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Newbie Needs Help In a Dark Sensor

Discussion in 'Sensors and Actuators' started by Ahsan Jamal, May 30, 2015.

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  1. Ahsan Jamal

    Ahsan Jamal

    1
    0
    May 30, 2015
    Hello Guys I am a begginer in electronics and need a help in my first circuit. i am making a dark sensor and i used
    Transistor BC547
    LED
    LDR
    Resistor 150k ohms
    Buzzer
    Battery
    I Want To Know Whats Problem In This Circuit Which I have Made.
     

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  2. hevans1944

    hevans1944 Hop - AC8NS

    4,474
    2,085
    Jun 21, 2012
    Looks okay in principle, but the 150 kΩ resistor may not provide enough bias to turn the transistor on enough to reliably operate the buzzer. You might consider a Darlington connection using two of the BC547 transistors.
     
  3. Arouse1973

    Arouse1973 Adam

    5,164
    1,080
    Dec 18, 2013
    And also it won't be a quick switch over from off to on as it gets dark. You may find the buzzer starts to sound at low volume as the transistor starts to conduct and get louder and louder until the transistor is fully on. A comparator circuit with hysteresis will normally sort this out.
    Thanks
    Adam
     
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