Here's one alternative: Quad LED Fader 1 (QLF1)

Requires just 2 ICs (LM324), 4 transistors,16 resistors, 5 caps, 1 pot and
40 LEDs. That's 28 parts plus the 40 LEDs.

The circuit consist of 4 triangle waveform generators driving 4 current
sources. The LED current ramps linearly up and down and stays off for a
short time. Fade cycle time with R1/C1 shown is about 4 seconds as measured
on my breadboard. Adjust R1/C1 as required to the 4 independent frequencies.

I used just 3 LEDs to simulate the string of 10 but the result should be the
same. Slowly adjust P1 from 0V up to start oscillation and increase
brighness. Too high a P1 setting stops oscillation. You can lower R4 if
necesary if P1 adjustment is insufficient.


wilf

----- Original Message -----
From: "Bill Bigge" <wb23@...>
To: <beam@yahoogroups.com>
Sent: Thursday, May 22, 2003 10:12 AM
Subject: RE: [beam] Re: Slow pulsar


> The LED's are all going to be identical so there's no problem of
> matching - the bread boarded design I did drove 10 LED's fine so the
> behaviour is satisfactory. Some variability due to battery level and
> temperature isn't a problem, unless it gets to great.
>
> The alternative you suggested sounds good . . . I have no idea how to
> make the modifications though - any chance of a schematic . . . ;)
>
> bill
>
>
> -----------------
> Bill Bigge
> Autonomous Systems Lab
> Room 5A23
> Cognitive and Computing Sciences
> Pevensey-II
> Sussex University
> Brighton
> +44 (0)1273 877621
> -----------------
> <mailto:wb23@...> wb23@...
> www.cogs.susx.ac.uk
>
>
>
> -----Original Message-----
> From: wilf_nv [mailto:wrigter@...]
> Sent: 22 May 2003 17:53
> To: beam@yahoogroups.com
> Subject: [beam] Re: Slow pulsar
>
>
> Hi Bill,
>
> So be it: keep it simple.
>
> Here is some critique of the circuit.
>
> Driving LEDs in parallel requires careful matching of the LEDs or
> else some will be brighter than others. Add a small resistor in
> series with each LED. Do the LEDs have to be really bright (e.g. for
> daylight operation)?
>
> The driver circuit shown will change brightness with changes in
> supply volts and temperature.
>
> The ideal driver is a voltage controlled linear current source. (dV
> (IN)= dI (OUT)
>
> It is quite easy to make an improved circuit using 2 transistors With
> current sesning and feedback.
>
> regards
>
> wilf
>
>
> --- In beam@yahoogroups.com, "Bill Bigge" <wb23@c...> wrote:
> > Ok, I'm doing this for someone else and they've been quite specific
> > about the behaviour they want which is to have four sets of ten
> LED's
> > each fading on and off with different time constants (no
> synchronicity
> > between the sets).
> >
> > I've just refined the circuit I did and I think it's going to work
> > (schematic attached), I replaced the buffering inverter with a 2907
> > which allowed me to use smaller RC values AND I can produce four of
> > these circuits with one 74240.
> >
> > :)
> >
> > Bill
> >
> >
> > -----------------
> > Bill Bigge
> > Autonomous Systems Lab
> > Room 5A23
> > Cognitive and Computing Sciences
> > Pevensey-II
> > Sussex University
> > Brighton
> > +44 (0)1273 877621
> > -----------------
> > <mailto:wb23@c...> wb23@c...
> > www.cogs.susx.ac.uk
> >
> >
> >
> > -----Original Message-----
> > From: Wilf Rigter [mailto:wrigter@d...]
> > Sent: 22 May 2003 15:02
> > To: beam@yahoogroups.com
> > Subject: Re: [beam] Slow pulsar
> >
> >
> > For battery power I suggest using PWM.
> >
> > If you use 2 complementary modulated current sources you can drive
> 5 +5
> > LEDs in antiphase so that 5 wax as the other 5 wane. More
