I am somewhat confused on how the current limiter configuration works with the LM317. It's configuration looks as so:
Datasheet: http://www.ti.com/lit/ds/snvs774l/snvs774l.pdf
The formula given is \$I_{out} = \frac{V_{red}}{R1}\$, and the constraints work, because 0.8 Ohms is roughly the minimum load requirement, and 120 is the upper limit of what it can supply (~1.5A)
My issue now, I wish for it to be controlled by a microcontroller via an optical encoder.
- A digital potentiometer at least from what I have seen can only pass ~40mA current through it, so that is out of the question
- I wish for a very dynamic range, so transistors switching power resistors by uC is not very allowing.
The only thing left I can think about is driving the ADJ pin with the uC, and try to figure out what on earth R1 does to it.
I assume the wire going to ADJ is just to create a path, and Vref (1.25) is otuput in Vout? and V/R1=I passing to Iout. I am not sure how that helps me, as I am left with only 1.25V.
What happens in this schematic? What can I feed ADJ in place of R1, assuming I have a sense resistor that knows the current going through the circuit?