LED flashlight building basics

[wagsbags]

Not sure if this is the right place for this but is there a tutorial somewhere on the basics of building an LED flashlight? I'm an engineer so I'm comfortable with concepts like current, voltage etc. but I'd like to see an overview of what parts go into making the flashlight.

For instance, is a driver used in place of a resistor or in addition to? How is heatsinking normally done?

The motivation for this is my friend and I plan on building a bike light ~500 lumens or so. We're thinking 2 or 3 MC-E leds but aren't quite sure on how to go about it.

P.S. what's the deal with 2s2p vs. 4s?

 

[old4570]

Head over to DX = DealExtreme.com ...

Lots of pictures of flashlights pulled apart . Check out the DIY parts , check the modified section of this forum ...

Ask questions ...

Yes basics of flashlight = Cree + Driver ...

Driver will be - Input voltage - output 3.7v but Amps may vary .

Input voltage will depend on batteries ... AA - CR123A etc

Then there is MC-E and P7 ,, Cree [ What ever ]

Yes you can use a resistor to drop voltage ... [ Direct Drive ]

Ive just done a Cree P4 mod on my old Romisen + 5 Mode Driver .

Dep on the batt used , its giving the P4 o.7 to o.8mA on Hi ..
The Cree P4 being rated @ 80 to 86Lumen at 350mA ...
On Direct drive my two other mods are only doing o.5mA

 

[BillyNoMates]

We're thinking 2 or 3 MC-E leds but aren't quite sure on how to go about it.

P.S. what's the deal with 2s2p vs. 4s?

The MC-E led has four separate die in one package. Each of the little led chips can be connected independently. This allows the user to choose how to connect up the chips. You could choose to wires all die in series (4s), all die in parallel (4s) or a series combination of two die in parallel (2s2p) or any other combination you can think of. By contrast the SSC-P7 comes pre-configured in 4p guise.

The advantages of choose the connection options give you the flexibility to choose the drive that best fits your application (usually battery). A 4s configuration will need a voltage of ~13.6V and a current of 700mA for max rated output. 4p will need ~3.4V at 2.8A. 2s2p will be half way in between (~6.8V at 1.4A).

A driver is really a power controller that allows the current to be kept constant as the Vf of the LEDs and the battery voltage vary. Some drivers may also offer different modes such as strobe or different brightness settings.

BTW, a lamp based on 3x MC-E will be a lot more tha 500lm (each LED can be driven at almost 10W) !!