4017 counting and switching the 4066

Thread Starter

NOISEBOB

Joined Jul 7, 2019
37
Hi
i don't think i fully get it, but this is how i imagine it would be possible to make a 4-step sequencer that i can run any signal source through:stepping.png

i'd take a clock signal from a slow 40106-based oscillator to run the 4017.
the four signal outputs would be mixed to one master output in the end.

the schematic there is just a quick and dirty write-up..



i'm sure the counting circuit part could use some fixing, like adding pull-down resistors on Q5 to Q9... right?


besides that, am i completely off or does this make any sense?
 

JohnInTX

Joined Jun 26, 2012
4,344
Looks OK for the most part. Standard caveats apply for decoupling the power supply etc.
You don't need resistors on the extra outputs.

4066B has lower ON resistance.

Have fun!
 

Thread Starter

NOISEBOB

Joined Jul 7, 2019
37
Looks OK for the most part. Standard caveats apply for decoupling the power supply etc.
You don't need resistors on the extra outputs.

4066B has lower ON resistance.

Have fun!
i just learning to get the point of pull-up/down resistors and i hardly know what decoupling is about, but you mean something like this?
stepping2.png

I think it will work. You shouldn't need the diode on Q4, or resistors on the unused outputs.
because there is no need to pull anything down as when the counter reaches Q4 it goes back to Q0 and counts anew, yes?



Hello there :)

Why are you using a Tri-State analog switch.
tri-state? i don't know.. mostly because i have access to 4066 chips....

:)
 

Audioguru again

Joined Oct 21, 2019
2,088
The analog gates are not tri-state. They are simply on passing the signal or they are off.

The input signals must be within the power supply voltages of the CD4066, not capacitor-coupled.
ALL CD4066 ICs are B.
 

ElectricSpidey

Joined Dec 2, 2017
1,336
I only use a diode in the reset net if I'm also using a RC power up reset circuit, I use those in my circuits because 4017s have a nasty habit of starting on output 1 instead of 0. (and other random outputs)
 

JohnInTX

Joined Jun 26, 2012
4,344
i hardly know what decoupling is about, but you mean something like this?
Yes. A small capacitor across each IC's power pins is good practice.

To understand what is going on here is a grossly simplified discussion:
When the CMOS logic switches, it requires a short but large pulse of power (compared to its static state).
The sudden current demand needs to be serviced from the power supply through wires, board traces etc. The connecting wires have a little inductance that at the frequencies generated by the switching, resists the sudden increase in current through them. So just as the CMOS IC demands more current, the wiring conspires to briefly limit the current available. The result can be a drop in the voltage at Vdd at switching just when the chip needs it most. That can result in erratic operation of the CMOS IC.
A capacitor wired close to the power pins provides a local source that can supply the chip during the immediate switching current demands of the CMOS IC.
The type of capacitor is important. It must be able to supply current quickly meaning low internal impedance. Ceramics are the usual first choice. They are frequently paralleled with a bigger capacitor like a small tantalum. The idea is that the ceramic services the immediate current demand from the switching CMOS. The slower but bigger value tantalum helps out but primarily is to recharge the ceramic after the draw. On a large board, you will frequently see a ceramic on each IC, a tantalum across the power bus shared by a few ICs and larger aluminum electrolytic(s) scattered around to provide a slower but bigger source to help recharge the tantalums.
Because the capacitors provide local sources for switching currents, the power lines don't see the high frequency surges which reduces the effect of their inductance. The power lines are 'decoupled' from the high frequency switching currents. That's important when the power lines service many circuits/boards in a system.

Each circuit will have its own needs but a .1 ceramic in parallel with a 1uF tantalum is my personal starting point at each IC.
 
Last edited:

Thread Starter

NOISEBOB

Joined Jul 7, 2019
37
I only use a diode in the reset net if I'm also using a RC power up reset circuit, I use those in my circuits because 4017s have a nasty habit of starting on output 1 instead of 0. (and other random outputs)
Oh, good to know... in my case it doesn't matter
Yes. A small capacitor across each IC's power pins is good practice.

To understand what is going on here is a grossly simplified discussion:
When the CMOS logic switches, it requires a short but large pulse of power (compared to its static state).
The sudden current demand needs to be serviced from the power supply through wires, board traces etc. The connecting wires have a little inductance that at the frequencies generated by the switching, resists the sudden increase in current through them. So just as the CMOS IC demands more current, the wiring conspires to briefly limit the current available. The result can be a drop in the voltage at Vdd at switching just when the chip needs it most. That can result in erratic operation of the CMOS IC.
A capacitor wired close to the power pins provides a local source that can supply the chip during the immediate switching current demands of the CMOS IC.
The type of capacitor is important. It must be able to supply current quickly meaning low internal impedance. Ceramics are the usual first choice. They are frequently paralleled with a bigger capacitor like a small tantalum. The idea is that the ceramic services the immediate current demand from the switching CMOS. The slower but bigger value tantalum helps out but primarily is to recharge the ceramic after the draw. On a large board, you will frequently see a ceramic on each IC, a tantalum across the power bus shared by a few ICs and larger aluminum electrolytic(s) scattered around to provide a slower but bigger source to help recharge the tantalums.
Because the capacitors provide local sources for switching currents, the power lines don't see the high frequency surges which reduces the effect of their inductance. The power lines are 'decoupled' from the high frequency switching currents. That's important when the power lines service many circuits/boards in a system.

Each circuit will have its own needs but a .1 ceramic in parallel with a 1uF tantalum is my personal starting point at each IC.
Thank you so much for this. It makes total sense now.

...

I breadboarded my idea here, it works like a charm, kind of... I used a 4093 to generate a short pulse to trigger the 4017 to count. step 1 was fed into the 4066 switch to which I connected a 40106 oscillator..

I didn't do any pull down on the unused pins on the 40106, which I suppose is why I could hear the oscillator bleed through when the counter was at step 2, 3 and 4...
 
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