Baby 16 sequencer step count issue

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.

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Oh now, that’s bad news. Thanks for the information!
Is it possible to overcome this issue, disabling the second IC somehow?

yeah I was thinking on how to fix it.

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.

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Thanks!
I’ll try the AC coupling for sure. The fliplop I don’t fully understand yet but I’ll look up the schematic you mentioned.

I think you need also an AND GATE (with diodes) between the 2 ICs, like this :

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for the Reset circuit look at this :

btw it’s write “not verified” but it’s old and i’ve just verified it yesterday, all works fine :wink:

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Thanks, Dud, I will try these one too!

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keep us informed of your evolution

I’ll definitely post an update once I get this working.

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You are maybe already into this one, else you could go for a binary counter like CD40193 (or simpler) and a CD4514 decoder to get a 16-step sequencer.

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I may try building a sequencer like this in the future, thanks!

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?

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maybe something wrong here

2 cd4017 - Copie

for the output resistor, i only put a 1k after the buffer output opamp