Always aiming for the pure minimalist design, here is QLF6, an amazingly
simple but effective 4 channel LED controller which requires just 14 parts
plus LEDs.

This circuit works nicely from 9V to about 2.4V with just minor changes in
brightness and frequencies.

It takes advantage of the build-in LM339 output current limiting.

The current per output is about 20ma so several matched high efficiency LEDs
can be driven in parallel. At higher supply voltage (9V max) use series LEDs
for higher efficiency and reduced LM339 heating.

PWM makes QLF6 efficient in part due to high peak optical pulses which are
perceived brighter than the light of LEDs operating at equivalent dc
current.

The oscillator frequency is stabilized with a simple voltage regulator
across the 74HC14 chip power pins using the forward voltage drop of LED5.
This also allows the circuit to operate directly from 9V.

The slow oscillators that control LED 1-4 use non-critical resistor values
between 1M and 10M. The maximum values shown give a maximum fade time for
LED 1 of a few seconds.

The 100K pot can be adjusted from all LEDs OFF, to random flashing, to
random fading, to some weird stuff near the end of rotation. A rainbow LED
connected to LED 1-3 can be used to The QLF6 circuit generates the full
spectrum of colors and hues, which is visually a much more appealing effect
than the recent Spectrummer design which only generated pastel hues.

QLF6 is a true random fader/flasher as the PWM switching transients seems to
break up any attempt of the oscillators to phase lock even if the slow
oscillators are close in frequency.

This circuit can also be used to drive small motors to generate some bizarre
random motion, say no more!

enjoy

wilf




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