How do i use the Lm317 voltage regulator with arduino?
Wow. Your making us really guess here. Do you want to be able to use the arduino to adjust the LM317 output voltage?
This is a guess... and it's not clear what you want... so I won't actually try to explain how anything might be done... yet.
I am sorry. Yes i want to have the output voltage be changed based on commands from arduino.
Well, I'm drawing a blank here, lol.
The best I can think of at the moment for an arduino controlled voltage source is a DAC (Digital to Analog Converter) with some high powered FET on the output.
If you MUST use the 317, then add an RC smoothing circuit to a PWM pin and then to the ADJ pin, which is always 1.25v less than Vo. Then use an Analog pin to check your output V.
Or use a digital potentiometer controlled by the Arduino for the voltage adjust resistor.