Circuit Diagram of Automatic Door Bell Using Object Detection: Automatic Door Bell With Object Detection Circuit
Circuit Diagram of Automatic Door Bell Using Object Detection:
This circuit operates using a pair of ultrasonic transmitter and receiver
modules which are used to detect the person and then if the person is
detected, the door bell is automatically turned ON when the person is
in-front of the door.
The ultrasonic transmitter operates at a frequency of about 40 Kilo-Hertz. That means it continuously transmits the ultrasonic waves of about 40KHz. The power supply
should be moderate such that the range of the transmitter is only about
one or two meters. If the transmitting power is less than one meter,
then there is a chance that the person who is one meter away is not
detected. Also, if the range is set to be very large, then it may lead
to false triggering, meaning that, the objects far away from our door
are considered as the visitors and the alarm rings. This can be a
nuisance for us if the alarm rings for every object or person far away.
So, to avoid both the problems, the transmitting power is kept to an
optimum level.
The ultrasonic receiver module receives
the power at the frequency same as that of the transmitter’s so that
noise will be eliminated and we get less false triggering. The
sensitivity of the receiver can be tuned by using the 500K-ohm variable resistor
arranged as a pot in the circuit. By tuning this properly, we can
achieve the desired results. The output of our circuit is given to a
buzzer circuit which acts as a doorbell in our case. The receiver in
this circuit uses IC LM324 which is internally has four op-amps. Out of
the four op-amps, we are using only four of them and leaving the other
one unused as it is not much required in our case. The three op-amps are
used in cascaded arrangement to provide high gain as well as noise free
output.
An opto coupler is used at the output to avoid any interaction between our circuit and the door bell.
Assemble the circuit on a PCB as compactly as possible and then attach it to your main door.
Thats it! You may provide a power supply using a 9V DC adapter with
filtered and regulated output. If the 9V adapter with regulated output
is not available, then we recommend you to use a 12V unregulated DC
adapter with 7809 voltage regulator.
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