uln2004-water-level-indicator

Discussion in 'The Projects Forum' started by BBQ, Aug 10, 2014.

  1. BBQ

    Thread Starter New Member

    Jan 22, 2014
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    Hi there I'm looking for some help...I built the circuit and working fine however what I would like to do is once led 2 is no longer illuminated the water has drained below P2 to activate the buzzer from that point.

    Cheers
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,388
    1,605
    Another inverter connected to pin 11 to will drive a buzzer connected to +V.
     
  3. BBQ

    Thread Starter New Member

    Jan 22, 2014
    23
    0
    Any idea for the inverter components to implement with this ?.

    Cheers
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,986
    745
    Just connect the buzzer + to pin 11 and ground, so that when the led goes out the buzzer sounds.
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,800
    1,103
    Could you abandon P1 and use inverter 7 in a new role to operate the buzzer?
     
  6. BBQ

    Thread Starter New Member

    Jan 22, 2014
    23
    0
    Alec T that was my first consideration but the way I have it laid out on the board I will use all the inputs for this application....at point 2 is where I need the buzzer to activate at a later date I may change that though.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,547
    2,371
    Use a ULN2805 has 8 gates, take the output of P2 to the spare inverter and the output to the buzzer P7.
    Max.
     
  8. BBQ

    Thread Starter New Member

    Jan 22, 2014
    23
    0
    MaxHeadRoom yes that's the IC I should have used but it's made up now and I bought 20 on fleabay so I'm sort of in a jam lol...cheers
     
  9. BBQ

    Thread Starter New Member

    Jan 22, 2014
    23
    0
    Dodgydave when the led is on so is the buzzer.
     
  10. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    You can try the circuit as below, I'm not sure about the current of Buz, if the current less then 33mA then you can using 2N3904, if the current more then 33mA, then you should pick up the bjt for some more current.

    [​IMG]
     
    Last edited: Sep 12, 2014
    BBQ likes this.
  11. BBQ

    Thread Starter New Member

    Jan 22, 2014
    23
    0
    ScottWang Thats exactly what I was thinking of but not the experience to solve....and this will work when the LED 2 turns off....Thank you very much appreciated....cheers
     
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