Odp: [sdiy] ...dumb question (CD4017 sequencer)

[Roman]

A) IMHO sequencer always puts out some voltage. Even if it's 0V, it's still a
valid voltage, especially
when your sequencer would generate voltages in, say, +/-5V range.
But you can simply clamp the output with transistor driven from STOP
input/button. To let it generate
voltage for duration of 1 step, so it won't shut up in the middle of the step,
simply drive 4017 clock
input via AND gate, and its second input connect to a flipflop that defines
run/stop mode. Then there's
D-flop (4013). Its clock is fed from same source as 4017, D input is driven by
run/stop mode flipflop.
So the otput will change only on clock edge, after stop condition. This D-flop
can then controll the
clamping transistor mentioned earlier.

B) make trigger pulse out of Start button/input, that feeds MR input of 4017
(pin 15). That will
reset it to first step.

----- Original Message -----
From: Electronium
To: Synth DIY
Sent: Monday, September 30, 2002 8:52 AM
Subject: [sdiy] ...dumb question (CD4017 sequencer)


OK, here comes my first kinda dumb question (of many more to come, I'm sure) for
the list...

I'm building a very simple 8 step/2 stage sequencer, using a CD4017 and here's
what I can't quite figure out:

How do you get the sequencer to stop so that it - A) does not put out the
voltage of the current step and B) always starts again on step 1, when you
restart it?

I have read the datasheet & messed around with the clock enable input, reset, &
clock input... but I just can't quite get it to do what I want.  I am building
this for a simple synth project (inside an old samsonite suitcase) and I want it
to act as the master clock to control (start/stop) other modules also.

I should also mention that I am trying to keep all of the modules in this
project as simple as possible.

Any ideas?

Regards,
Mike Brown

(BTW... I suppose, actually, that my question about the SN76489 a few weeks ago
was really my *first* dumb question ; )