Door Knock Alarm With Timer
₹499 – ₹949
- Product Code: LGKT044
- Power supply: No battery included, Includes DC adapter if required with the kit
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Shipping DetailsUsually delivered in 2-3 days International Shipping Not Available
This low-cost circuit uses the piezoelectric element of a piezobuzzer as the input sensor. The piezoelectric element plate is fixed at the centre of the door wing by using a cello tape. Apply a small quantity of adhesive at the edges between the plate and the door. Extend wires about 1-1.5 metres from the piezoelectric to the circuit. IC NE555 is configured in monostable mode.
When it gets an input pulse its output goes high for a period set by Variable resistor, resistor and capacitor. IC UM66 is used as a melody generator. When the door is knocked at, the piezo plate generates an input pulse, which is amplified by transistor. The amplified signal triggers the timer IC NE555 and its output pin 3 goes high to enable the melody generator. Music is heard from the speaker. After the set time period, the melody sound stops.
- Dimensions (cm) LxWxH: 18 x 15 X 7
- Weight (kg): 0.5