[sdiy] Re:

[Trevor Page]

Hi,

> How is this better and more efficient than a voltage follower and a
> current-limiting resistor?

This way you'd get linear control over LED light intensity with varying
control voltage. Remember, as with any diode, a LED doesn't exhibit a linear
voltage vs. current relationship. In other words, linearly varying the LED
supply voltage (eg with a voltage follower)  won't produce a very linear
change in light intensity.

Trev


> enjoy
>
>
> On Sun, 3 Feb 2002, harry wrote:
>
> > Ahhh... you want a voltage to pulse width converter. Its easy. You need
> > a
> > triangle or sawtooth wave (only one per synth) at a fixed (you choose
> > it) frequency... and a comparator for each LED channel. You make it work
> > so that increasing voltage equals a longer pulse... then drive all the
> > LED from a transistor on the
> > comparator output.
> >
> > Caveat: This is a "switching" power supply. Unless you are careful, all
> > these modulated LEDs are going to wreak havoc with your power supply and
> > or
> > radiate into the audio. It is the best and most efficient way to
> > modulate an
> > LED intensity.
> >
> > H^) harry
>
> *snip*
>
> -
> you stupid vulgar greedy american death-sucker
> some trillions of years ago a sloppy dirty giant flicked grease
> from his fingers
> one of those gobs of grease is our universe on the way to the floor
> *splat*
>
>