Wednesday, March 20, 2013

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Bird Sound Generator circuit

This generate a sound like bird’s circuit. The trafo LT700 is a small audio transformer with primary is center tapped with an impedance of 1Kohms at 1KHz . The secondary has an impedance of 8 ohms.

The inclusion of R1 and C1 give this oscillator its characteristic “chirp”. As the 100u capacitor charges via the 4.7K resistor, R1 the bias for the transistor is cut off. This causes the oscillation to stop, the capacitor discharges through the base emitter circuit of the transistor and oscillations start again. Altering these components alters the frequency of the chirp. The chirp is also voltage dependent. When the push button switch is operated the 100u capacitor is charged. When its released, the oscillation decays and the chirp becomes faster.


Transistor BC177 description

NPN transistor in a TO-18; SOT18 metal package. PNP complement: BC177.
Data reverence Transistor BC177

    VCBO/ collector-base voltage open emitter: 30 V
    VCEO/ collector-emitter voltage open base: 20 V
    VEBO/ emitter-base voltage: 5 V
    ICM/ peak collector current - 200 mA
    Ptot/ total power dissipation Tamb £ 25 °C - 300 mW
    hFE DC current gain IC = 2 mA; VCE = 5 V: min 200 max 800
    fT transition frequency IC = 10 mA; VCE = 5 V; f = 100 MHz: min 100 MHz
    Tstg/ storage temperature: Min -65 max +150 °C
    Tj/ junction temperature max 175 °C
    Tamb/ operating ambient temperature min -65 max +150 °C




LT700 Tranformer is a small audio transformer with primary is center tapped with an impedance of 1Kohms at 1KHz . The secondary has an impedance of 8 ohms.

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