In this tutorial, we are making a project on a Fridge door alarm. In order to save the food stored in the fridge from spoiling and maintain its freshness, it is necessary to close the door of your fridge properly. If a fridge’s door is not closed properly then I will cause a load on the compressor to maintain the cooling and it will use more electricity as compared to a completely closed door. These issues can be solved with this circuit as it will produce an alarm when the door of the fridge is left open for a long time.
This circuit works according to the internet light of the fridge when the door is closed the lamp inside the fridge goes off but if it isn’t closed properly then the lamp remains on. So an LDR will detect the light of this lamp and activates the timer circuit.
Hardware Components
The following components are required to make Fridge Door Alarm Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Input Supply DC | 6-9V | 1 |
| 2. | LDR | – | 1 |
| 3. | Transistor | 2N2222 | 1 |
| 4. | Resistor | 100KΩ, 10KΩ | 1, 1, 1 |
| 5. | Capacitor | 10µF, 0.1µF | 1, 1 |
| 6. | IC | NE555 Timer | 1 |
| 7. | Buzzer | – | 1 |
| 8. | Variable Resistor | 1MΩ | 1 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
Fridge Door Alarm Circuit
Working Explanation
The operating voltage of this circuit is 6 to 9 volts DC. There are two sections in his circuit. In the first section, there is a light sensor circuit built around a 2N222 transistor and the second section is a time delay circuit using a 555 timer IC. The working of this circuit is simple, when the LDR receives the light of the fridge’s lamp it activates the circuit and after a specific time period the buzzer will switch on. This time period is preset which can be adjusted with the 1M variable resistor.
Applications and Uses
Other than a Fridge door alarm this can be used as,
- Light sensing alarms
- Door alarms
- Morning alarms
