LED brightness vs the Sun

[Kris01]

How much brightness will I need for a green 7-segment LED display to be readable in full sunlight? Is 10 mcd enough? What can I compare a candela to in the real world?

 

[MrAl]

Hi,

Just in case you dont get any other more educated responses...

You can order a small LED with a certain mcd range and lite it up with some current and take it to the place under the sun you want to be able to see the LEDs at. If it appears bright enough, you might go with that. If not, increase current and see if that helps, or try another LED. Sometimes nothing beats a good ol' fashioned test or two to make sure we are getting what we really want out of a circuit (or LED or other device).
Sorry i cant offer a more concrete idea, but i can tell you i had this problem myself and it isnt that easy to solve because sometimes the sun is so bright you really have to have a shade hood of some type. I ran into this problem when i replaced my "oil" light on my automobile with an LED. It was a high brightness LED, and driven at a healthy current level. Still, i have trouble seeing it if the car is parked in such a position as to allow the sunlight to directly penetrate the area where the LED is now located. It's plenty bright when the sun doesnt hit it directly, but other wise it's a bust.
In other words, sometimes you need a hood as well as a high brightness LED to be able to see the LED as well as you really would like to see it.

 

[SABorn]

The best solution is to add a filter lens to the face of the display, for interest if you have a red led display you use a red lens and for a green display you use a green lens.

Coloured acrylic plastic works very well, or another trick i often use is cellophane, a few layers works well, what i do is print a paper front label for my project and cut a window out where the display is, then tape several layers of cellophane over the back of the window cutout, then laminate the the whole label, trim it to size and you have a nice front label with a filter lens for the display.

Here is an example of the label.......

Pete.

 

[ericgibbs]

hi,
Some members have used 'toffee' wrapper coloured papers for single LED's, they claim good results and if it doesn't work as expected, you can always console yourself by eating the toffee's.

 

[Boncuk]

There are clocks indicating remainders of red, yellow and green phases of traffic lights digitally in Thailand at almost every road/street intersection.

I bet they don't use any filters, but instead use high brightness or super bright LEDs with a sunshade mounted on top of them.

There are also solar powered warning lights mounted along country roads flashing yellow or red, depending on right of way with no extra filter mounted, but they also have proper sunshades.

Using super bright LEDs and the proper shading will be an effective solution.

Boncuk

 

[carbonzit]

Well, you can speculate all you like, but as has been stated earlier, the proof is in the pudding, so to speak, so experimentation is in order here. Since the parts are relatively cheap, shouldn't be too big a deal.

 

[Kris01]

Thanks for the responses guys. Sounds like it's not a plug 'n play operation. I might just have to find the brightest ones that I can and play with the current if they end up being too bright. Can you recommend some bright green LEDs around 0.5" in size?

 

[Kris01]

Any problems with dropping the current to the LEDs to make them less bright (if I have to)? Will that hurt their longevity?

I've found a LDS-HTC512RI that's rated at 3.5 cd. I might try that one.

 

[audioguru]

The Lumex display is very bright at 3.5 cd or 3500 mcd. It might be seen when in the shade on a sunny day.

 

[Kris01]

Sounds like I might have found a winner!