I mean using fixed voltage not current.=20 ________________________________ From: Andre Abelian To: Microcontroller discussion list - Public. Sent: Wed, March 2, 2011 9:28:02 AM Subject: Re: [EE] 12V flexible LED strings for automotive use as daytime ru= nning=20 lights Patrick, The reason leds are failing or you see discoloration because of led resista= nce=20 is dynamic it changes right after turning it on (+ outside temp) and by applying fixed current led life= =20 becomes shorter. the best way to use leds for lighting is by using constant current not volt= age. Andre=20 ________________________________ From: Patrick Moody To: Microcontroller discussion list - Public. Sent: Wed, March 2, 2011 8:59:48 AM Subject: [EE] 12V flexible LED strings for automotive use as daytime runnin= g=20 lights I have been using these (ebay link - http://bit.ly/hbiCF0 ) LED strings as additional lighting for the front of my motorcycle for the past 3 years. I was looking for something to make me more obviously visible to oncoming traffic in an attempt to reduce my likelihood of having someone in pull out in front of me because they didn't see me and when they do, to make sure they have absolutely no excuse. Of all the options I've found so far these seemed the best because they don't require any modification to be run from the 12V supply on the bike, they are water-resistant due to the rubber moulding, they are flexible so can be formed to the shape of the internal fairing around the front wheel where I have them mounted, and because they have a rectangular shape allowing them to be mounted with the lights pointing along the tangent of the surface where they are mounted. The only similar products I have found are flatter strips with the lights facing normal to the mounting surface which therefore don't suit my application. I want them facing forward towards the oncoming traffic rather than inwards to the front wheel. A holiday photo (800x600 jpg) showing what this looks like: http://bit.ly/e= 4L5ur The problem is that after about a year they begin to lose brightness and the flexible circuit seems to deteriorate so that some of the LEDs (usually in groups of 3) begin to fail (as those with keen eyes might spot in my picture). Having replaced a set on one side of the machine which had failed, it was quite noticeable that the new set were brighter than the old set. Perhaps the lesson to learn is to always replace the whole lot at once but I'd rather find an alternative that won't need replacing in the first place. In summary I'm looking for: Strings of white LEDs in a clear flexible waterproof housing Run directly on 12V LEDs are spaced approximately 1cm apart along the string Can be mounted to face along tangent of mounting surface Longer mtbf (mean time before failure AND before fading) Better durability in automotive environment - vibration, moisture, heat and cold. Does anyone have any suggestions? Patrick --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist =20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist =20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .