Barking Dog Alarm Circuit
working of Barking Dog Alarm circuit schematic with explanation
Condenser microphone (the alarm)
mounted in the dog’s cage will perceive the sound bark and produces an
AC signal, which pass through the DC blocking capacitor C1 to the base
of transistor BC549 (T1).
Transistor T1 with T2 will strengthen the voice signal and provide
current pulses from the collector of T2. Trigger input pulses applied
to the collector of transistor T3 and combined with capacitor C3 to the
base of the transistor T4, which causes the T4 Cutt-off. The collector
voltage of transistor T4 forward biases transistor T3 through resistor
R8.
Transistor
T1 conducts and capacitor C3 discharges to keep transistor T4 cut-off.
Transistor T4 remains cut-off until capacitor C3 charges enough to
enable it to conduct. When transistor T4 conducts, its collector voltage
goes low to drive transistor T3 into cut-off state. Resistor R9 and
capacitor C3 are timing components. When fully charged, capacitor C3
takes about two minutes to discharge. So when sound is produced in
front of the condenser mic, TRiAC1 (BT136) fires and the bulb (B1)
glows for about two minutes.
