Have you ever forgotten to shut your home door at night? This might be a terrible experience as it can provide a way to thieves to enter your home. Here is a simple electronic project that alarms or visually indicates whenever the door is left open. This circuit can be used for a variety of purposes like home security, refrigerator door indicator, etc. For sensing the door position different types of methods can be used such as magnetic, light beam, mechanical, electrical, etc
In this project, a reed switch is used which is simply an electrical switch activated by a magnetic field. It looks like a small tube-like device containing two ferrous material leads. Reed switches are available with Normally Open (NO) and Normally Closed (NC) types. In a NO reed switch, the ferrous terminals inside the reed switch remain in an open position when there is no magnetic field. When any magnetic field comes near the reed switch it closes the contacts and creates a conducting path. Whereas, a normally closed switch works just in the opposite way.
Hardware Components
The following components are required to make Door Indicator Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Battery | 9 to 12V | 1 |
| 2. | Relay | 12V | 1 |
| 3. | IC | NE555 timer | 1 |
| 4. | Diode | 1N4007 | 1 |
| 5. | Resistors | 100K | 1 |
| 6. | Reed switches | – | 3 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
Door Indicator Circuit
Working Explanation
This simple door alert circuit can easily be made with a few components. The key components are 555 timer IC and reed switches. The circuit uses three normally closed reed switches, which can be placed on desired doors. The number of reed switches can also be increased depending on the door size. The output of these switches goes to the 555 timer IC. A relay switch is connected at the output of the IC, from which you can connect any AC or DC bulb for visual indication. You can also connect any AC or DC alarm with it for alarm alerts. The operating voltage of the circuit is 9V to 12V DC. It can also be operated the voltages below 9V but it is a must to use the same voltage relay.
Applications and Uses:
The door alarm warns the owner by emitting a loud siren sound or a flashing light, or both if there is unauthorized access to the home or office door. It is also used as a warning alarm if the door of a store or garage is left open by mistake. This circuit can also be used as a refrigerator door indicator, car door indicator, etc.
