Hello,

I am wanting to use the digital outputs on the mbed to drive LED's, now I think the digout is 3.3v... I need 3x LEDs (red, blue, & green)and need them as bright as possible. (the old style LED's, not surface mount)

Any recommendations on bright LED's I can use with the mbed? Ive had a quick look around farnells website but its hard to get a good idea how bright they will be.

Thanks ppl!

Steve

The brightness is in MCD

Milli Candella or lumins.

Try searching for hyper bright.

I would use Farnell's search, Pick size, color then sort by brightness.

But you need to check the current required by the LED vs the amount of current you can source from an mbed pin. Another option is to use some kind of LED driver.

Matt

The formulae is simple:

V drop for LED = 3.3 - LED Voltage.

R = V Drop LED / Desired current.

Typical 2 to 6 mA,

And 220 to 1 K ohm.

Hope this is helps

Ceri.

For smd I know that led like

1142615 (Farnell)

can bright a lot. Maybe they sell them in other package.

Regards Giuseppe

Brilliant thanks for the information.

I was looking at something like this...

http://uk.farnell.com/kingbright/l-7104qbc-g/led-3mm-blue-ultra-bright/dp/2080003?in_merch=New%20Products

Would that work if I put the correct resistor inline with it?

Anyone have any recommendations?

Vf for that led is 3v3 @ 20mA You can drive it only if you run it between 2mA and 15mA which cause less light but it works.

You are very close to the max output current of MBED. (pin)

If you only drive one LED then that will probably be ok.

I can't remember if max output current is 20 mA per pin, upto 100 mA total.

I think there is some good info if you keep clicking on The MBED pictures on home page.

Ceri