555 monostable timer, pulsed LED and buzzer motor

Discussion in 'Analog & Mixed-Signal Design' started by dMEK, Apr 8, 2019.

  1. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    With RV2 at zero, the R5/C2 time constant is applied to the motor drive so the motor speed will ramp rather switch.
    I don't know what the effect of 220uF on the Q pin of the '555 will have on the chip function.
     
  2. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    That's the reason why ...
    ak
     
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  3. dMEK

    Thread Starter New Member

    Apr 4, 2019
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    This was the circuit I ended up with - it functions as desired - thanks for all the advice

    I had to add R7 so that C2 would drain a bit faster for a better ramp down time


    upload_2019-4-15_13-39-28.png
     
  4. dMEK

    Thread Starter New Member

    Apr 4, 2019
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    Okay - I had to remove R6 to get the timed pulse to operate correctly

    finally I would like the output to only give a signal for the length of the pulse, even if SW1 is held down - 1 pulse per trigger
    Is it possible to do this with only analog components?
     
  5. dMEK

    Thread Starter New Member

    Apr 4, 2019
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    I found this circuit for a differentiating input to generate a short pulse rather than continuous signal from the switch - this should solve the issue?

    [​IMG]
     
  6. dMEK

    Thread Starter New Member

    Apr 4, 2019
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    Well, that did the trick

    Final design then:
     
  7. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    All the parts are in the right places.

    HOWEVER - if RV1 is fully clockwise, U1 will eventually fail. To be clear, that is assuming RV1 is not ultra-cheap. Cheap pots do not go to zero resistance when the wiper is against one of the stops, and that might save your chip. But don't confuse luck with good design.

    ak
     
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  8. dMEK

    Thread Starter New Member

    Apr 4, 2019
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    Hey - yes, saw that - I put the 1k resistor from RV1 to VCC back, it works fine now, thanks
     
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