I'm planning to build an aquarium lightning system with individually controllable LED's, I don't have much experience with electronics except from the irregular tinkering, but I'm a programmer and I think I'll be able to put something decent together.
The system will consist of about 30 * 3W LEDs, I already have those as well as heat-sinks, lenses, thermal glue and a couple of PWM-boards similar to this. My initial plan was to build some kind of simple transistor switch between each individual LED and the power supply, a switch that I could control with the PWM-board, which in itself is controlled by an arduinio/raspberry pi.
Then I read on and discovered that LEDs are supposed to be current regulated, not voltage regulated. So now I'm not sure about how to move on.
I've considered just buying a bunch of individual constant current drivers like these, but I don't see how I'd be able to pwm those properly. (I realized that most of my LEDs aqually are in the 700mA range instead of the 300mA that I first thought, now it's starting to get unreasonable expensive to buy one of these for each single LED, in an otherwise quite cheap system...)
What I really would need is some kind of variable current driver, from between 0(?)-800mA (I've understood that very dimmed LEDs draws very little current, so I need a big range there), that I can control with pwm, but that does not seem to be a thing I can buy like the regular constant current circuits.
Any ideas? I've considered to buy a current sensor for each LED and to use this data to properly modulate the individual LED's myself. But I'm not sure I can find some that reliably can measure the low currents that I need. Or does the spec sheet for that MAX471-chip really say that it has a resolution of 0.5 mA per A (Current-Sense Ratio)?
Clarification on functional needs
- I need a lot of light in order for the plants in the aquarium to thrive. I need as much white light as I can get from each watt.
- I want to be able to control the light in aspect of intensity as well as tone/temperature (I have different temperature LED's).
- I want to be able to control exactly what parts of the tank are lit and how those parts are lit. E.g., I want to able to simulate similar dynamics as to clouds passing by or lightning, or just to selectively light certain parts of the landscape.
- Not critical but valuable: Scalability. The ability to easily to add or remove LEDs.