Jinx wrote:
> A few weeks ago someone mentioned seeing white LEDs powered
> by mains. I'd seen it too but couldn't remember where
>
> Found this in one of my pdf stashes when looking for something else
>
> http://home.clear.net.nz/pages/joecolquitt/acwhiteleds.pdf
>
> 11kB
>
>

RE the PDF design:

Why use back-to-back LEDs? One can simply use a full wave rectifier and then use only one direction of LEDs.

Second, since each LED has a significant voltage drop, the voltage drop of the string could be quite large.  This reduces the drop across the resistor.  A 1K resistor can't be optimal for a single LED *and* a string of 12?

I've built some "fireflies in a bottle" decorations.  These operate on 120V using a full wave rectifier, fuse and ~500ohm resistor.  The resulting rectified DC current feeds a series of 55 yellow LED's.  These have proved to be very durable.

...Alan

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