Instructables

Step 6: Update! thigns have grown.

Picture of Update! thigns have grown.
Below is a photo of a little spinach sprout that has been germinated and grown a few leaves using the LED lights.

Having sprouted a few plants using this system i have transplanted them over to some compost on my windowsill as I didn't think my bench top supply would be too happy running 24/7.

I've picked up some odds and ends today now my student loan has come through, so hopefully within the next few weeks I'll have a larger system set up with 3w LED's and some nice microcontroller control, and quite possibly an instructable documenting it all.
 
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hjenkins4 years ago
LEDs are current controlled devices.  They are better driven by a current source than a voltage power supply.  Most supplys allow you to go into  current control mode by used the current limiter control.  Typically set the current at the recommended value for optimum life and longevity.  Now the reason why you would want to do this is to delete the series resistor, its not needed anymore.
And that greatly increases the efficiency.  On the other hand the LED's don't
use much power anyway.  But all the power in the resistor is lost unless you
use it to heat the little greenhouse you grow in.  But I think you'll get enough heat from the LED's that you won't need the heat from the resistor.  One other comment, the Blue LED is probably a different current rating than the other ones.