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#293 CD4060 RC Oscillator

Exploring the behaviour of the CD4060 ripple counter driven by an RC oscillator.



The CD4060 datasheet describes an RC oscillator configuration for self-driving the ripple counter. A 50% duty cycle is achieved when R1 = R2.


In this test I’m using R1 = R2 = 10kΩ, and C1 = 1nF. During charge/discharge, the equivalent resistance is 10kΩ|10kΩ i.e. 5kΩ, so the time constant for the rising and falling phases is 5µs (200kHz).

Thus for a near complete charge/discharge of 5 time constants, we’d expect an oscillation of around 40kHz. In practice, I’m measuring 38.7kHz .. so the approximation appears to be pretty close.

Here’s a trace of the oscillator (tapped at the net marked CH2 in the schematic):


The reset pin 12 should be pulled low to ensure stable operation. If left floating it can cause spurious results such as picking up 50/60Hz oscillation.

Ripple Counter

The CD4060 is a 14 stage ripple counter constructed of RS flip-flop units - see the functional diagram from the datasheet:


The input signal passes 4 stages before the first output is tapped (Q4). Thus the first (Q4) output signal divides the input frequency by a factor of 2^4

Stage 11 (Q11) of the ripple counter is also not exposed on a pin.

The lack of Q0-3 and Q11 is I think just pin economics so it all fits it in a DIP16 package.

The performance is summarised in the table and scope capture below.

Signal Scope Frequency (theory) Frequency (actual) Note
CH1 CH1 9.765Hz 10Hz = D7
CH2 CH2 40kHz 38.7kHz f-input
Q4 D0 2.5kHz 2.5kHz f-input/2^4
Q5 D1 1.25kHz 1.25KHz f-input/2^5
Q6 D2 625Hz 623Hz f-input/2^6
Q7 D3 312.5Hz 312Hz f-input/2^7
Q8 D4 156.25Hz 155Hz f-input/2^8
Q9 D5 78.125Hz 78Hz f-input/2^9
Q10 D6 39.06Hz 39Hz f-input/2^10
Q12 D7 9.765Hz 10Hz f-input/2^12
Q13   4.883Hz 5Hz f-input/2^13
Q14   2.441Hz 2Hz f-input/2^14






Credits and References

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This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.