Found this project interesting.
http://www.instructables.com/id/The-Int ... rapy-ligh/
Craig
Luxeon K2 white LED
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Yes, these hi-output Leds are useful - but a word of caution.
My reading of the article suggests that he's wired up the 4 Leds in parallel, then connected this (combo) to the 6v supply via a single (1.5ohm) resistor.
Not good practice, because each of the 4 Leds are almost certain to have slightly different forward voltages and (in this configuration) individual Led current limiting wouldn't be present.
Better to have a (current limiting) resistor for each Led.
(a brief read of the spec sheet also mentions 'current hogging' and the fact that forward voltage changes during the initial 'burn in' period)
Also, for a portable, battery operated arrangement, it's something of a short-sighted (imo) approach to base such a rig on std (non-rechargeable) batteries, which will become exhausted fairly quickly because of the high current drain of these partic Leds.
If I was doing this*, I'd double up the battery requirements to 8 AA NiMh cells (total nominal voltage 9.6) ... which would then allow these 4 Leds to be connected in 2 series -parallel chains (with own resistors) ... this would half the current drain / double the life ... all for the extra weight of 4 more AAs.
(but even if didn't go this route, at least base the rig on re-chargeable batts)
*:)
Well, over the last month, I've essentially built a much, much smaller, less powerful rig to clip on the end of my recently acquired MPE 65 ... so that I can shed a bit of light on the (dim) scene at higher mags
I'm using 4 std hi-output (12kmcd) Leds driven by a Nimh PP3 equivalent ... which is located in a hollowed out flash bracket handle.
pp
( a google search on 'connecting leds' will give further details of the above, but I can provide more info if nec.)
My reading of the article suggests that he's wired up the 4 Leds in parallel, then connected this (combo) to the 6v supply via a single (1.5ohm) resistor.
Not good practice, because each of the 4 Leds are almost certain to have slightly different forward voltages and (in this configuration) individual Led current limiting wouldn't be present.
Better to have a (current limiting) resistor for each Led.
(a brief read of the spec sheet also mentions 'current hogging' and the fact that forward voltage changes during the initial 'burn in' period)
Also, for a portable, battery operated arrangement, it's something of a short-sighted (imo) approach to base such a rig on std (non-rechargeable) batteries, which will become exhausted fairly quickly because of the high current drain of these partic Leds.
If I was doing this*, I'd double up the battery requirements to 8 AA NiMh cells (total nominal voltage 9.6) ... which would then allow these 4 Leds to be connected in 2 series -parallel chains (with own resistors) ... this would half the current drain / double the life ... all for the extra weight of 4 more AAs.
(but even if didn't go this route, at least base the rig on re-chargeable batts)
*:)
Well, over the last month, I've essentially built a much, much smaller, less powerful rig to clip on the end of my recently acquired MPE 65 ... so that I can shed a bit of light on the (dim) scene at higher mags
I'm using 4 std hi-output (12kmcd) Leds driven by a Nimh PP3 equivalent ... which is located in a hollowed out flash bracket handle.
pp
( a google search on 'connecting leds' will give further details of the above, but I can provide more info if nec.)