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general efficiency of LED's

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Simon:
I'm wondering what is the typical efficiency of a white LED ?

I have an old 8mm film projector I just spent the best part of 20 quuid on for a bulb but am wondering if i can replace the bulb with a led(s) to make replacement a non issue and increase it's efficiency on power consumption (100 W lamp), the lamp is run off a 12V transformer so having the power available is not a problem

RayJones:
If I recall correctly, a Halogen bulb runs at something like 20-25 lumens / watt

So you have something like 2500 Lumens to create.

The typical best available LEDs at the moment are 80 or lumens/watt, so you'd need a fair stack of LEDs to get the same level of light, not considering heatsinking or even focusing all those individual light sources for projection.

Unfortunately the halogen bulb is still most likely the best choice for now.

Simon:
hm 25-30 W of led, can you get a single led to make that ?
my consideration was that the led would emit a faily focused beam so should be optically more efficient too ?

Zero999:
Yes you can buy 25W LEDs but it isn't that simple.

The colour rendering index of LEDs is inferior to halogen so you might mess the colour up.

Anyway are you sure it's halogen? Some of the better projectors use HID which is more efficient, although £20 seems too cheap for HID unless you got a cheap ebay deal.

You're looking at more than £20 for an LED in that power range but of course it will probably never need replacing to you might save in the long run.

Here's a link to such an LED on RS, £33.50 including VAT, then you need a heat sink and an SMPS.
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6491373

What voltage does the lamp in the projector run at? If it's something like 12V or 24V it might make it easier to buy/build an SMPS rather than mains.

Simon:
this is a 1960's 8 mm film projector and is one of the few that uses a 12v bulb so yes I have a perfect power source and available space for a SMPS, I can use the original bulb as a plug in so as to not damage the projector and ultimatel;y owing to the popularity of this projector might make a nice project that could become a saleable product

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