Automatic Room Light Controller with Bidirectional Visitor Counter using IR Sensors

Classrooms, seminar halls and laboratories burn electricity for hours with nobody inside because the last person out forgot the switch — or because nobody wants the responsibility of turning the lights off. This project removes the human from the loop: two IR transmitter-receiver pairs mounted a few centimetres apart across the doorway detect not just that someone passed, but which direction they were walking. Breaking the outer beam first and then the inner one means entry (count up); the reverse order means exit (count down). An Arduino Nano keeps the running total on a 7-segment display and drives a relay that powers the room light only while the count is above zero. The result is a room that lights itself for its occupants and goes dark the moment it empties — a small, honest piece of energy saving built from parts any electronics lab already stocks.

1. Two IR transmitter-receiver pairs are mounted across the doorway about 10–15 cm apart — an outer pair and an inner pair.
2. When a person enters, they break the outer beam first and the inner beam second; the Arduino reads this A-then-B sequence as an entry and increments the count.
3. When a person leaves, the inner beam breaks first and the outer second (B-then-A); the count decrements, never dropping below zero.
4. The firmware debounces each beam (a break must persist a few milliseconds) and discards sequences that do not complete within a timeout window.
5. The current count is written to the 7-segment display after every change.
6. The relay output follows a simple rule: count greater than zero → light on; count equals zero → light off. The manual override switch bypasses this rule when engaged.

Tech stack:

• Arduino Nano (ATmega328P)
• IR transmitter-receiver sensor pairs × 2
• 7-segment LED display
• 5V relay module (SRD-05VDC-SL-C)
• Push-button (reset) + toggle switch (override)
• 5V regulated power supply
• Buzzer (optional occupancy alert)
• Arduino IDE (C++ firmware)

• [Bidirectional counting] Two IR beam pairs read the break sequence to distinguish entry from exit, so the count tracks real occupancy instead of just motion.
• [Automatic light control] A 5V relay module switches the room light on when the count rises above zero and off when it returns to zero — no switches to remember.
• [Live count display] A 7-segment display shows the current number of people inside, useful for the demo and for the room's own awareness.
• [Debounce and sequence logic] Firmware ignores partial beam breaks and times out incomplete sequences (someone who steps in and backs out), keeping the count stable.
• [Manual override] A toggle switch forces the light on regardless of count for cleaning and maintenance, with an indicator LED showing override state.
• [Reset function] A push-button zeroes the count for resynchronisation, documented as part of the operating procedure.
• [Single 5V supply] The logic side runs from one regulated 5V adapter; the relay contacts are rated for standard 230V room lighting loads.

• Assembled and tested prototype (Arduino Nano, IR pairs, display, relay module, switches)
• Complete firmware source with direction/debounce logic
• Circuit diagram and doorway mounting layout
• Operating and resynchronisation procedure
• Project report PDF (IR sensing, direction logic, relay driving, methodology)
• PPT presentation for final review
• Viva Q&A preparation document (beam sequencing, debouncing, relay isolation, occupancy edge cases)
• Bill of materials with sourcing pointers