Blinking LED circuit

[david at thekramers.net (David Kramer)]

On Fri, 24 Sep 2004, Doug Sweetser wrote:

> Hello:
> 
> I need a pair of red blinking LEDs for a video project, one where the
> first blinks, there is a 0.5 sec gap, the second one goes, then a 3.5
> second gap, and then that cycle repeats.
> 
> In an hour of Google time, I can see how to get one blinking light,
> and a pair at two different frequencies.  I need a pair of lights at
> the same frequency, but displaced by a bit of time.
> 
> Perhaps the easiest thing to do is make a pair of single blinkers,
> hook them to the power supply independently, and do that until the
> blinking pair looks good.
> 
> If this is easy/fun for any EE folks in the audience, I would like to
> hear from you.

This isn't the way that many would go about it, but I would use a 4017 
decade counter.  A decade counter is a chip with 10 outputs, and it puts 
each one high in turn, from 0 to 9, then optionally starts over again.

http://www.doctronics.co.uk/4017.htm

I would do it this way because you may decide, after looking at what it 
can do, that you want to do something completely different, and this chip 
can be used to make all sorts of patterns.  To do exactly what you want, 
just connect LED's to 1 and 3 or 4, and you might get the effect you want.

Or you can use a standard flip-flop circuit
http://www.doctronics.co.uk/4013.htm

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DDDD   David Kramer                   http://thekramers.net
DK KD  Math is pure science.
DKK D  Physics is noisy math.
DK KD  Chemistry is smelly physics.
DDDD   Biology is squishy chemistry.