[sdiy] 4017 sequencer

[Roy J. Tellason]

On Friday 31 December 2004 04:46 am, Pat Kammerer wrote:
> Hi all,
>
> I've been working on a little 8 step CV sequencer project, and I'm getting
> odd results.
>
> Here is the schematic;
> http://www.wearerecords.com/temp/4017_8step.jpg
>
> As you can hopefully see(sorry for the bad schematic), I am attempting to
> use the reset and a 1P8T switch to chose how many steps are used.  Another
> switch SPDT, enables or disables the chip.

One thing about CMOS parts,  is all inputs need to go somewhere,  all the 
time!  Given that,  what I'd do in a situation like this is to use a SPST 
switch where you have that SPDT,  and a resistor to the level you want when 
the switch is open.  Similarly have a resistor going from the clock input to 
either ground or Vdd.  It doesn't take much of one,  100K will work fine. 

> After much trouble shooting, I've gotten rid of any errors that I could
> find, and still there is an issue.  S1 works when it's selected for 1-4
> steps, but jams on 5 when selected to run 5-8 steps.  When stuck at step 5,
> it seems that ALL of the pots effect the CV that is output.
>
> If anyone can help me, with the information that I've given, I would be
> very thankful.  It already makes a really fun 1-4 step sequencer, so I
> really want the whole project to work.

That sounds really odd.  Either the switch isn't quite doing what you think it 
is,  or there's a wiring error someplace.  I hope the 4017 is socketed.  If 
so,  pull it out and trace out what's going on with an ohmmeter,  I suspect 
it's not quite what you think...