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MAKE 2008 Grow LEDs Array Prototype Design
Single sided board design for an array of 24 blue, 24 red, and 2 white LED. For use as small plant lighting. Switching (SMPS) power supply and optional digital control unit are external, and support a minimum of 2 arrays. The white LED are switched with a latching button. Series strings of LED are brightness regulated using MMBT3906 based current sources for immunity to poorly matched Vf and variable supply voltages, 8 blue LED and 6 red LED per string. This setup will be powered by 24V rails, to provide headroom for the LED strings at Vf(max) and and 1V needed by the current regulators. A control unit will modulate power with PWM switching at greater than 200Hz, and be capable of simulating day/night cycles, movement of the sun from horizon to horizon, and adjusting the red and blue light balance.
Posted by rmrubin 
March 2008