If you're insistent on no micro-controller, I'd probably look for a 555 for
the osc and something like a 4017 for a counter, add a couple signal diodes
for the decode logic and Bob's your uncle.

Personally I think one of the tiny micros and three SOT23 transistors is a
better solution. (smaller, lighter, easier to change, etc) but, I too have
been in environments where _any_ software was to be avoided.

On Mon, Apr 3, 2017 at 12:15 PM, Dave Lagzdin <dtekk.com@gmail.com> wrote:

> I'd probably try playing  with an old cmos 4060 (and I forget the part
> number of the other one), has an oscillator and should find suitable
> outputs from the dividers
> D
>
> On 1 April 2017 at 20:30, CDB <colin@btech-online.co.uk> wrote:
>
> > I was chatting with someone from work the other day and the conversatio=
n
> > turned to them wanting to put an LED on their quadcopter which had a
> > strobing light similar to the navigation light on an aircraft, the one
> > that appears to make quick succession flashes that increase in frequenc=
y
> > making it look like one flash-pause pause next flash - pause -flash.
> > This would be easy to do with three LEDs in parallell, light LED 1 then
> > LEDs 1 and 2, then LEDs 1,2,3
> >
> > This got me thinking on how to hypothetically come up with a circuit.
> >
> > The criteria would be:
> >
> > No uP to be used.
> > Vcc =3D 5V
> > One white high brightness LED
> > Flash rate unsure but I suspect around 1 to 2 Hz
> > As few components as possible
> > Small footprint.
> >
> > Now as I tend to come up with complicated ideas and then work backwards
> > to simpler ones, I'm looking for comments and other ideas on what I hav=
e
> > thunked up so far.
> >
> > 1. The obsolete LM3909 might fit the bill (still available on Ebay)
> > except I need 3 flashes per period
> > (https://www.digchip.com/datasheets/parts/datasheet/321/LM3909-pdf.php)
> >
> > 2. CD4017/74LS90 decade counter + CD4093/74LS00 NAND gates for
> > oscillator + 1 74LVC1G27 single triple input OR gate chip connecting th=
e
> > decade counter outputs to the LED.
> >
> > 3. 74LS196 decade counter +  CD4046 PLL driven by  unijunction
> > transistor the idea being the frequency will change with the sawtooth
> > pattern and hence the light pattern will change.
> >
> > 4. CD4048 dual retriggable monostable + 555 as oscillator then OR the
> > two outputs together.
> >
> > 5 Pulse generator using an 74LS10  quad NAND gate + 555 as a clock
> > generator and OR gate at the two pulse outputs driving the LED.
> >
> > I've just thought, I suppose I could use a dual 555 timer + driver
> > transistor.
> >
> > I'm sure back in the 80s there were special one chip flasher chips aime=
d
> > at toys which did exactly what this circuit needs, but I threw my lovel=
y
> > paper based Maplins catalogue out years ago (1999 to be precise).
> >
> > Comments welcome.
> >
> > Colin
> >
> >
> >
> > --
> >
> > colin@btech-online.co.uk
> >
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> >
> >
> >
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