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i need help with my monostable circuit!!

Discussion in 'General Electronics Chat' started by toh liu wang, May 3, 2017.

  1. toh liu wang

    toh liu wang Member

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    When the motor is directly connected to the 9V power supply, it works fine.
     
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

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    I talked about the current of the power supply or battery. If it cannot supply enough current then its voltage will drop until the circuit will not work.
    The relay is a 5V one, not a 12V one.
     
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Since the motor works fine when powered by the 9V power supply then the relay or its driver does not work. Does the 9V battery power the motor properly?
     
  4. dave

    Dave New Member

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  5. toh liu wang

    toh liu wang Member

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    Yes. The 9v battery powers the motor properly.
     
  6. toh liu wang

    toh liu wang Member

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    However with relay and motor, the voltage dropped drastically.
     
  7. toh liu wang

    toh liu wang Member

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    the circuit did not work for me ;(
     
  8. toh liu wang

    toh liu wang Member

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    motor still won't stay on.
     
  9. toh liu wang

    toh liu wang Member

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    can i remove the relay? And just plug the motor straight to the IC? How do i make sure the IC doesn't burn?
     
  10. toh liu wang

    toh liu wang Member

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    The motor stayed on for awhile before switching off but not for long. The 555IC did not burn as well.
    But after the third try, the motor did not stay on, maybe i need a stronger power supply and larger R1 to make it stay longer?
     
  11. toh liu wang

    toh liu wang Member

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    if i replace it with a led, the led stays on for a long period of time maybe near 2mins?
    But when i replace it with motor, it stays on for few seconds before turning off.
    I think the current usage of the motor is pretty high.
     
  12. toh liu wang

    toh liu wang Member

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    what if i change my motor to a 6V motor?
     
  13. toh liu wang

    toh liu wang Member

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    it worked now!!! i used a 9v power supply and not that weak battery! it turns off after 5mins though...
     
  14. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Timing parts that are 51k and 470uF produces a timeout of 26 seconds. (51k x 470uF= 24 x 1.1= 26.4 seconds but the tolerance of the capacitor might be -20% and =50%).
    Maybe your 555 is connected wrong or is blown up.
     
  15. alec_t

    alec_t Well-Known Member Most Helpful Member

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    If the 470uF cap is leaky it will take longer than predicted to charge up. That would explain the 5mins time-out.
     
  16. toh liu wang

    toh liu wang Member

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    Thanks. I'll get the capacitor and IC changed and see the difference.
     
  17. toh liu wang

    toh liu wang Member

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    i realized when i remove the capacitor from pin 8, the LED stays on for 27 seconds.
    When the capacitor is in the circuit, the LED stays on even longer
     
  18. GromTag

    GromTag Active Member

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    Just general experimentation can get results, just note that not all IC's can have their signal pins directly connected without resistance of some sort.

    :the Chip or objects Datasheet is an important piece of documentation:
    Tho some datasheets have had errors within the data therein.

    And also in thought on "typing moment of" as in thoughts being typed can seem quite a bit requirement of dechiphering of whats going on when doing multiple things. An Ideal point that I do not seem to grasp very well is to single out any project and state direct view...

    Even tho with any advice or concept of direction, gaining a sense of what and where with anything electronic is and will be time consuming.


    Use your own pace even if it leads to exasperation is one phrase I still hear to this day.
     
  19. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The datasheet of an LM555 says that a capacitor from pin 8 to pin 1 is important (it provides supply power to the 555 when the 555 output is switching and drawing a 400mA current spike). The minimum supply for an ordinary 555 is 4.5V so its 400mA current spike plus the high startup current of the motor might cause the supply voltage to drop lower than 4.5V without the capacitor.
     
  20. toh liu wang

    toh liu wang Member

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    Hi im just wondering why wont my monostable go off?
     
  21. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Perhaps your timing cap is excessively leaky or is shorted.
     

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