> interesting
> > effect and comes practically for free.
> > If you can handle multiple of 3 LEDS (9 or 12), why not use the
> > "spectrummer 4" circuit (optimized for your application), which
> would
> > give
> > the appearance of light rippling along the string with the speed of
> > movement
> > controlled by the light level. Looks like a lot of bang for the
> buck.
> >
> > wilf
> >
> >
> > ----- Original Message -----
> > From: "Bill Bigge" <wb23@c...>
> > To: <beam@yahoogroups.com>
> > Sent: Thursday, May 22, 2003 6:34 AM
> > Subject: [beam] Slow pulsar
> >
> >
> > > I'm trying to put together a simple circuit to fade a string of
> LED's
> > on
> > > and off slowly. It needs to drive ten LED's in parallel and turn
> them
> > > on and off slowly to give a nice slow pulsating effect, all
> running
> > off
> > > a 3v supply (2x AA batteries).
> > >
> > > So far I've got a circuit consisting of a suspended bicore that
> > outputs
> > > through an inverter to a resistor capacitor circuit to the base
> of a
> > > 2222 that drives the LED's. To get the desired effect I had to
> use a
> > > 2200uf capacitor and a 1k resistor in the RC circuit. With a
> smaller
> > > cap and a larger resistor there isn't enough current to drive the
> > > transistor properly so the LED's are very dim. This big capacitor
> > makes
> > > the whole thing bulky and I think I've got a less than optimal, or
> > > elegant, solution.
> > >
> > > Any suggestions for an alternative. . .
> > >
> > > Bill
> > >
> > > -----------------
> > > Bill Bigge
> > > Autonomous Systems Lab
> > > Room 5A23
> > > Cognitive and Computing Sciences
> > > Pevensey-II
> > > Sussex University
> > > Brighton
> > > +44 (0)1273 877621
> > > -----------------
> > > wb23@c...
> > > www.cogs.susx.ac.uk
> > >
> > >
> > >
> > > Yahoo! Groups Sponsor
> > >
> > >
> > >
> > > To unsubscribe from this group, send an email to:
> > > beam-unsubscribe@egroups.com
> > >
> > >
> > >
> > > Your use of Yahoo! Groups is subject to the Yahoo! Terms of
> Service.
> > >
> >
> >
> > ---
> > Outgoing mail is certified Virus Free.
> > Checked by AVG anti-virus system (http://www.grisoft.com).
> > Version: 6.0.478 / Virus Database: 275 - Release Date: 5/6/2003
> >
> >
> >
> > Yahoo! Groups Sponsor
> >
> >
> <http://us.a1.yimg.com/us.yimg.com/a/ya/yahoo_autos/ifsbolrec2.gif>
>
> >
> > Select Make Acura Audi BMW Cadillac Chevrolet Chrysler Dodge Ford
> GMC
> > Honda Infiniti Jaguar Jeep Lexus Lincoln Mazda Mercedes-Benz
> Mitsubishi
> > Nissan Pontiac Porsche Toyota Volkswagen Volvo Other
> >
> > <http://us.adserver.yahoo.com/l?
> M=253930.3294222.4590862.1261774/D=egrou
> > pmail/S=:HM/A=1408257/rand=852291987>
> >
> > To unsubscribe from this group, send an email to:
> > beam-unsubscribe@egroups.com
> >
> >
> >
> > Your use of Yahoo! Groups is subject to the Yahoo!
> > <http://docs.yahoo.com/info/terms/> Terms of Service.
>
>
>
> Yahoo! Groups Sponsor
>
> <http://rd.yahoo.com/M=249982.3179269.4495679.1261774/D=egroupweb/S=1705
> 948923:HM/A=1524963/R=0/*http://hits.411web.com/cgi-bin/autoredir?camp=5
> 56&lineid=3179269&prop=egroupweb&pos=HM>
>
> <http://us.adserver.yahoo.com/l?M=249982.3179269.4495679.1261774/D=egrou
> pmail/S=:HM/A=1524963/rand=791334220>
>
> To unsubscribe from this group, send an email to:
> beam-unsubscribe@egroups.com
>
>
>
> Your use of Yahoo! Groups is subject to the Yahoo!
> <http://docs.yahoo.com/info/terms/> Terms of Service.
>
>
>


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.483 / Virus Database: 279 - Release Date: 5/19/2003