Door Left Open Indicator Alarm using Reed Switch

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In this project, we will discuss the “Door Left Open Indicator Alarm Circuit”. A door alarm is a miniature electronic device that is connected to the door and used to identify whether the door is “open”. At the point when that door is opened, an alert is activated. So, this basic project can be used to make a door security framework. It will alert if the door is left open.

The circuit will demonstrate by actuating an alarm associated with the output of the 555 timer IC, and when the door is closed it will switch off automatically. The necessary timeframe can be chosen by changing the estimations of the capacitor Cx. The maximum chosen time can be any from 5 minutes to 15 minutes or more.

Hardware Components

The following components are required to make Door Indicator Alarm Circuit

S.no	Component	Value	Qty
1.	Reed Switch	–	1
2.	Transistor	2N4401, BC327, S8550	1, 1, 1
3.	IC	NE555 timer	1
4.	Diode	1N4148	1
5.	Resistor	1K, 1M, 4.7K, 220Ω	2, 1, 1, 1
6.	Ceramic Capacitor	0.1µF	2
7.	Electrolyte Capacitor	47µF, 0.1µF	1, 1
8.	IC	UM66	1
9.	Speaker	8Ω	1
10.	LED	–	1
11.	DC Supply	4.5V	1

NE555 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer

UM66 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of UM66

Door Indicator Alarm Circuit

Working Explanation

Now we will talk about the circuit of the “Door Left Open Indicator Alarm”. A sensor is used in this circuit which is an “open reed switch” that can be set with the circuit at the edge of the door. A reed switch additionally requires a permanent magnet that ought to be set on the door before the reed switch. The working voltage of the circuit is 4.5V DC. For working with 3V supplant the 555 timer IC to its lower voltage rendition 7555. The circuit won’t utilize any power in the resulting mode because of which the batteries will keep going for years.