Bulbs....

Can someone please explain the difference between the halogen bulbs used in home lighting that has about 5000 hours bulb life, and the xenon-halogen bulbs used in tactical flashlights that last about 20 hours?

That would really clear things up, thanks!

YC

I will take a GUESS at this. The home bulbs are not being driven as hard as bulbs in a hand-held light. I'm probably wrong on that though.

check out this site - it's probably more than you want to know - but very thorough:

http://www.misty.com/people/don/bulb1.html

hmm.. I still don't get it

I remembered that somewhere mentioned that the E2 is approximately 5 watts. How would that compare to say a 5 or 10 watt halogen bike light?

YC

yclo,

bulbs (all others factors aside) do have a so-called efficiency - means the number of lumens (light) they put out for one watt of power put in - this can range from single digit to possiby 25 for the best halogens - HID seem to be even much better. To compare the E2 against bike halogen lights you need to know how much lumens they put out - not just the wattage - in your expample my guestimate is that E2/5W should equal a 5W bike halogen light - if the halogen bulb is a good one.

On the issue of lifetime - (and I´m not a specialist here - so this is just my 2 cents - others better than me on that should/might add/correct) you do have a relation between lifetime and efficiency - typically the more efficient bulbs do have a shorter life time - when you "underdrive" a bulb (lower filament temperature) it lives longer at the cost of lower efficiency (lumens per watt) - when you "overdrive" a bulb (higher filamant temperature) it gets more efficient but lives shorter.

As the requirements at home are different than in a flashlight (who would buy a bulb again when one was failing after 20 hours of being lit at home - possibly the second night already ?) the bulb design varies.

One other point is that it seems easier to design efficient AND long life bulbs at higher wattages like the 20/35/50 Watt osram MR16 bulbs at aprox 25lm/Watt and 4000 hours.

On the flashlight bulbs ýou habe "high output bulbs" at like 4V / 0,85A giving you 60 lumens for 25 hours - while a typical "miner" bulb would give you just 48 lumens at 4V / 1A but for a much longer 600 hours. Again here the bulb is designed for the purpose - the mining company just doesn´t want to buy a new bulb every couple of days while the average flashlight user is more concerned about battery usage vs light output.

On Willie Hunts pages is a nice chart on that - for a given 4V bulb going up from 4V to 4,4V (10%) relative light output goes up by 40% (efficiency by 23%) but life hours go down to 2 from 25. Going down 10% to 3.6V the relative light output is 75% (efficieny 90%) but life hours are going to approx. 1000

Hope this helps

Klaus

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by yclo:
Can someone please explain the difference between the halogen bulbs used in home lighting that has about 5000 hours bulb life, and the xenon-halogen bulbs used in tactical flashlights that last about 20 hours?<HR></BLOCKQUOTE>

Klaus already said the most important things.

I want to add that actually if you get the wattage and the efficiency of a bulb, it does not say too much without the lifetime. You have to compare bulbs of a similar wattage and at the same lifetime to tell which one is the better quality.
Lifetime is the numbers of hours (usually) which 50% of the bulbs will life. That means half of the bulbs will fail earlier, the othe half later.

It was a good example for how you can forge technical numbers:
People wrote several years ago, that LEDs were more efficient tahn incandescents (which was not true at this time). But when you compare light sources of the same lifetime, you have to run an incandescent bulb pretty low to get 100,000 hours life. And under this circumstances LEDs where superior even several years ago.