New Bike Light - 19 x White LEDs

On Fri, 04 Feb 2005 at 12:00 GMT, Gags (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

Just finished posting my latest homemade bike light on my site.

http://www.users.tpg.com.au/adsl4xun/lights-v9.htm

It comprises 19 x 10,000 mcd white LEDs and I am pretty happy with it.

White LEDs? I bought the jaycar 19 red LEDs, but haven't assembled it
yet.

I wasn;t aware of a white LED version. How bright in SI standard
halogen units? 😉

--
TimC -- http://astronomy.swin.edu.au/staff/tconnors/
21/06/01: * It's a solar eclipse.
* Mars is really close to the Earth.
* It's the winter solstice.
and * 42'nd death day of late Douglas Adams

TimC said:

I wasn;t aware of a white LED version. How bright in SI standard
halogen units? 😉

That depends on the viewing angle, ie how focussed. They are
generally of similar efficiency to halogens, and much lower than
florescent. But you can efficiently dim an LED, or make it flash.

http://www.oatleyelectronics.com/leds.htm

EL8W13 13 LUMEN 8mm WHITE LED: Luminous Flux: 13 lumens, Size: 8mm,
Lens Type: Water Clear, Viewing Angle: 55°, Forward Voltage: 3.5V
typical @ IF = 150mA. $2.70

So that one actually quotes lumens!
A few of them, plus maybe some spot LEDs of a lens would make a good
bike light.

On Sat, 05 Feb 2005 at 02:08 GMT, Mike (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

TimC said:

I wasn;t aware of a white LED version. How bright in SI standard
halogen units? 😉

....

Quoted message said:

EL8W13 13 LUMEN 8mm WHITE LED: Luminous Flux: 13 lumens, Size: 8mm,
Lens Type: Water Clear, Viewing Angle: 55°, Forward Voltage: 3.5V
typical @ IF = 150mA. $2.70

So that one actually quotes lumens!
A few of them, plus maybe some spot LEDs of a lens would make a good
bike light.

Sorry - I was referring specifically to the 19 LED bayonet fitting
"bulbs".

You say "similar" - I know Luxeons are more efficient than halogen,
and I thought regular superbright LEDs were more efficient than
halogen too. You're saying they're not?

I went home via gardiners ck last night. Because there are no street
lights, I did a test of my 3 LED head strap light from Jaycar - and I
can't see anything at almost any speed. It's definitely a "be seen
rather than to see" light, and I don't know how good it is even as a
"be seen" light. Good thing it is only my emergency light for when I
forget to change the batteries in the main light.

--
TimC -- http://astronomy.swin.edu.au/staff/tconnors/
Smash head on keyboard to continue.

"Gags" <gags_44nospamatnospamtpg.com.au> wrote in message
news:[email hidden]...

Quoted message said:

Just finished posting my latest homemade bike light on my site.

http://www.users.tpg.com.au/adsl4xun/lights-v9.htm

It comprises 19 x 10,000 mcd white LEDs and I am pretty happy with it.

Now I just have to decide if the next light will be a Luxeon or a HID????

Ride On,

Gags

firstly. nice
now for the stupid questions
what wattage are the R's? i think 1/4 watt would do for most of them?
pretty much any diode would do wouldnt it?
and what needs to be change to make this run off 12-13V?
thanks
stu

[censored] smith part numbers would be great 😉

stu said:

what wattage are the R's? i think 1/4 watt would do for most of them?
pretty much any diode would do wouldnt it?
and what needs to be change to make this run off 12-13V?

P=I^2*R, so given 30mA per LED, then the 22R resistors onlt dissipate 20mW each.

The 1R resistor dissipates 320mW, so a 1/2 watt or 1 watt one would be good there.

1N914 or 1N4148s would be good as the diodes.

To run this off 12V with reasonable efficiency, you'd want to put the LEDs into strings of 2 or 3.

With strings of two, 7.5 odd volts would be across the LEDs, with 4.5 across the resistors and transistor, so it would only be about 60% efficient.

With strings of 3, you'd have 11.3 odd volts across the LEDs, leaving very little headroom for variations in battery voltage, but it would be a lot more efficient.

Regards,

Suzy

suzyj said:

stu said:

what wattage are the R's? i think 1/4 watt would do for most of

them?

Quoted message said:

pretty much any diode would do wouldnt it?
and what needs to be change to make this run off 12-13V?

P=I^2*R, so given 30mA per LED, then the 22R resistors onlt dissipate
20mW each.

The 1R resistor dissipates 320mW, so a 1/2 watt or 1 watt one would be
good there.

1N914 or 1N4148s would be good as the diodes.

To run this off 12V with reasonable efficiency, you'd want to put the
LEDs into strings of 2 or 3.

With strings of two, 7.5 odd volts would be across the LEDs, with 4.5
across the resistors and transistor, so it would only be about 60%
efficient.

With strings of 3, you'd have 11.3 odd volts across the LEDs, leaving
very little headroom for variations in battery voltage, but it would be
a lot more efficient.

Regards,

Suzy

If you're running off Nicads or NiMh the minimum recommended cell
voltage is about 1 volt per cell, so with 10 cells you want your light
to work down to 10 volts for maximum usage of your batteries.

Oscar