Help - LED Conversion?

Can someone help me with a couple simple conversion questions. I'm pretty good with electronics, but new to LED lighting. I read over most of these postings but could not find the answers to my questions.

I'm trying to convert a (3) cell flashlight over to use LEDs so the batteries last longer. I want the light brightness to be very similar to the existing PR3 bulb, which is rated at 3.57 volts and 500mA.

I'm trying to add about 50% battery life , but don't want to suffer on light.

I can handle the assembly of the circuit. I don't know which LED's to use or where to get them.

Questions:
Which LED should I use? (I want white light)
How many should I use to equal a PR3 bulb?
Where can I purchase them? (Radio Shack?)
Is one LED solution lower cost than the other?

Thanks

PS: This is a great message board. I just found it tonight. I thought I was the only flashlight nut around. I't good to know I'm no alone.

Hi Dave, it can be a little slow around here on the weekends as wives drag us away from our beloved board. However, if your going to be up for a while I would look for one of Brock`s post and link to his site. Lot`s of great links there as well as reviews. Be sure to click on Craig Johnson`s link for more detailed info...both great stuff. You will find some companies making ready made 3 LED P-R replacements and might be worth your while buying one to gain some idea of what to expect from LED`s. But either way there`s plenty to keep you up all night

I would suggest getting a premade LED in a PR base. You can do it yourself, but if you get a premade one usually they are made with the brightest LED's.

Brock

Welcome Dave!

Which LED should I use? (I want white light)
Far as I know, the best white solution is Nichia's NSPW500BS. 10 of these in parallel should draw about 250ma. There's some new LED thing coming out that should be brighter. We'll see...

How many should I use to equal a PR3 bulb?
I doubt if 10 of them will be as bright as the original krypton bulb.
Anybody know the efficiency of krypton vs. leds? %?

Where can I purchase them? (Radio Shack?)
NOT Radio Shack. Best bet I've found so far is Paul @ www.white-leds.net ($1.75 for the Nichias I mentioned).

Is one LED solution lower cost than the other?
Well, that's the current subject of great debate in another topic ( 44 Led Maglite )

Welcome to my nightmare!