[Laser] off topic

[James Whitfield]

Bob

You did not say if you were trying to mount an LED ( presumably a 1 Watt or
3 Watt version ) in a standard bicycle headlamp fixture, or if you are
"starting sorta' from scratch".

If you are trying to put an LED into an existing fixture that will take a
standard size flashlight bulb, then you might look into the "replacement"
versions that are sold in hardware stores.  That may just drop in.

If you can tolerate a rather mechanically awkward solution, mount a
three-"C" or three-"D" cell flashlight, such as the Mag-Lite, which has an
adjustable focus by twisting the head.  The reflector in the head is a
paraboloid which will focus parallel rays to a point, or conversly direct
rays from a point source into parallel rays ( seen as a "spot" ).  The
filiment of a flashlight bulb is usually smaller than an LED emitter, thus
closer to a point source, and therefore procduces a tighter spot of light.
By moving the source forward or aft of the focus, the minimum spot size gets
bigger.

This may be closer to what you have in mind for a bicycle headlamp:  I have
tried to mount an LED from a string of Christmas Tree lights in the focus of
a 6V lantern flashlight.  The LEDs that I am using have a inverted conical
tip to make a more spherical pattern than other LEDs.  What you might try is
mounting the high power LED just aft of the focus.  You probably will have
to cut off the back of the reflector because the hole for a flashlight bulb
isn't big enough.  The reflector was designed for flashlight bulbs with the
filament ( point source ) forward and having some light emitted at a
rearward angle.  That "rearward" part of the reflector can be cut off if
necessary to accomodate the larger LED assembly, which will emit only
forward.

Let us know how your project works out.  It seems like it might be
applicable to "searchlight" beam for light communication.  Maybe not so far
off topic as you think.

James
 n5gui
----- Original Message -----
From: <riese-k3djc at juno.com>
To: <Laser at mailman.qth.net>
Sent: Monday, June 02, 2008 11:27 AM
Subject: [Laser] off topic


> any thoughts on how to use the higher powered leds as a bike headlamp
> would like to be able to broaden the ilumination to make it less of a
> spot light
>
> bob k3djc
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