CD4060 14 Stage Ripple-Carry binary counter Maximum Period.

Discussion in 'General Electronics Chat' started by Dritech, Oct 25, 2015.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Hi all,

    What is the maximum periodic time I can get at pin 7 (Q3) ?
    I need to obtain a periodic time of 60 seconds for the first pin (Q3). Is this possible?

    Thanks in advance.
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    (Edited)

    Q0 (not accessible) divides the clock rate by 2
    Q1 (not accessible) divides the clock rate by 4
    Q2 (not accessible) divides the clock rate by 8
    Q3 (not accessible) divides the clock rate by 16
    Q4 (is accessible) divides the clock rate by 32

    To get (1/60)Hz at Q4, the osc would have to run at 32*(1/60) = 0.5333Hz
     
    Last edited: Oct 25, 2015
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I think the OP meant Q4 (pin 7)

    To get 60 seconds out of a pin that has divided the input signal by 32, you would need an input of 60/32 seconds =

    image.jpg
     
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  4. eetech00

    Active Member

    Jun 8, 2013
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    Per the TI CD4060B datasheet:
    Q3 isn't accessible
    Q4 pin 7 is accessible (2^4)

    60sec/2^4=3.75
    If Cx = 4.7uF
    Rx = 3.75/(2.2*(4.7^-6)) = 362.669^3
    Rs = 10*Rx = 3.62^6
     
  5. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Thanks for the replies.
    Is there a limit that I should not exceed? and are there any limits for the resistor and capacitor values?
    On a site I read that the resistance should not exceed 1Mohms. Is this true since I so many schematics exceeding the 1Mohms.
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
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    From the TI datasheet (which looks like a scan of the original RCA datasheet):
    upload_2015-10-25_9-42-44.png
    upload_2015-10-25_9-40-43.png
    You can't believe everything you see on the internet. Many well intended folks post bad information...
     
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  7. eetech00

    Active Member

    Jun 8, 2013
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    Max Cx and Rx is supply voltage dependent but its on the TI datasheet
     
  8. DickCappels

    Moderator

    Aug 21, 2008
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    The resistor can vary over a wide range. If it is too small (a few KOhms) the output of the inverter has trouble driving it. The larger it gets, the more likely leakage in the capacitor and the '4060 input will cause a substantial error and/or drift in frequency. Generally, 10k to a few hundred k keeps life simple.
     
  9. JamesBond007

    New Member

    Oct 25, 2015
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    build it and see what happens.
     
  10. dl324

    Distinguished Member

    Mar 30, 2015
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    The NXP datasheet has the best description I've seen for RC timing; page 7.
     
  11. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    And many newbies keep repeating it, ad nauseum
     
  12. JamesBond007

    New Member

    Oct 25, 2015
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    The WWW is in colour. Believe everything you read.
    o_O
     
  13. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Thanks for the replies.
    I have another quick question. How can I 'pause' the circuit when a particular output is reached?
    For instance, I need to pause the circuit when Q8 turns high. I did try to connect a diode from Q8 to pin 11, but it did not work as expected.
     
  14. eetech00

    Active Member

    Jun 8, 2013
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    Maybe use a CD4020 counter instead of the CD4060, and a gated Schmitt oscillator?
     
  15. DickCappels

    Moderator

    Aug 21, 2008
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    Did you connect the anode to Q8 and the cathode to the Reset input, then add a 100k resistor from reset to ground so that the '4060 doesn't stay in reset all the time?
     
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  16. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Pausing a counter based on a direct connection to its own output is a logic bomb, because there is no way to unpause it without overriding the output. You need at least some steering diodes, and possibly a gate between the output and the oscillator input or enable input. For your application, what is the mechanism (external signal?) to unpause the counter?

    And to a previous point, not only is much innergoogle information unreliable, some of it is technically correct but incomplete without some experiencee or guidance. For example, the datasheet extract above indicates a max timing resistor of 20 M. That is an extremely high resistor value, and is based on the input stage device physics. It does not account for any leakage current around the input pin due to dust and finger oil and other contaminants on the chip and the pc board, and it makes for a very high circuit impedance that is more susceptible to external noise. And the biggie - capacitor leakage current. So 1 M is a common practical upper limit for the timing resistor, maybe more under controlled conditions. I've never seen or heard of success at or above 10 M.

    If this is a problem, and you're not married to the 4060, consider the CD4521. This is a 24 stage counter with the last 8 bits brought out. For the same range of output frequencies the oscillator is running 1024 times faster.

    ak
     
    Last edited: Oct 27, 2015
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  17. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Thanks for the replies. Since I already had the components for the 4060 available, I decided to build it on a protoboard.
    Unfortunately it did not work when using the attached schematic. From the calculations I made, the output at Q4 should have a periodic time of 120s. Is this correct? what can be wrong please?

    [​IMG]
     
  18. ScottWang

    Moderator

    Aug 23, 2012
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    Using the circuit to get 1 sec timebase as below and adding CD4518 or CD4520 to get the time you want.
    [​IMG]
     
  19. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    @ScottWang
    The op wants a 1 minute (60 second) output. Your timing will give him 32 second period out of Q4
     
  20. DickCappels

    Moderator

    Aug 21, 2008
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    @GopherT do you mean pin 14 (rather than pin 4)?

    By the way, I hope all understand that though power supply decoupling capacitors are not shown on any of the schematics thus far, they should be present in the physical circuit.
     
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