"Bill Bowden" wrote in message
oups.com...
Peter Michelson wrote:

As I said, I would like to cycle among three LEDs.
To elaborate: one LED is turned on at any given time;
each time I depress the momentary switch, I would like
the LED that is on to turn off, and the next LED
in sequence to turn on;

There is a "10 stage LED sequencer" at the below address.
You will need to change the 555 oscillator into a
555 "one shot" circuit so you can use a pushbutton.
The 4017 can be used for just 3 LEDs by connecting the
reset line (pin 15) to the 4th output, (pin 7).

http://ourworld.compuserve.com/homep...htm#4017-2.gif

-Bill


First question: can I use more than one stage of the LED sequencer to
prolong the duration of an LED being on? For example, if I want the first
LED to stay on twice as long as the 2nd and 3rd LEDs, is it sufficient to
connect the first two outputs to the first LED, and then only one output to
each of the other two? In other words, is it a problem to connect two
outputs together without using diodes?

Second question: I have decided to use the approach you recommended (using
the 4017 with transistors to boost the outputs, as depicted in the link
above). In order to drive the process, I would like to use a combination of
the simple toggle provided he
http://www.terrypin.dial.pipex.com/I...-Momentary.gif
and the 555 for automatic operation. In other words, I would like to be
able to switch back and forth between using a momentary switch to control
the LEDs and using the 555 to automatically cycle through them.
Could someone please explain the circuit design necessary for switching
back and forth between the two?

Third question: Alternatively, since the 555 can be used as a debouncer by
itself, is it possible to configure the circuit so the 555 could actually be
used both as a debouncer for manual operation and as a timer (which would
obviate the need for the simple toggle above)?

Fourth question (I think I've well exceeded my quota here): is there any
good freeware or open source software for designing circuits and printing
out those designs?

Thanks a bunch,
Peter