How to switch the power of groups of 3W LEDs

Dear friends,

I've been looking for a way to efficiently drive as well as switch a matrix of about a few hundred watts worth of high powered colored LEDs. I will be using several different wavelength LED's that are grouped. In the end, I want to be able to switch on and off each single wavelength.

  • 630nm 6 x 10pcs - RED
  • 660nm 3 x 10pcs - FAR RED
  • 470nm 1 x 10pcs - BLUE
  • 450nm 1 x 10pcs - DEEP BLUE
  • 610nm 1 x 6pcs - ORANGE
  • 380nm 1 x 2pcs - ULTRA VIOLET
  • 850nm 1 x 2pcs - INFRA RED
  • and 1x 2 pcs - COOL WHITE

I want to test a spectroscopic approach to long-term time-lapse monitoring of plants growing under artificial lighting conditions: A camera will be installed above the plants, and shoot a series of pictures in specific time intervals. For each time interval, the system will acquire one picture per wavelength used. In post-processing, I want to combine the images to a faux-color image to highlight differences and changes in color of leaves over time. (This will be the actual subject of the research.)

As this is a research project I can use power from the electric grid of the lab, but eventually alternative sources of power are supposed to be used. Also, I want to at least approximately be able to restrict/control the amount of waste-heat generated by the system, since I have to account for all energy being put in and removed from my model space.

To my knowledge, similar needs arise for the cultivation of medical cannabis, so this is where I got most of my practical advice from so far. I assume the mix of wavelengths that is used in these projects will be sufficient for my project as the absorption spectra of chlorophyll should be approximately equal across plants. However, there, switching of LEDs is rarely a concern, they usually just blast as much light as needed on the plants.

Research budget, as always, is an issue, so I need the most cost effective solution.

A couple of questions:

Does it make more sense to give each LED its own driver?
I'm afraid that if I use one driver for a whole group and a single LED burns out, it might either a) damage the other LEDs due to overcurrent or b) if the whole group of LEDs goes out it will compromise the experiment.

Can I simply control the LED's independently by switching each driver with a MOSFET?

Can I use a PC PSU for supplying 12V to the constant current drivers?

" high powered colored LEDs" need constant current drivers to keep them from burning out.
You can wire them in series if your source voltage supports that, or wire them individually.
Take a look at some of the parts here for example. If you look at their datasheets, you will notice they are similar to switching voltage regulators - only in this case they are controlling the current out instead of the voltage out.
http://www.digikey.com/product-search/en/integrated-circuits-ics/pmic-led-drivers/2556628?k=led+driver&k=&pkeyword=led+driver&pv87=2&pv494=24&FV=fff40027%2Cfff802d4&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

If you are using a 12V source, then you can probably control the LEDs in groups of 3.
If "high power" is less than 1A, then you can use the filter tools here and perhaps find a part that can drive more than 1 output string:
http://www.digikey.com/product-search/en/integrated-circuits-ics/pmic-led-drivers/2556628?k=led+driver&k=&pkeyword=led+driver&FV=fff40027%2Cfff802d4&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

3W LEDs, that implies something like these
http://www.allelectronics.com/category/340060/leds/3w-leds/1.html
which are 700mA, with up to 2.3 to 3.4V max Vf, so strings of 4 and 3 LEDs from 12V would work.
Cooling will have to be accounted for, for sure.
This video goes into things nicely. The part used may be overkill if you have a regulated voltage source

Thanks a lot for looking these up for me, that's extremely helpful!