Ten Stage Adjustable Staircase Generator - LM555, CD4017

Thread Starter

Sir Kit

Joined Feb 29, 2012
127
Can readers here please advise if there any design faults or ways to improve upon the attached circuit?

Will the CD4017 accept a 12V clock input directly from the LM555, so I can dispense with a 5V regulator?

In terms of the generated waveform, how does "my design" compare with the 74HC4150 version also attached?

Thanks for any pointers.
 

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AlbertHall

Joined Jun 4, 2014
11,952
Can readers here please advise if there any design faults or ways to improve upon the attached circuit?

Will the CD4017 accept a 12V clock input directly from the LM555, so I can dispense with a 5V regulator?
The invert output won't work. You need a resistor between it and the +12V supply.
The CD4017 probably won't work with a 12V supply and a 5V input signal. Supply the '555 with 12V and all will be well.
 

eetech00

Joined Jun 8, 2013
3,087
Can readers here please advise if there any design faults or ways to improve upon the attached circuit?

Will the CD4017 accept a 12V clock input directly from the LM555, so I can dispense with a 5V regulator?

In terms of the generated waveform, how does "my design" compare with the 74HC4150 version also attached?

Thanks for any pointers.
Don't forget bypass capacitors (0.1uf, 16v min.)

And you have to pull pin 13 low on the 4017 or the clock will be inhibited.

hmmm....there is no pin 17 on a CD4017...
 
Last edited:

Thread Starter

Sir Kit

Joined Feb 29, 2012
127
Thank you for your advice. The suggested changes have been made. I will see if there are any further responses to my thread, and then post the final version of the circuit here.
 

dl324

Joined Mar 30, 2015
14,303
Easier to read version of the image with a black background:
bw1.jpg
There's no easy fix to make the other one more readable...
 

Audioguru again

Joined Oct 21, 2019
4,523
When its supply is only +5V, the output high of the LM555 will be only +3.7V.
The CD4017 with a 12V supply needs a minimum input high of +8.4V so use the 12V supply also for the LM555. Adjust R3 to match.
Your "Invert" output will always be +12V.
 

dendad

Joined Feb 20, 2016
4,109
And why do you have C1 and C2 in series?
Did you intend for one cap to be from pins 2/6 and gnd, and the other from pin 5 to gnd?
 

Thread Starter

Sir Kit

Joined Feb 29, 2012
127
And why do you have C1 and C2 in series?
Did you intend for one cap to be from pins 2/6 and gnd, and the other from pin 5 to gnd?
The capacitors in series are the actual part values needed to create the 1-20Hz range.

I have attached a (white) copy of the current circuit that includes all the suggestions so far.

If I want more than 10 steps, is it possible to chain two CD4017's? What would be the relevant pin connections?
 

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dendad

Joined Feb 20, 2016
4,109
The capacitors in series are the actual part values needed to create the 1-20Hz range.
Ok.
But it seems to me to make more sense to use just one cap and select the resistors to suit.
Adding a bypass cap to the LM555 pin 5 is remomended too.
 

Audioguru again

Joined Oct 21, 2019
4,523
Repeat: The CD4017 does not have a 17th pin.

Your new INVERT output will have a voltage range from +6V to +12V and the NON-INVRT output from 0V to +6V.
Here is a simple AND gate for the cascading circuit:
 

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AnalogKid

Joined Aug 1, 2013
9,931
What is the value of the capacitor you intend to create with the combination of C1 and C2?

Note that the answers to both of your questions about the CD4017 are in the datasheet.

ak
 

Thread Starter

Sir Kit

Joined Feb 29, 2012
127
Thanks for the pointer to the data sheet.

The 17th pin on the CD4017 is a mistake in the DipTrace software footprint. Please ignore.

The series capacitance from LM555 pin 6 is just what works bench tested with the 1M pot to produce the desired frequency range.

I have added blocking caps and bias to the phase splitter which I believe will solve the problem of dissimilar voltages at invert and non-invert outputs.

Please see updated version of my circuit below. Any further assistance would be most welcome.

staircase_generator_v3.png
 

Thread Starter

Sir Kit

Joined Feb 29, 2012
127
Why?
Do you need the step amplitudes to be not even?
Yes, it would be good to have that option. Maybe to generate arb waves at some stage. Also I just prefer the casual feel of twiddling a pot. Kept me going for a long time while I learned what little I know about electronics.
 
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