Driver for luxeon leds

[booth multiplier]

Dear All,
I'd like to built a driver circuitry for 8 Luxeon leds in series.
Each of them has a forward voltage at 3.5 V at 350 mA. 8 in series
makes 28V. I have applied the 28 volt works fine, but if I want to
make them flash it's not working, they simply don't flash. The ON
OFF sequence is like this: 1 sec OFF, 0.4sec ON, 0.1 sec OFF,0.4sec
ON, 0.1 sec OFF AND SO ON. Do I need a higher voltage for flashing?
Thanks

 

[Adam Aglionby]

"booth multiplier" <boothmultipler@hotmail.com> wrote in message
news:24160f43.0412010351.84cbc6d@posting.google.com...

Dear All,
I'd like to built a driver circuitry for 8 Luxeon leds in series.
Each of them has a forward voltage at 3.5 V at 350 mA. 8 in series
makes 28V. I have applied the 28 volt works fine, but if I want to
make them flash it's not working, they simply don't flash. The ON
OFF sequence is like this: 1 sec OFF, 0.4sec ON, 0.1 sec OFF,0.4sec
ON, 0.1 sec OFF AND SO ON. Do I need a higher voltage for flashing?
Thanks

Your thinking voltage when its better to think current. Vf of LEDs can be
fairly variable, wireing then is series is fine, but you want to think of
350mA roughly at whatever the Vf settles at.

1W LS will take up to 1A at low duty cycle, look up the data sheet at
Lumileds , there is an application sheet for using them as a flash for
mobile phone cameras.

400mS is possibly a bit long tto go as high as an amp for longetivity but
genuine Stars will take a suprising amount of abuse.

Look to use a constant current driver not voltage though.

Adam

 

boothmultipler@hotmail.com (booth multiplier) wrote:

I'd like to built a driver circuitry for 8 Luxeon leds in series.

I built a current regulator based on an LM2941 that drives one Luxeon
with about 270MA from 4.2 to over 18V (as high as my bench supply
goes). It's got an on/off pin that you can use for logic-level
control.

[I'm building a solar powered beacon, with a PIC for control,, but
don't hold your breath. 8*]

 

[trustandhonor2]

William P.N. Smith wrote in message news:<j942r01ul7e0cvejd3v32q93ombj9ou1m9@4ax.com>...

boothmultipler@hotmail.com (booth multiplier) wrote:
I'd like to built a driver circuitry for 8 Luxeon leds in series.

I built a current regulator based on an LM2941 that drives one Luxeon
with about 270MA from 4.2 to over 18V (as high as my bench supply
goes). It's got an on/off pin that you can use for logic-level
control.

[I'm building a solar powered beacon, with a PIC for control,, but
don't hold your breath. 8*]

ask Linear Technology for Application Notes and Driver circuits for
Luxeon LEDs, Maybe LT1618 and LTC3441 do the job for portable Battery
systems with torch and Flash functionality. www.linear.com