What's the most efficient LED _color_?

[William P.N. Smith]

William P.N. Smith <wpns@compusmiths.com> wrote:

Watson A.Name - 'Watt Sun' <alondra101@hotmail.com> wrote:
Luxeon Stars take several hundred mA, are you aware of that?

I think I'll be able to crank my pulse current up to at least 50
milliamps, which is the low end of the spec for the red-orange
Star/Emitter.

I built a prototype this afternoon with the red-orange Luxeon, using
the 74AC14 circuit from
(http://www.imagineeringezine.com/PDF-FILES/ac14fls.pdf ), and after
stacking four chips on top of each other (8 source drivers, 12 sink
drivers) and cranking the voltage to about 2.6 volts, I got the
average current during the pulse up to about 200 mA.

It's bright, but I think I'm going to re-engineer it using a better
(large transistor or FET) driver (maybe like
http://www.imagineeringezine.com/PDF-FILES/1vled3.pdf or maybe just a
555) to give a peak pulse current in the half-amp range, and maybe run
it off a 4V lead-acid battery. I'm probably going to pick up a couple
of other colors (Green and Cyan) and make a portable test beacon to
see which color is brighter at night for a given current.

--
William Smith wpns@compusmiths.com N1JBJ@amsat.org
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[William P.N. Smith]

Lizard Blizzard <NOSPAM@rsccd.org> wrote:

You really don't need a largish lead acid battery. Three or four AA
Ni-MH rechargables will do just fine, considering that peak flashiung
current is high but the average current is very low. Four Ni-MH cells
will last for weeks with a very bright blue or white flasher. Just use
some good bypass caps across the batt.

I'd like really long runtimes, like on the order of a year. According
to my calculations I can do this with Enersys (nee Hawker (nee Gates))
Cyclon batteries of the BC (25AH) size, though I'm also looking at
smaller batteries with tiny solar panels...

have to worry about power dissipation, just low Vce(sat) and good beta
holdup at high currents. If I were driving a Luxeon Star, I'd try to
get a peak current of several amps. The low duty cycle means little
power will be dissipated.

They list peak currents of 500 or 550 mA in pulsed mode, though they
don't say anything else about pulse widths...

--
William Smith wpns@compusmiths.com N1JBJ@amsat.org
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[Watson A.Name - 'Watt Sun]

In article <1s6ljvglo5qv699ktnvhst4vhfhna7mot0@4ax.com>,
wpns@compusmiths.com mentioned...

Lizard Blizzard <NOSPAM@rsccd.org> wrote:
You really don't need a largish lead acid battery. Three or four AA
Ni-MH rechargables will do just fine, considering that peak flashiung
current is high but the average current is very low. Four Ni-MH cells
will last for weeks with a very bright blue or white flasher. Just use
some good bypass caps across the batt.

I'd like really long runtimes, like on the order of a year. According
to my calculations I can do this with Enersys (nee Hawker (nee Gates))
Cyclon batteries of the BC (25AH) size, though I'm also looking at
smaller batteries with tiny solar panels...

I think that the battery will lose asubstantial amount of its charge
ove time, even without having a low current load. So you will have to
recharge it every few months.

have to worry about power dissipation, just low Vce(sat) and good beta
holdup at high currents. If I were driving a Luxeon Star, I'd try to
get a peak current of several amps. The low duty cycle means little
power will be dissipated.

They list peak currents of 500 or 550 mA in pulsed mode, though they
don't say anything else about pulse widths...

That current level seems about what is used for pulses in regular 5 mm
LEDs.

--
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[Don Klipstein]

In article <MPG.19a4c141bc1152f989bb9@news.inreach.net>, Watson A.Name -
'Watt Sun' wrote:

In article <1s6ljvglo5qv699ktnvhst4vhfhna7mot0@4ax.com>,
wpns@compusmiths.com mentioned...
Lizard Blizzard <NOSPAM@rsccd.org> wrote:
(apparantly regarding Lumileds Luxeon high power LEDs that typically

require heatsinking)

They list peak currents of 500 or 550 mA in pulsed mode, though they
don't say anything else about pulse widths...

That current level seems about what is used for pulses in regular 5 mm
LEDs.

Somewhat true for infrared types. Such high peak currents for visible
LEDs of "regular size" 5 mm or T1-3/4 or T-1.75 or smaller are not usual
but are more in the way of abuse.

- Don Klipstein (don@misty.com, http://www.misty.com/~don/ledx.html)

 

[Don Klipstein]

In <nr5vjvs8rkj1nseqrjanu7ocqamge3bm0d@4ax.com>, William P.N. Smith wrote:

don@manx.misty.com (Don Klipstein) wrote:
'Watt Sun' wrote:
wpns@compusmiths.com mentioned...
Lizard Blizzard <NOSPAM@rsccd.org> wrote:
(apparantly regarding Lumileds Luxeon high power LEDs that typically
require heatsinking)
They list peak currents of 500 or 550 mA in pulsed mode, though they
don't say anything else about pulse widths...

That current level seems about what is used for pulses in regular 5 mm
LEDs.

Somewhat true for infrared types. Such high peak currents for visible
LEDs of "regular size" 5 mm or T1-3/4 or T-1.75 or smaller are not usual
but are more in the way of abuse.

OK, what pulse width do you think would be allowable for a Luxeon
that's rated at 350mA with a peak pulse current of 500 mA? Seconds,
milliseconds, microseconds?

According to the datasheet, 500 mA max for a milisecond or less if I
remember correctly. I just looked at their "DS23" datasheet and saw 500
or 550 mA depending on color but did not see a time limit. I have
had one survive a little more than that for several seconds (still works
now), but there is no guarantee.

- Don Klipstein (don@misty.com)