Choosing correct LED mcd for outdoor indication

[peterlonz]

I don't wish to ask dumb questions about basic LED applications but ...
Yesterday I bought a 12 mcd, 5mm Dia, red LED, through hole mount.
It was to replace an unexpected failure of the previous unit: supposed to suit 12VDC supply & containing a built in resistor.
The application is a 12VDC regulated, 2 amp capable, PSU.
The original LED was nice & bright & easily seen outdoors.
This was good because the 240VAC power on/off rocker switch containing a red neon is not sufficiently bright
My replacement LED is relatively dim & I need to cup my hand over it (when outdoors) to be sure its on.
Now by chance I made a silly mistake & used a 100 ohm resistor instead of the 300 Ohm which is what I calculated should be used.
So I am expecting the LED to fail soon, but it should be much brighter surely with the higher current.
I can't figure out this dilemna.
I suspect 12 mcd (@ $0.25 ) is probably a poor choice but there seems very little choice between this low output & the much higher rated 5000 mcd & above.
Suggestions please?

 

[vk6kro]

Yes, that is a very low powered LED. 1 Candela is roughly the brightness of one candle.

So 12 mcd is about 1% of 1 Candela. Not much.
5000 mcd is 5 candles, so, much better.

You can get a brighter LED and just run less current through it. They are usually highly efficient, so try calculating the resistor with 20 mA flowing in it. Maybe 470 ohms.

 

[Perfection]

I'm thinking you're shopping at the wrong place. You can get pretty much any LED you can imagine! I like shopping at Digikey (http://www.digikey.com) for parts.

5000mcd isn't really that much. Remember, a candle is 1000mcd.

Here's what I'd go with: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=C4SMF-RJS-CT0W0BB2CT-ND

Rating is 2640mcd price $0.20

From the Datasheet.

This oval LED is specifically designed for variable-message signs and passengerinformation
signs. The oval-shaped radiation pattern and high luminous intensity
ensure that these devices are excellent for wide-field-of-view outdoor applications
where a wide viewing angle and readability in sunlight are essential.
These lamps are made with an advanced optical-grade epoxy that offers superior
high-temperature and high-moisture-resistance performance in outdoor signal
and sign applications. The encapsulation resin contains anti-UV material in order
to reduce the effects of long-term exposure to direct sunlight.