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    In many cases, a doorbell that sounds off a musical tone is preferable over the common buzz sound. This featured circuit is a musical doorbell. After the button S1 is pressed, a short melody is played. When the button is pressed many times in rapid succession or pressed longer, a different melody is generated and the melody plays longer.

    The circuit works this way: when the button S1 is activated the inputs of U3 and one input of U1 switches to logic “0″. The data input (pin 7 of IC 4015) becomes logic “1″. The 4015 is a static 4-bit shift register. Each clock impulse coming from U4 shifts this logic “1″ further in the register. The clock frequency is around 5 Hz.

    The number of shifted logic “1″ is directly dependent on the length of time the switch S1 is closed. Once at least one shift register is logic “1″, a current flows to the base of T1 through a corresponding resistor. The transistor T1 functions as a current controlled oscillator. The tone pitch is dependent on the logic state of the different flip-flop outputs of the shift register. Each clock pulse shifts the logic “1″ in the register. One output of the register (pin 2) is coupled back to U2 and U3 so that all the logic “1″ in the register always run in a loop.

    Schematic of the musical doorbell circuit

    musical doorbell circuit schematic

    When S1 is released (opened), the register runs until the capacitor C1 gets discharged through R2. When S1 is again pressed (closed), the capacitor C1 stays charged causing the musical bell to play continously.

    The difference between two ways of activating the switch S1 is that different combinations of logic “1″ are inputted into the shift register. These different combinations produce the different melodies plyed by the circuit. The musical doorbell must be connected to an audio amplifier. The supply voltage is not critical. It can be between 5 and 15 volts. The circuit consumes around 15mA.

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    10 Responses to "Musical Doorbell Circuit"

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    1. it is good but i need more all details about this . bcause i have to do a project on musical door bell.

    2. this circuit is best.

    3. reynel cm says: on February 8, 2010 at 11:14 pm

      nice circuit. I’ve tried this circuit, but doesn’t work for me. is the 2sc732 critical? replacements?. I amplified this with an LM386, but no sound. thanx

    4. it is good but i need more all details about this . bcause i have to do a project on musical door bell.

      nice circuit. I’ve tried this circuit, but doesn’t work for me. is the 2sc732 critical? replacements?. I amplified this with an LM386, but no sound. thanx

    5. charles wafula says: on March 7, 2011 at 9:09 am

      thanks for the projects keep them coming

    6. Dear sir,
      Did this circuit works properly… is there any problem occur or not… we have plan to do this doorbell as mini project

    7. sir whats the full form of U1,U2,U3,U4… pls say me about this full form

      • U1 to U2 is IC 4093 i.e. QUAD 2-input NAND Gate with schmitt trigger option. You might have studied it in Digital Design.
        Also “U” is an abbreviation used for IC’s.

    8. dear sir,

      did the circuit is work properly, plz reply me sir.

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