacking short circuit protection, but that can easily be added.
If you can't use an op amp, you will need to make an amplifier from transistors etc. (not easy when you need the common mode voltage to include ground, unless you provide a negative supply as well). btw you haven't said how much current you need to provide to the load.
