In basic projects, controlling LEDs and other current-driven devices with a PWM signal can work fine.However, there are disadvantages, and using a constant current source can be a much better solution.This Qwiic/Stemma QT compatible Current Controller uses a large MOSFET and a DAC in a feedback loop to provide a constant current flowing between the two screw terminals.
If you’re new to electronics, constant current sources can sometimes be tricky to understand.Unlike a constant voltage source (which we’re used to with things like power supplies, batteries and the like) which put out a variable current at a fixed voltage, constant current sources do the opposite.They will dynamically adjust the voltage across a device to ensure a certain current flows.
Of course, they also have a voltage limit (just like constant voltage devices have a current limit) meaning they can’t just infinitely push current through any impedance.But for devices that are current-driven like diodes of all kinds, constant current sources give you a fine level of control.They can eliminate the need for series resistors, too, which can reduce the heat generated.
Just remember, it all obeys Ohm’s law! Laser diodes in particular are better driven with a constant current source, as you can compensate for varying light output by adjusting the current through the device.This current source is adjustable in steps of 1mA, all the way up to 950mA.The circuit supports a maximum of 30V, so you can power quite a string of LEDs or lasers.
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