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Making a sequencer with a 4017 will work fine if you want 10 or less steps (say 4 or 8). 4017s can be cascaded, but it is not what we are thinking of as cascading. We expect it to work as follows:

Proper sequencer count to 16
LEDs light up from 1 to 16 and repeats. Our idea of 16 steps.

Cascaded 4017s count to 16
In reality cascaded 4017s would light up 1 to 10 and then the 11th LED would light up and stay on. 1 to 10 would light up again, and then when it got to the 10th LED again the 12th LED would light up and stay on (11th would go off). This would continue to repeat. The 4017s idea of 16 (10+6) steps.

Cascaded 4017s work 100-10-1
Another way to look at this is that each 4017 represents a column in a base 10 number system (Ones, Tens, Hundreds, etc). All 4017s are always running. Only the first 4017 has an actual CLK signal connected (10 pulses to complete one 10 step cycle). Cascaded 4017s get one pulse for every 10 pulses the previous 4017 got. Cascaded 4017s are connected through the "carry out/ carry over" pin (12).

The phillips datasheet shows another more elaborate hookup than just using the carry out pin. This alternate hook up still follows that only one 4017 is getting a CLK signal fed straight in, and all other 4017s get a "CLK signal" from the 4017 before them.

Shared clk signal = parallel
Splitting a CLK signal between 4017s will make the 4017s run in parallel. All will light up the same LEDs at the same time.

The follow are some of the results I had from testing splitting/sharing CLK signal and trying to disable one or the other 4017.

    Removing CLK sig left the last step/beat H.
    Removing RST left o0 H.
    Putting RST High left o0 H.
    Disconnecting GND or V+ left last step/beat H.
    ENABLE has to be L or o0 will be H.
(H=High=1, L=Low=0. If an LED is left on (H) it also means a trigger is still on/active.)

So pretty much trying to use two 4017 chips and send a signal to one of the two leaves the "non-used" 4017 with a H on one of the steps/beats.

4017 pinout



cappy@sailormouth.org