Post by thread:[EE] I am stucked with led panel for outside door

I can't decide minmum mcd value of led for outside door display, and for sufficient brightness under sun light. Any one has experience with outside led panel? On ebay, I can buy 5000mcd led in big quantity and pay quite high price. I have some led on hand with only 5 mcd. Is 5 mcd enough? Another thing I found is color fliter film, takes important role in result of led display panel for outside door. How to choose color filter film? Besides color, any thing else are considered? BR,

I used LED's as RED/YEL and GREEN indicators on a police motorcycle. In order for the LEDs to be readable in the July Arizona sun, I had to use 5000mcd's. But at night, that intensity would blind the officer. I had to design a PWM scheme to control the LEDs that had a very broad range of intensity. You will need to make a series of critical tests to get it right. --Bob microsoftwarecontrol wrote: {Quote hidden}>I can't decide minmum mcd value of led for outside door >display, and for sufficient brightness under sun light. Any >one has experience with outside led panel? On ebay, I can >buy 5000mcd led in big quantity and pay quite high price. >I have some led on hand with only 5 mcd. Is 5 mcd enough? > >Another thing I found is color fliter film, takes important >role in result of led display panel for outside door. How to >choose color filter film? Besides color, any thing else are >considered? > >BR, > > -- Note: To protect our network, attachments must be sent to spam_OUTattachTakeThisOuTengineer.cotse.net . 1-866-263-5745 USA/Canada http://beam.to/azengineer

> On ebay, I can > buy 5000mcd led in big quantity and pay quite high price. Be careful with those ebay LEDs. Likely to be factory seconds, with low homogeneity and poor reliability. Good for cheap hobby projects, but I'd steer clear for anything someone will actually use over the long term, or where each LED is expected to be remotely similar to its neighbor in brightness. Mike H.

Mike Hord wrote: >>On ebay, I can >>buy 5000mcd led in big quantity and pay quite high price. >> >> > >Be careful with those ebay LEDs. Likely to be factory seconds, >with low homogeneity and poor reliability. Good for cheap hobby >projects, but I'd steer clear for anything someone will actually use >over the long term, or where each LED is expected to be remotely >similar to its neighbor in brightness. > >Mike H. > > Agreed. High quality, high intensity LEDs are available from Lumex. That's the only source I am aware of. EBay won't have any of those. --Bob -- Note: To protect our network, attachments must be sent to .....attachKILLspam@spam@engineer.cotse.net . 1-866-263-5745 USA/Canada http://beam.to/azengineer

Hmm, I was just looking at some 20.000 mcd white LCD's on offer there. Now I haven't seen anything with a similar output outside of Ebay. Could this be a bogus claim? as in: you will get 20.000 mcd but the LED will only last 5 seconds....? Michiel On 05 apr 2005, at 17:30, Mike Hord wrote: > Be careful with those ebay LEDs. Likely to be factory seconds, > with low homogeneity and poor reliability. Good for cheap hobby > projects, but I'd steer clear for anything someone will actually use > over the long term, or where each LED is expected to be remotely > similar to its neighbor in brightness.

> Hmm, I was just looking at some 20.000 mcd white LCD's on offer there. > Now I haven't seen anything with a similar output outside of Ebay. > Could this be a bogus claim? > as in: you will get 20.000 mcd but the LED will only last 5 > seconds....? > > Michiel Not quite 5 seconds, but yes, they probably are trading lifespan for higher numbers. Digikey has some that are rated for 11000 mcd, and I believe mcd ~ kI, so doubling the current doubles the output brightness. It doesn't LOOK twice as bright to us, I believe, because of how we interpret light (the same way 2x audio power doesn't sound 2x as loud), but it is. But an LED designed for 15 or 20 mA and run at 30 or 40 mA is going to have a shorter lifespan, especially if it's a factory spare that they didn't feel comfortable selling to a "real" customer. Mike H.

On Apr 6, 2005, at 12:27 AM, Michiel Boerman wrote: > I was just looking at some 20.000 mcd white LED's on [eBay.] Now I > haven't seen anything with a similar output outside of Ebay. Could this > be a bogus claim? It could be. It's more likely to be an optimistic rating ("max" value rather than typical from spreadsheet or "binned" values.) But then that's true of many of the hobbyist suppliers as well. A good source of info for white LEDs (especially) is the candlepower forums (flashlight afficianados) http://www.candlepowerforums.com and/or the LED museum http://ledmuseum.home.att.net/ledleft.htm Consensus there is that the major Hong Kong white LED suppliers are pretty good, with the ratings provided being no more optimistic than many other suppliers. (and in particular, someone has been selling 26C White leds that people are putting in their flashlights for noticeable improvements.) The prices are great and the dealers pretty reliable by most accounts... (though, of course, watch out for shipping surprises!) I wouldn't expect the chinese imports to be be less quality controlled than the average hobbyist vendor. If you can afford factory-fresh LEDs from major distributers, that's great. Otherwise, china seems like a reasonable alternative, and eBay looks like a surprisingly good marketplace. BillW