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.
Applications and Uses
The door left open indicator alarm is used in Door Security Systems for security purposes.
