is a LM567 chip, LM567 is a versatile tone decoder chip the internal circuitry is designed to detect a specific input frequency from 1Hz to 500kHz, to set the IC for detecting a desired frequency we have to set the center frequency of the IC on the required frequency, this can be done by only three external components, once the center frequency is selected it will become lock and extremely stable. The chip also contains a special internal circuitry for the rejection of out band signals and noise which makes it highly stable and ensures that it will never produce a false output.
This project is designed to detect an IR signal produced by the IC`s own pin 5. The IR transmitter LED sends IR signals which bounce back to the IR receiver when an obstacle is near. The received signals are fed to the input pin 3 of the IC and after receiving the center frequency matched signal the output of the IC (at pin 8) gets low or logic zero which turn on the BC327 transistor and the LED becomes activated.
The proximity & obstacle sensor / detector circuit shown here can be used for several proximity detection purposes, for example it can be used in robotic projects to sense walls and obstacles, contact less switches, electronic hand free faucets etc. The main component of the circuit
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