Subject: Re: Low-power LED questions
Date: Thu, 3 Oct 2002 08:10:57 -0400
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wrote in message
> This is a followup to my "Motorcycle HUD" thread. I found the Linx KH-
> series transmitter and receivers (thanks to the guy in comp.robotics.
> misc who suggested them!), and now I'm wondering about low-power LEDs.
> I'm trying to transmit the status of eight LEDs in a radar detector to
> eight LEDs mounted in my helmet. The Linx KH transmitter has eight
> input pins and a TE (transmit enable) which needs to be set to
> The eight LEDs in the radar detector need to be connected to the
> corresponding input lines on the transmitter. They also need to run
> into a big OR gate to drive the transmit enable (so the Tx only sends
> when the detector is going off).
> Without knowing what kind of LEDs are in the detector and what kind of
> voltages or currents drive them, what kind of 8-channel buffer and OR
> gate would you recommend? The Tx will be mounted on the bike, so the
> low-power isn't super important.
> The receiver outputs will also need to be buffered to drive the eight
> LEDs in my helmet. As fas as I can tell, the KH series receiver
> latches onto the last received outputs, so I will need to enable
> the LED driver (or buffer) from the DATA line on the Rx (indicating
> data has been received). This is so the diodes will only be on when
> the LEDs on the radar detector are on.
> Again, what 8-channel buffer would you recommend? It needs to draw
> very low current when not enabled, and should drive fairly low-current
> LEDs when enabled.
> What LEDs would you recommend? I need green, orange and red. I
> can't find a mix'n'match mounting piece in DigiKey, am I looking in
> the right place? The LEDs should be low current, small, directional,
> and bright. *grin*
> Lumex has some 'panel mount' LEDs that might be what I want. DigiKey
> part numbers 67-1205-ND and 67-1213-ND.
Those are arrays of leds with leads.
Due to the limit space in your helmet, I would use individual surface mount
in this case you can mix and match colors as you wish...
I would use the LTST-C150KRKT, LTST-C150KGKT, LTST-C150KYKT from Liteon
They are much brighter than the array that you found (54mcd or 80mcd
depending on which datasheet you look at, instead of 10mcd for the array),
that means you can use less current for the same intensity.
Kingbright has similar parts too. Those are 1206 size.
LEDs exist in smaller size too, but then, it's getting hard to solder them.
You might also consider extra-thin flexible PCBs. Slight problem, PCBs will
cost you about $250 just for a prototype run.
> Thanks for any help you can provide.
> William Sitch, B.Eng., M.A.Sc. will(at)sitch.org http://will.sitch.org/