Current regulator IC adjustable with linear potentiometer
I've been struggling to find a schematic, or simulate myself, of a way to regulate current, down to say 10mA, with LM317 with a linear potentiometer, and it doesn't seem to possible. Best I've been able to find is a way to do it down to ~100mA linearly (with big ass power resistors too).
Which makes me think I'm not using the right IC - are there any current regulator ICs (up to say 30v) that were designed with potentiometer adjustment in mind?
The reason for the linear requirement is to be able to label the pot with easily discernible limit levels.
Posted Oct 4, 2018, 7:18 PM UTC
432
op-amp and transistor, make whatever you like
Too advanced for me at this point.
Nah you'd be surprised.. Your LM317 is basically just an op-amp and transistor (and 1.25v reference) already except you can't get inside there and change the arrangement or the reference voltage.
There's two ingredients:
Op-amp (with negative feedback) will generate whatever output voltage that makes both its inputs the same voltage - that's basically all you need to know until you get to very advanced op-amp usage.
Transistor (of any type) just acts as a voltage-to-current converter.
So now you have 1) a thing that makes two voltages the same and 2) a thing that controls current based on voltage.
This is literally all you need for a huge number of various tasks..
Voltage regulator? change current so the output voltage matches a reference.
Current regulator? change current so the voltage developed by a sense resistor matches a reference
Differential amplifier? change output voltage to be
Vin1 - Vin2by simply comparing vin1-vout with vin2/2Boost converter? turn on when output voltage is too low, turn off when inductor current is too high.
Buck converter? turn on when output voltage is too low. turn off when output voltage is too high.
Arc welder? constant current regulator that makes big voltage spikes when the load resistance resembles infinity.
LED brightness controller? Just a current regulator
Battery charger? Also just a current regulator, but turns off when the voltage reaches some threshold.
IR photodiode amplifier? keep voltage at zero by feeding current through a resistor, so output voltage is proportional to photons per second.
Audio amplifier? make output voltage some multiple of input using a resistor divider, and add a crapton of current gain with big discrete transistors on a big heatsink
and tons of other stuff
It sure as heck not. And if it is, time to git gud.
The question is: do you need current limiting (avoid frying shit if you short it) or an actual current source (a constant voltage is not important at all)?
primarily i'd like to avoid frying the parts that comprise my shitty circuits
i'll have an lt3080 for the constant voltage afterwards
https://electronics.stackexchange.com/questions/215418/smartest-way-to-use-current-limit-using-lm317
Current limiting is not the least complex things around, my dude.