Hi- I tried to post this in the forum, but apparently i can’t do math.
from an email:

Re: VoS Sequencer – 2 cascading 4017s?

I want to build a 16-step sequencer. I’ve seen some info on cascading 2 4017’s togethere here: http://experimentalistsanonymous.com/board/viewtopic.php?t=1417&sid=49b2164a18e99cfdae1c0e9d8d4caf7a

What i want to know is, how hard to you think it would be to modify your "bare bones kit" to accomodate a 2nd 4017?

thanks!

-justin

Chaining the sequencer’s together would require some non-trivial circuit mods. The 4017 decade counter was chosen because of how easy it was to use and how cheap it’d be to produce the kits. To chain 2 together you have several options. First, you can make 3 seperate sequencers. One of these will control which of the other two is activated. Shorten the steps of the control seq. to 2 by inserting a patch from the 3rd step’s gate output to the reset jack. This will play a 2 step sequence. To clock this control sequencer, you need the signal from the last step of each of the other 2 seq’s. This means that when one seq finishes, it will send a signal to the control seq to advance a step. Now, the last part (note, I haven’t tried all this myself yet), connect the clocks of the 2 sequencers together. slaving one to the other. You will need to modifiy the clock on/off signal to allow it to be patch in externally. Then connect the output of step 1 of the control seq to the clock enable of the first seq. Similarly connect the output of step2 of the control seq to the clock of the second seq.

That’s kinda messy, but it should work. The cleaner option would be to alter the internal circuitry. There is information on chaining 4017s on page 5 the datasheet:

http://focus.ti.com/lit/ds/symlink/cd4017b.pdf

You would need to add a CD4001B to get the NOR gates necessary to make this work. not very difficult, but you’d probably have to cut a few traces on our circuit board.

Hope this helps.

-Travis

More options…

The trouble with chaining two of them together is that even if you could get one to pause while the other was moving, it would still have an output on. To get around this, you’d need to either use a transistor to cut the power to the whole chip or not use all the outputs, as described in this great pdf.

To summarize how it works, the 10th step of the first 4017 is connected to its own clock inhibit input. So when the 10th step is reached, it stops. The 10ths step is also connected to a NAND gate that turns off a clock inhibit on the 2nd 4017, which has been pausing in the 1st position (not connected to the output). So the 10th step actually comes from the 2nd position on the 2nd 4017. When the 2nd 4017 reaches its 10th step, it connects to the same nand gate to turn itself off, and also to the rest on the first 4017.

You’d need a bunch of diodes or some switches as shown here to combine the signal in the end. Also, you’d have to figure out a way to reset all the chips when everything is first turned on since they don’t start in a known state.

-scott

thanks guys!
So let me see if i got this-
Going by that epanorma pdf-
If i only want 16 steps, i can omit that third 4017 and disconnect the inverter (IC4-b). I’ll just keep the 2nd input on the NAND gate high. And then connect the 17th output of the sequence (pin 6 on the 2nd 4017) thru an inverter, and then on to the first 4017’s enable pin- also connected to the 1st input of the NAND which then disables the 2nd 4017, and the whole cycle will start over. Does that sound right?

And about reseting the chips- this pdf suggests putting a cap between the V+ and all the reset pins.

-justin

great link to that other pdf. I don’t quite get how C1 resets everything, it seems like pin 11 of the third 4017 could hold the reset line low even while power is applied. I think your plan sounds good, let us know how it turns out!