I built a 16 step sequencer using two cascading 8 step baby sequencers based on this schematic. (See the thread here.)
I wanted it to have selectable step count, so I installed a rotary switch connected to the “RESET” on the schematic.
However, it works strangely:
Up until 7 steps: it works without problem.
If set to 8-15 (N) steps: after the Nth step the first IC is reset, waits a step, then starts counting again. The second IC is not reset and finishes the “16 step” sequence, so both ICs run in parallel until 16, then the cycle restarts.
If set to 16 steps: the sequence runs once, then stops at step 1.
I tried troubleshooting the stuff but haven’t found the issue. Do any of you have a tip where did I mess up?
Nowhere, this is exactly the expected behaviour from the schematic. I don’t know why that line is labeled ‘reset’, but it does not work they way you (or anyone seeing a line labelled ‘reset’) would think.
This daisy chained approach works by having one counter run until its last step, then disabling itself and resetting the other. The mechanism you implemented does the resetting of the first IC, but not the disabling of the second one.
The disabling at step 16 and the waiting of one step can be resolved by AC coupling the reset input (put a 100nF cap in series). The disabling is slightly more involved. I think you can fix it by adding a flipflop that’s trigged by the reset input or Q8 of the first IC. This will then keep pin 13 of the second IC high until it is reset. I’m sure there’s a schematic somewhere out there which already has this added.
I think I’m getting there but still got work to do. Now, the second IC stops after one step. I think that’s something to do with the AND gate. I’ll use a multimeter to measure the inputs.
Also, what resistance did you use for the output?
Fast forward to two and a half years later: I managed to build a working 16-step baby sequencer. Thanks for all your help!
After being unable to correct the issue, I put this project on hold, and just used the previous build as a Baby8. But fixing the issue has always been on my list. I recently gathered the courage to ramp-up the sequencer. Which meant gutting the box and scrapping the boards. I built new boards designed around the schematics above (with the AND gate). I also redesigned the step count part: now it can run 1-16 steps. And I also built a new enclosure with a new front panel. So basically: I built a new device from ground-up. That fixed the problem! (Okay, I saved panel-mount components, which is great, becauce that’d be a lot of wiring.)
Thanks again for your help! Compared to the time of my first try, I now understand a bit more about how these things work; this forum is one of the reasons why.
