What is it?

This qwiic-compatible current controller can be used to drive leds/laser diodes and various other loads. It maintains a set current through a given load, even if the load resistance or source voltage changes. It can be set from 0 to 950mA (with +/-1mA accuracy) and operate at up to 30V.

It consists of a feedback loop: A shunt resistor measures the current; an op amp compares this to the DAC and then adjusts the gate of the MOSFET accordingly. The MOSFET is essentially used as a variable resistor - as a result, it can get warm with high current.

If you set the onboard DAC to 100mV, for example. The rest of the circuit will aim to sink 100mA across the green terminals.

Note: Some assembly required - the mosfet needs to be soldered. The mosfet can be mounted to a heatsink when working with larger currents.

Why did you make it?

I made this because I found myself requiring a dimmable LED/laser power supply that is Arduino controlled. Off the shelf options mostly use PWM, which can cause a noticeable flicker in the light if not adequately filtered.

What makes it special?

This device produces very steady current with low EMI because it uses analog electronics rather than high frequency PWM. Two controllers can easily be daisy-chained.

Please see attached datasheet for more info. There is also a repository with example code for C++/MicroPython