[sdiy] 10 step sequencer

[Peter Grenader]

Tim Parkhurst wrote:

> You could also use a multiplexer chip (available with 8 or 16 outputs)
> driven by a 4 bit binary counter. For each clock pulse to the counter, the
> binary count will advance once and select the next output on the
> multiplexer.

Trade secrets withstanding, this is how Milton handles it.  A serial 30ms
pulse going into a 4516 then into two 4051s.  'course, you could use one
4067 instead of two 4051s (that's a single 16 step multiplexer instead of
two cascaded 8 steppers).

As far as the short input pulse - it's the best way to handle counting as it
prevents unwanted oddball logic states from popping up from multiple inputs
active at the same time when you don't want them, which you don't as they
are a bitch to troubleshoot unless you have an elevendy-million channel
scope that's faster than a Saturn V..

As far as the short output pulse, you're going to have to make that happen
as the counter outs will stay at logic 1 for the duration of the time each
given stage is active.  You want it this way, unless you want the voltage at
your pot to disappear before the next stage fires up.  Just run the stage
output to a one shot, or through a couple of npns with an R/C tied to the
base of the first (determines the pulse width you're after) and the second
used to put it back into phase with the counter.

You're gonna have to bump up the drive of the counter  if you're planning on
more than one bank - an 4050 or a tranny for each output will do the trick
nicely.

Word of warning from the initiated:  If you are planning on breadboarding
this, do yourself a favor and lay out the multiplexr/counter pair as close
as possible to one another physically to keep your wire length as short as
possible. Also try to limit any wires coming to both from crossing over each
other.  I know, I know - tall order.  But counters are like racehorses at
the line.  They sit there waiting for the slightest little pulse to take
off.  Crossed unshielded wires can set them off.  Been there, done that.

hope this helps,

Peter