300mA+/-5%. Now, why on earth would I want to power my Arduino board using something
like this? Can anyone explain why my board would want to have a device trying to drive a
fixed 300mA current into it? Makes no sense, unless maybe the p/s were jiggered after the
fact.
You would never want to power an arduino board with a true constant current power supply. An arduino board with nothing wired to it's output pins or 5V or 3.3 pins draws only around 80ma, and a true CC power source would raise it's output voltage as high as it could trying to force 300ma into the arduino board, which would most likely burn up many components on the board due to the high voltage.
There are some Asian DC constant current LED driver modules designed to power 1 and 3 watt power leds that also have a TTL level input that allows for PWM control for the module effectively allowing a dimming function if one wants to use such a feature, or as a simple on/off control using an arduino digital output signal. However you have to look carefully at the maximum PWM frequency that is allowed for the specific CC drivers that have this extra feature.
Lefty