[sdiy] Re:

[harry]

The Voltage Follower is running in linear mode... the transistor is not
saturated. In the PWM example the transistor is saturated, so the power
dissipation is very low.

LEDs running at low currents will operate in an area where brightness
differences
are very obvious. By pulsing them at a higher current, the eye is fooled into
thinking
that the LEDs are brighter, and the physical limits of the LED are overcome at
the
same time. The eye sees the flashing LED as brighter than the average... it is
more of a peak detector in that regard.

If you want to "light up" a synth we are looking at several hundred millamps
to
possibly a couple of amps. Every advantage helps.

H^) harry

matti wrote:

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

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