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Replace IC 4049

Discussion in 'General Electronics Discussion' started by colum, Jan 8, 2021.

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  1. bertus

    bertus Moderator

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    Nov 8, 2019
  2. colum

    colum

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    Jul 25, 2013
    The 4049 goes to the Transistors with 5V pulsing on each leg that had been 10 V but was divided by the 4027
     
  3. colum

    colum

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    Jul 25, 2013
    I may have an incomplete diagram, I do not see any and the role of capacitors are confusing at least for me
     
  4. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    You could also use IRL540 mosfets.
    Those are logic gate mosfets that are fully open at 5 Volt on the gate.

    Bertus
     
  5. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    Decoupling capacitors ate there to have a stable working of oscillarors and logic circuits.
    The 555 will need a 10 uF and a 0.1 uF accross the power lines.
    Also you need the capacitors on the 12 volts regulator to avoid oscillations from the regulator:
    3-pin_low_power_regulators_with_capacitors.png

    Bertus
     
  6. colum

    colum

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    Jul 25, 2013
    The supply starts off as 10 V and then is split with the CD4027 to 2 X 5V
     
  7. colum

    colum

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    Jul 25, 2013
    That is how its hooked up except that the 10uf is lower
     
  8. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    The 4027 will NOT divide the voltage , it will divide the frequency.
    The outouts will have the same amplitude as the powersupply.
    4027_function.png
    When used as a divider the outpouts will alternate at half the frequency.

    Bertus
     
  9. colum

    colum

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    Jul 25, 2013
    Thank you for that valuable information. I have decided to go back to square one and find a diagram that will drive a various speed synchronous motor
    I think I will beg someone in these forums to send me one
    Your advice is much appreciated...colum
     
    davenn likes this.
  10. WHONOES

    WHONOES

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    May 20, 2017
    One thing that nobody has mentioned is the very limited source / sink currents available from CMOS logic.
     
  11. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    The PDF in post #18 shows the driving specs of several chips.

    Bertus
     
  12. Frankchie

    Frankchie

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    Nov 14, 2017
    I wonder if the 4049 had proper bypass caps directly across its power pins.

    About 40 years ago I had a similar perplexing problem that drove me nuts for days. Out of desperation I added a 0.1uf bypass cap and the problem disappeared. As I recall I was using TTL logic chips, but I believe similar bypass caps are recommended for CMOS logic chips.
     
    bertus likes this.
  13. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    @Frankchie , That is why I mentioned the decoupling capacitors in post #21.

    Bertus
     
  14. Audioguru

    Audioguru

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    Sep 24, 2016
    The datasheet for the CD4049 shows that with a 12V supply its typical average output sink current is 25mA and its source current is 12mA per inverter. The circuit has 3 times those currents with the 3 inverters in parallel.
     
  15. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Recommended for any chip. No matter whether analog, digital, bipolar, MOS ...

    These bypass capacitors serve to supply an initial surge current when the chip's interbl transistors switch. This surge current canot be supplied very well by the traces of a PCB. Therefore the decoupling capacitors need to be placed near to the supply pins of the chip, ideally right next to the pin and need to be conneced to the supply voltages and ground (0 V) with traces as short as possible.
    In very high frequency circuits it is even customary to use different capacitors (e.g. 100 nF, 10 nF and 1 nF) in parallel to optimize the frequency response of the three.
     
  16. colum

    colum

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    Jul 25, 2013
    Thanks Harald I'm going to redo the entire circuit with more capacitors and more test points ...colum
     
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