The grating circuit is used to detect the presence
of any person or object in a specific area. The detection range of Light
Fence Circuit is approximately 1.5 to 3 meters. Using LDR and
operational amplifier to design the circuit is quite simple. This
portable circuit can be easily operated with a commonly used 9V battery,
and the warning sound generated by the buzzer is loud enough to detect
people, cars or objects.
Hardware Required:
Circuit:
Working:
The circuit can run on a 9-volt battery. The operational amplifier IC is
used as a voltage comparator in the circuit, and the 555 timer IC is
placed in an astable mode. The voltage divider circuit is generated by
the LDR and potentiometer. The output of the frequency divider circuit
can vary according to the amount of light falling on the LDR. The
voltage divider is connected to the inverting board of the operational
amplifier IC. A 5.7K ohm resistor connects the non-inverting pin to the
source and sets the voltage value at the same phase.
To change the voltage as needed, you should replace
the resistor with a 10 K potentiometer. Whenever a person or entity
approaches a prohibited place, the LDR detects the shadow and the
circuit activates an alarm. You can use a potentiometer connected in
series with the LDR to adjust the sensitivity of the device.
