Here is the polished up tested design, Quad LED Fader 5, which works on the
same principle as QLF4 but uses a LM339 quad comparator instead of the LM324
quad opamp. The advantage is the LM339 has an open collector output which
permits rail to rail output signal swing.

I have improved the QLF5 output drivers which are now configured as 60mA
current sources to maintain even LED brightness over a voltage range of 3.2V
to 2.4V when the battery supply drops. The output current is limited when
the 2N3906 starts to turn on as the current through the 10 resistor is about
50ma and the 2N3906 shunts base current away from the PN2907.

The 74HC14 oscillators now also have stable output frequencies by regulating
the chip Vcc line with a red LED used as a 2V "zener".

The improved QLF5 circuit is only slightly more complex using a total of 33
components in addition to the 40 LEDs. However the perfomance is greatly
improve over the simpler QFL4 design.

The QLF5 can also be used with 9V battery for random rainbow cycling of
tricolor LEDs. With 3 LEDs, one set of 6 components can be removed to reduce
parts count.

When the supply voltage is increased to 9V or 12V, 3 or 4 LEDs (or 3 or 4
groups of 3 LEDs) can be driven in series for better matching of brighness.

With a 9-12V battery supply, the PN2907 1K base resistors must be increased
to 10K and the 10 ohm current sensing resistors should be made 33 ohm for
20mA current. The 1K ohm resistor in series with the 74HC14 Vcc line should
be raised to 10K.

enjoy

wilf


----- Original Message -----
From: "Wilf Rigter" <wrigter@...>
To: <beam@yahoogroups.com>
Sent: Sunday, May 25, 2003 7:05 AM
Subject: Re: [beam] Re: Slow pulsar


> However the brighness of the LEDs is directly proportional to Vcc and
> some kind of compensation would be very useful. I'm working on it.





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