The door opening alarm circuit or front office visitor alert is used for alerting you when a customer is at your office shop.
Automatic door alarm circuit.
S1 and s2 are the two switches that are used in the circuit so that both can be put in two different places i e.
When the door is closed the magnet is close to the sensor.
And the alarm remains on as long as the door is kept open.
It will produce a beep sound when each new customer or visitor is entering and will automatically switch off after few seconds.
Door open alarm circuit.
For sensing the door position different types of methods can be used such as magnetic light beam mechanical electrical etc.
Pull pin security alarm circuit.
A door opening alarm circuit is an indicator or a security alert device which activates while opening the device attached door.
Presence of north polarity magnetic field generates a low voltage at the output of the sensor.
Ne555 is wired as an astable multivibrator whose reset pin 4 is controlled by the sensor output.
We will use a knife switch in conjunction with a 10kω resistor the 2 of these components form a voltage divider circuit.
As a result pin 4 of ne555 also goes low and the timer does.
Working of security alarm circuit.
The 9 volts that are supplied to this circuit are in parallel with the 10kω resistor and the knife switch with the gate of the scr being.
The schematic for the door alarm circuit is shown below.