This shown circuit alarm updates you after some time at any time your refrigerator door is left open.
This circuit turns into easy to carry, simply because in the event the door is left as a result of carelessness might cause tremendous increase in the consumption and influence the lifespan of the fridge.
This circuit utilizes a photosensor LDR for detecting whether the door is open, or not. At any time the sensor is lit up by the light being deducted from within the refrigerator, the circuit starts giving off an irregular sound to warn you and provide the circumstance to your thoughts.
And the moment the door is closed, and the fridge light goes off, the circuit and the alarm shuts off and prevents giving off the sound.
For performing the whole procedure a few timers ICs 555 are associated as displayed in Figure.
When the LDR is not presented to light the voltage on pin 2 (trigger) of the first IC 555 remains higher and its output (pin 3) is presented low. Because of this the second IC 555 is provided inhibited (low voltage level on pin 4) and the alarm is not permitted to switch on.
When the LDR encounters an illumination (door is opened), the voltage level on pin 2 of the first 555 gets low leading to the output (pin 3) to oscillate (square wave).
Throughout the oscillation when output of the first 555 is at high level allows the second 555 to get activated which also starts oscillating in tune with the first but at a more significant frequency.
A buzzer which might be observed associated with the output of IC2 now starts buzzing and alarming.
The circuit utilizes a PP3 9 volt battery, and ought to be located as close as it can be to the inner light of the refrigerator.
The circuit ought to be stored inside a box that could be waterproof and sealed to avoid moisture from influencing its performance.
Refrigerator Door Open Alarm Circuit
Parts list of the refrigerator door open alarm circuit
IC1 - IC2: 2 Timer 555
C1: 1uf 25V
R1: 10K 1 / 4W
R2: LDR (photoresistor)
R3: 2.2M 1 / 4W
R4: 1M 1 / 4W
Buzzer: Piezo type DC