In this circuit the TSOP4830 is used as a sensitive infrared detector that does not require shielding from room lighting. The detector will work under almost any lighting condition from complete darkness to full sunlight.
Basic Circuit Operation
The upper portion of the circuit uses two astable 556 oscillators, IC 1A and IC 1B to drive an infrared LED. IC 1A operates at approximately 3Hz with a duty cycle of about 9 percent. IC 1B is adjusted to 30 kHz (the design operating frequency of the TSOP4830) with a duty cycle of about 52 percent.
The 556 – LED driver circuit produces an approximately 10 millisecond burst of 30 kHz light 3 times per second via the infrared LED.
The lower portion of the circuit is the IR detector, time delay and output section. The output of the voltage comparator, IC 3, produces a steady LOW – open collector output when infrared light of the correct frequency is detected by the TSP4830 receiver IC.
When the IR Receiver Module receives a sufficiently strong 30 kHz infrared pulse from D1, its output, pin 3, will go LOW for the duration of the pulse. (About 9 milliseconds.)
When the output of the IR detector goes LOW, the voltage at the PLUS input of comparator, IC 3, will be made LOW and the comparator’s output will go LOW. As long as the infrared pulses are seen by the receiver module the output of the comparator will remain LOW.
The 4.7uF capacitor provides a time delayed resetting of the comparatorso that the output of the comparator is steady between the IR pulses.
When the 30kHz infrared signal is no longer detected, the 4.7uF capacitor will recharge and the output of the comparator will go HIGH.
In typical circuits the output of the comparator would control a LED or drive a relay.
Depending on the circuitboard for the infrared proximity detector circuit, the lower portion of the basic circuit is repeated 4 or 8 times.
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