[sdiy] 4017 sequencer

[Paul Maddox]

Pat,

> I've gave it 30 seconds of though while I got a snack, and maybe I figured
> out the problem.  Could it be that I can't just tie reset to an output,
and
> expect it to end/loop at that step, without also removing the ouput?  So I
> would need a 2P8T switch instead?

as Niklas said, if you want 2 steps, you tie the reset to the 3rd stage.
In theory the rest pulse should be VERY quick and shouldn't hear any CV from
the 3rd stage.
It looks like you've done that, but I can't be sure as the diagram is a
little 'squished'.

Somethings to consider,

1) I would take the LEDs out of the CV loop, and use a transistor to turn
them on.
2) I'd add a pull up resistor on the reset circuit (10K or so) to prevent
resets whilst changing step (when the reset line will be floating).
3) add a pull up resistor on the clock and enable input for the same reason
as above.
4) add a unity gain buffer to sum all the voltages from the wipers of the
pots, as it stands at the moment, the pots are all affecting each other and
hence the output impedance and potentially the stability of the output CV.
5) if you do (4) then you'll need to replace the 1K pots with 100K pots, and
use something like a 10K input resistor for the summing opamp.

Just a few thoughts
Paul

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