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Re: Traffic Light Electrical Circuit

To: Ronald Olds <>
Subject: Re: Traffic Light Electrical Circuit
From: Randall <>
Date: Sun, 31 Oct 1999 16:58:55 -0800
Ron :

There is a neat little timer IC that works quite well for what you want,
called the NE555.  (There are lots of variations, including two or four
timers in a single package.)  I built a 'light chaser' many years ago
using them, and it worked out quite well.  Basically, you set up a 555
timer per light, wired as a monostable, and connect each output to the
next input so that when the first one expires (and turns the light off),
the next one trips.  One of the nice things about the 555, it's output
driver will source enough current to drive a triac or 12vdc relay, so
you can still use 110vac lamps if you want.  Plus, building your own
lets you do things like adjust the 'on' times individually, which you
usually can't do with commercial light chasers.

Use your favorite web search engine for "555 timer circuit", I'm sure
you'll find something useful.  I found a good start at .  Note that the
trigger switch can be replaced by a 0.1 uF capacitor back to the
previous stage, and R1 can be a variable resistor to allow for
adjustment.  (You'll probably still want one trigger switch, to start
the whole mess, or wire a 4th 555 as a retriggerable astable with a much
longer time constant, to start automatically.  You could even make it
the master, to give some off time between cycles.)

There are also lots of basic electronics books available on the
subject.  Try, your local library, or Radio Shack (who will
also have 555s).

I've tried doing the same thing with thermal 'time-delay' relays (having
each one start the next one), but it never worked very well.  The relays
are also a lot more expensive.


Ronald Olds wrote:
> Hello Listers (or should  say BOO!! tonight),
> I have obtained a traffic light, actually one of the small european types,
> and would like to use it as a display in the family room. Can anyone out
> there help me with a schematic that would allow the lights to flash in
> sequence. I know I can use separate timer relays and adjust each light so
> they turn on and off in what looks like the correct sequence but I was
> hoping for a circuit that would sequence each light in order. I have to
> rewire the lights from the original sockets so I can use 110V or even 12v
> for the supply.  I'll appreciate any suggestions I can get.
> Thanks,
> Ron Olds

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