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:

New Circuits

.

 


Popular Circuits

LED display Digital Calendar AT89C2051
8 way Up/Down Switcher
Toggle on off switch
Security / Automation Sensors using Arduino
12V voltage doubler circuit
12vdc 220vac inverter
Detector switch circuits
Solar Cell Voltage Regulator
IR Short Distance Beam Cut Detector
ZL1BPU exciter



Top