Electronic Canary


Posted on Feb 5, 2014

This circuit is a modified hartley oscillator with a couple of extra components included. The transformer is a small audio transformer, type LT700. The 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 capa


Electronic Canary
Click here to download the full size of the above Circuit.

citor 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.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Remote controlled LED
    Led bar-graph driver
    Stamp9G20
    Shock alarm circuit
    How to install CCD camera sensor with VHF sender
    Servo Driver



    Top