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'[EE]: Modern Relaxaition Oscillator'
2004\12\06@191316 by Ed Edmondson

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face
My wife is making a ceramic light house for a Christmas gift for her mother.
You know, the mother-in-law thing. I was wondering about installing a red
and white LED pair in the tower to simulate the tower beam. I was thinking
of slowly fading the front white LED and rear red LED and then reversing to
the second pair of LED's with the white in the rear red in the front. Then
the cycle repeats itself again.

Any suggestions on this and how to simply implement the circuitry?

Thanks,
Ed

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2004\12\06@195733 by Marcel Duchamp

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Two solutions come to mind: opamps and pics.

I recently wrote a little program for the 10F206 to generate 3 pwm
outputs to 3 leds.  They slowly pulsate at different rates and will go
into some garden path lanterns.  A fourth input pin will use a CdS
photocell to turn it on/off at night/day.

As for opamps, consider a state-variable oscillator.  These have two
integrators in series followed by an inverter that goes back around to
the input.  The 2 integrators give 'normal' and 'quadrature' (ie zero
and 90 degrees) phased sine waves.  Running each of these through linear
inverters produces four outputs: 0, 90, 180, and 270 degrees which
sounds a lot like what you might be looking for.  Details abound on the
net; for a dead-tree reference, check out Horowitz & Hill.

Good luck!
MD

Ed Edmondson wrote:
{Quote hidden}

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2004\12\06@200035 by Harold Hallikainen

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An 8 pin PIC with PWM output would do great! Using more parts, you could
do it with a dual op amp. Set one up to be an inverting integrator. Set
the other up to be an inverting schmitt trigger. The integrator will ramp
up and down between the two trip points.

Harold
(the ideal design has zero parts)

{Quote hidden}

--
FCC Rules Online at http://www.hallikainen.com
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2004\12\07@021839 by dr. Imre Bartfai

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Hi,

theoretically it is a sine-wave oscillator with a frequency of 0.2 Hz or
so. Actually it is hard to realize this way. However, with PIC it is a
simple task, because of you can mimic this by increasing a register by
time: 5000 / 256 would mean approx 20 i.e. increase a register by every 20
msec then decrease if 255. The modified register value is being written to
the PWM generator and here you are. A simple inverter could be used then
to drive the another pair of LEDs.

Imre

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On Mon, 6 Dec 2004, Ed Edmondson wrote:

{Quote hidden}

> ______________________________________________

2004\12\07@041524 by Alan B. Pearce

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>An 8 pin PIC with PWM output would do great!

>> My wife is making a ceramic light house for
>>a Christmas gift for her mother.

Lets see, four LEDs plus 2 power pins = 6 pins - sounds to me like an
application for a 10F :))))

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