Grow LED Array Prototype Rev. 2

Button pinouts were mirrored. Both switch channels of the button were used in order to reduce single element through current. Single-sided routing was dropped in order to pass DRC at 20mil. No benefits of single sided besides challenge, as most fab houses do not seem to care. The higher resolution boards were difficult to toner etch properly with my level of skill. The lower resolution will allow for easier etching and milling with tools at hand. A pair of arrays will be made in each method, in order to compare milled and etched PCB technologies. Some LED pins must be soldered top side due to lack of through hole plating.

Posted by rmrubin Posted in: Electronics Comments Off March 2008

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 Posted in: Electronics Comments Off March 2008