Door open alarm using 555 timer circuit
This door open alarm electronic project is designed using an linear hall effect device and a 555 timer circuit. This door open alarm alarm electronic project is based on the TL3103 linear hall effect device used for detecting the angle of rotation. The TL3103s are centered in the gap of a U-shaped permanent magnet.
This type of circuit can sense the opening of a refrigerator door. When the door opens, a triac could be activated to control the inside light.
When the door is opened, an LED turns on and the piezo alarm sounds for approximately 5 seconds.
When the door is in the closed position, the TL3019 output goes to logic low, and remains low until the door is opened.
Usually a 555 timer circuit is triggered by taking the trigger, pin 2, low which produces a high at the output, pin 3. In this configuration with the door in the closed position, the TL3019 output is held low. The trigger, pin 2, is connected to Vi the supply voltage Vcc .When the door opens, a positive high pulse is applied to control pin 5 through a 0.1 uF capacitor and also to reset pin 4. This starts the timing cycle. Both the piezo alarm and the LED visual indicator are activated.
This door alarm electronic circuit project must be powered from a 5 volt DC power supply .