Flashing 1W LED

[joeling]

Hi,

Merry Christmas & a Happy New Year !

Not sure if the topic has been covered but I would like to have a simple circuit that can drive a 1W LED (like the 1W luxeon ones) wih flashing. The input voltage can either be 3S or 5V or 6V. I don't care about the precise control of the flashing just as long as it flashes.

Can anyone enlighten me ? Most of the circuits I found are only suitable for low powered leds.

My intention for this is to affix 1 LED at the front of my 4 rotor craft so that I can id where the front is.

Thank you.

Regards,
Joe Ling

[Malc C]

Just use one of the low powered circuits to drive a transitor arrangement, or opto relay (or normal relay for that matter) so its switches the supply to the LED

[norbique]

joeling,

There are many different circuits to drive high power LEDs. Look around and ask your question here: http://www.candlepowerforums.com/vb/ they may be able to help you.

[SkynetAir]

Hi Joe.

You could use a 555 timer where you could control the mark-space ratio of the pulse of light, and connect the output of the 555 to a power NPN darlington transistor like a TIP121, which I think has a gain of about 10,000. That should control a 1W led ok.

Andy

[norbique]

Yes! The 555 can be used to generate the square wave, but you all forget to mention one very important thing.

LEDs are driven by current, not voltage! You need to limit the current going through them.
You need a Current regulated DC/DC converter to drive high power LEDs.
Try looking up National Semiconductors they have a huge variety of DC/DC converters, some designed especially for driving LEDs.

The 1W Luxeon LEDs are driven at 350mA nominal current. With that current flowing through them the LED voltage is roughly 3.4Volts.
Look at the datasheet: http://www.lumileds.com/pdfs/DS25.pdf (page 6)

In my opinion, controlling the LED current is the way to go, but if you still choose to use the 555 with a transistor to switch the LED on/off, make sure you don't exceed 4V going to the LED.
Look at the voltage/current graphs in the datasheet. (page 10) A slight rise in voltage results quite a current increase. You can easily kill the LED.
Also don't forget to cool the LED. Power LEDs can produce quite an amount of heat!

[SkynetAir]

Yeah, that is right. If the LED drops 4.2v, then given a 5v supply a 2R2 resistor will reduce the current to 350mA.

[ghoti]

...

[mem]

This low cost 1amp strobe driving board may be what you are looking for: http://www.dealextreme.com/details.dx/sku.7612