Electronics, Lighting, & Gadgets - Completely newbie DIY light questions

OK, I want to take a stab at building a bike light but have basically no knowledge of electronics. So I have a few questions:

1) I'm looking at this emitter (http://www.dealextreme.com/details.dx/sku.16145) - I believe this is a Cree High Power XLamp similar to those used in the highly regarded Ayup lightsets (http://www.ayup.com.au/specs.php#CREE%20LIGHTSETS). If I don't want to have various modes (strobe, 1/2 power etc) is it simple a matter of wiring to a suitable battery (no driver required)? I'm looking at something like these for powering it (http://www.dealextreme.com/details.dx/sku.5790).

2) The voltage rating of the emitter is 3.2-3.5v but all the batteries are 3.6-3.7v. Does this necessitate a resistor to just drag the voltage down a tad or is there sufficient latitude in the ratings that it's not really going to matter?

3) Is there a way to calculate whether a heat sink will be required or is it just safer to use one regardless?

4) Does anyone have any tips regarding reflectors or lenses?

I know I can buy lights (in fact I already have one) but I'm an obsessed tinkerer and just want to do it as a bit of a project with the kids.

cheers

'k

1) The LED can be direct driven, but you might be better off with a P7 as it could put out more lumens.

2) Use a P7 instead they run at 3.6 - 3.7 volts.

3) You WILL need a heatsink.

4) What are you going to use the finished light for ?

1) The LED can be direct driven, but you might be better off with a P7 as it could put out more lumens.
2) Use a P7 instead they run at 3.6 - 3.7 volts.

4) What are you going to use the finished light for ?

Thanks for the response,

Is this (http://www.dealextreme.com/details.dx/sku.12721) the P7 you're referring to? Would the included heatsink be sufficient?

Will be used on a roadie and maybe for running if it can be made compact enough. Not averse to using two on the bike if required - one wide beam one 'pencil' beam.

Is this (http://www.dealextreme.com/details.dx/sku.12721) the P7 you're referring to? Would the included heatsink be sufficient?

Will be used on a roadie and maybe for running if it can be made compact enough. Not averse to using two on the bike if required - one wide beam one 'pencil' beam.

Yes, that's a P7 on a star.

Where it says heatsink base what it actually means is the LED is on a star that can be fixed to a heatsink with thermal epoxy or thermal tape, so, no the included heatsink would not be sufficient unless you ran it on very low power.

I don't fancy your chances of getting a pencil beam out of a P7 without some elaborate lenses and you might not be able to with a M-CE either.

FYI most of the P7 (probably MC-E too) torches run the LED at a lower level than max, which has the benefits of manageable heat output and better runtime.

You'll need a lot of heatsinking for either of those chips at full power.

Hope this helps.

:thumb:

It's a lot better to find a constant current driver for your LEDs instead of wiring them straight to your batteries. It will save you a lot of headaches. The good ones also do nice things like protect your batteries and LEDs from things like overheating and overdischarging.