Question on brightness units for LED's

[jhicks]

Hello,

I've been thinking over for some time about creating a programmable LED display. I have an EEPROM and microprocessor among other things already, so it's not like I'm buying all the parts. Ideally, this display would be viewable from up to 30-40 feet away so it will have license-plate-sized letters. I haven't found an LED display that doesn't already have programmable features in it already so I'm considering building one for myself (yes I know it's a lot of wiring!) but I'm very concerned about finding LED's that are bright enough and have a wide enough viewing angle.

I've looked around Ebay waiting for a good deal on a couple hundred LED's, but units such as "cd" are quite foreign to me and I have no idea how bright 1cd is. http://www.radioshack.com/product/i...&cp=&sr=1&kw=led&origkw=LED&parentPage=search this is 720mcd, but I've bought something like it before and there's no way it would be enough. I found a vendor selling around 100 LED's for 60 bucks that are rated at 100,000 mcd. Is that more appropriate? Thanks.

 

[mgb_phys]

Well 1 Candela is roughly candlelight!
I think you are going to have to do some experiments, it will depend on details of the viewing angle, alignment and lighting conditions - plus the fact that most of the super power LED specifications are lies ( or at least measurements made under rather optimal conditions).