siggy Posted October 5, 2005 Share Posted October 5, 2005 Ok I've got 3 leds and I've tested them with a 3V battery and got two greens and a red led. LEDS are rated for 24V. Okay just tested them in the landy and got three red LEDS? Whats going on? surely a red LEDS is a red LED? or can they change colour with varying voltage? Quote Link to comment Share on other sites More sharing options...
02GF74 Posted October 5, 2005 Share Posted October 5, 2005 The physics behind a LED means they emit light in a specific frequency range, i.e. colour if in the visible spectrum. Changing the voltage will change the intensity but not the colour. A recent innovation in LED technology (well within last 5 years!) is two different coloured LEDs in the same package, usually identified by having 3 leads (bi-colour). By altering the voltage to either LED, a variety of colours can be produced. Also the human eye can be fooled into seeing different colours when the light is intensely bright. Unless you are colour blind, have fitted a different set of LEDs to the ones you tested or wired up the wrong two leads pins in a 3 lead bi-colour LED I can provide no explanation for the phenomenum you are witnessing and suggest you contact the Guinness book of records pronto. Quote Link to comment Share on other sites More sharing options...
siggy Posted October 5, 2005 Author Share Posted October 5, 2005 They've only got 2 legs and I have only 3 leds (got them from work), we use white, red or green LEDS these weren't labeled so didn't know what they were (colour wise). And no I'm not colour blind couldn't do the job I'm doing if I was. Also I knew about the intensity bit with the current. They also worked fitted one way round (like the standard ones)! Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted October 5, 2005 Share Posted October 5, 2005 It be the work of the Devil I tell ye ! Mo Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 5, 2005 Share Posted October 5, 2005 There are bi-colour LED's that swap from green to red if you reverse the voltage, my money's on that. Better test all of them to be sure! 02GF74 - bi- and tri-colour LED's have been around for yonks, the latest load of really useful super-bright multi-colour ones are a recent thing using matched LED's on one chip to be able to make a decent range of colours, those tend to have more than three legs. The three legged ones are usually red/green with a common negative leg and give a rough approximation of orange if you power up both sides at once. There are other colour combos available but they're not cheap for what they are so not very common. Edit #2 to add the super bright new generation types are here: www.lumileds.com and have been in use for stage lighting for a number of years now. Quote Link to comment Share on other sites More sharing options...
siggy Posted October 6, 2005 Author Share Posted October 6, 2005 Well stuck them on battery one way green reversed them nothing stuck them in car red reversed them nothing now absolutely NOTHING I think I melted them Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 6, 2005 Share Posted October 6, 2005 Hmmm, are you sure they're 24v LED's with their own internal current limiting resistor and not, for example, normal LED's that (at work) are used with an external current limiting resistor? LED's do go funny colours when tortured, although they never do it for very long Quote Link to comment Share on other sites More sharing options...
siggy Posted October 6, 2005 Author Share Posted October 6, 2005 Yes definately 24V LEDS they are used for signallers panel indications. It a possibility then don't have and internal resistor. Possibly a reason why they weren't labelled as they are the wronguns for work Quote Link to comment Share on other sites More sharing options...
Neil Marshall Posted October 6, 2005 Share Posted October 6, 2005 now absolutely NOTHING I think I melted them That's what friends are for......... Neil Quote Link to comment Share on other sites More sharing options...
BogMonster Posted October 6, 2005 Share Posted October 6, 2005 Witchcraft I reckon. I suggest you hit them repeatedly with a hammer Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 6, 2005 Share Posted October 6, 2005 Siggy - if it helps ease the heartbreak of losing 3 LED's I can post you 3 more, with resistors soldered on and the + and - terminals clearly marked Quote Link to comment Share on other sites More sharing options...
siggy Posted October 6, 2005 Author Share Posted October 6, 2005 I had hoped to make the indicators on the dash flash brighter but until I can find some ultra bright LEDS I'll give it a miss I have pm'd simonb about his dash LEDS but thanks for the offer Quote Link to comment Share on other sites More sharing options...
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