Path: utzoo!attcan!uunet!cs.utexas.edu!sun-barr!rutgers!cmcl2!phri!roy From: roy@phri.nyu.edu (Roy Smith) Newsgroups: sci.electronics Subject: Re: Blue LED Message-ID: <1990Nov5.172318.1487@phri.nyu.edu> Date: 5 Nov 90 17:23:18 GMT References: <1990Nov2.171429.28170@syssoft.com> Sender: news@phri.nyu.edu (News System) Organization: Public Health Research Institute, New York City Lines: 31 tom@syssoft.com (Rodentia) writes: > Anyone making a tricolor LED yet? fng@questor.wimsey.bc.ca (Felix Ng) replies: > I think Radio Shack sells one. Red and green with DC and yellow with AC. I think Rodentia (presumably not tom@syssoft.com's real name) meant an LED with all three primaries, i.e. red, blue, and green that you could mix anyway that you like. The red/green/yellow LEDs are just a red and a green LED back-to-back. One polarity lights one, the other polarity lights the other, and AC lights them both, a half-cycle each. I could see packaging all three in one plastic case, but I don't see how you make it work with only 2 pins. The minimum pin count I could see is 3, with the 3 LEDs delta connected, allowing you to light any one or two at a time. If you wanted to light all three at once, you would need 4 pins; an anode for each and common cathodes (or the other way around, if you prefer). It would certainly be a heck of a lot simplier that getting the odd bipolar voltages you'd need in the delta connection. tom@syssoft.com (Rodentia) again: > how would power consumpion compare to LCD shutter solutions? My latest Digi-Key catalog shows most of the LEDs drawing 70-90 mW. Even for a modest resolution 512 x 512 display at 70mW/pixel, you'd be drawing 18 kW! Hardly low power. -- Roy Smith, Public Health Research Institute 455 First Avenue, New York, NY 10016 roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy "Arcane? Did you say arcane? It wouldn't be Unix if it wasn't arcane!"