Multi-point monitoring alarm

Multi-point monitoring alarm

This door opening alarm indication circuit can monitor three doors at the same time. If someone breaks in, it will immediately send out an audible and visual alarm.

You only need to install the reed switch unit on the door frame of each monitored door, and install three magnets on the three corresponding doors so that the magnets can align with the reed switches when the doors are closed. In addition to the three identical door monitoring circuit units, there is also an independent common unit, which consists of a power supply, three LEDs and a buzzer, and is placed indoors where you can monitor and handle it. The door monitoring circuit unit and the common unit are connected by a six-core braided cable.

When the gate is closed, the reed switch contacts are attracted by the magnet and closed, and the alarm circuit does not work, indicating that everything is normal. When the gate 1 is opened by someone, transistors T1 and T2 are turned on, the buzzer sounds an alarm, and LED1 lights up, indicating that the gate 1 is opened by someone. Due to the latching effect of diode D1 and transistors T1 and T2, the alarm will not stop even after the gate is closed again. To stop the alarm, press the reset switch S1 to reset the gate monitoring circuit unit 1.

The other two gate monitoring circuit units work in the same way and do not interfere with each other.

In order to prevent AC power failure, a 9V backup battery is provided to ensure uninterrupted power supply. When the three doors are opened at the same time, the three LEDs light up at the same time.