In this DIY, we are making a “Fridge door alarm circuit using 555 and LDR.” The name “Fridge door alarm circuit” itself deduces the application. This circuit triggers the alert if the “door of the fridge” is left open for a long time. At the point when the door of the cooler is left open, the temperature inside the lodge will expand.
This ascent in temperature will be detected by the indoor regulator and attempt to chill off the lodge. It will consistently attempt to keep up the steady temperature of the framework. The compressor will be working consistently to eliminate the hotness of the lodge; this expands the force utilization from the container. Likewise, consistent use under this condition would decrease the life of the compressor. That’s why we are making this circuit to save your life.
Hardware Component
The following components are required to make the Fridge Door Alarm Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Diode | 1N4007 or 1N4001 | 1 |
| 2. | IC | NE555 timer | 2 |
| 3. | LDR | 5mm | 1 |
| 4. | Electrolytic Capacitor | 47uF | 1 |
| 5. | Ceramic Capacitor | 0.1uF | 1 |
| 6. | Buzzer | – | 1 |
| 7. | Breadboard | – | 1 |
| 8. | Connecting wires | – | – |
| 9. | Resistor | 10KὨ, 150KὨ, 470KὨ, 100 | 1, 1, 2, 1 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
The Fridge Door Alarm Circuit
Working Explanation
A 9 V battery fuels the entire circuit. At the point when the refrigerator door is closed, it is dark and the resistance of the LDR is almost 1 MὨ as given in the datasheet. The potential divider’s yield voltage shows up over the capacitor and it stays in charged condition (Voltage higher than 2/3Vcc), making the output “LOW.” At the point when we open the refrigerator or fridge, the light will also open and LDR which lets down the resistance and makes the capacitor “discharge.”
After this voltage is lower than 2/3Vcc, the yield begins to “oscillate” at a certain “frequency,” and the yield is “HIGH.” Once more, the capacitor charges and arrives at a limit proceeded by the “discharge.” This proceeds until the “LDR resistance” goes “HIGH,” which will occur without light when the door is closed.
Applications and Uses
This fridge door alarm circuit is used to identify if the fridge door is open for a long.
