Clap-Counting Fan Speed Controller

The classic clap switch is a one-trick circuit: clap once, the light toggles. This project takes the idea seriously and builds a multi-level controller out of it — counting claps instead of merely detecting them turns one binary input into four commands, enough to run a fan's speed steps hands-free. The engineering is in two places: the acoustic front end, which must catch a clap's sharp transient while ignoring conversation and TV audio, and the power stage, where a triac with zero-cross timing regulates a real AC fan. Together they make a touchless controller that is genuinely usable and a strong demonstration of signal conditioning plus power electronics.

1. The electret microphone picks up room sound; the preamplifier boosts it and the comparator fires a digital pulse on sharp transients.
2. Firmware timestamps each pulse and counts how many arrive inside the 1.5-second clap window, ignoring pulses closer together than the debounce gap.
3. One clap sets speed 1, two claps speed 2, three claps speed 3, four claps switch the fan off.
4. The selected speed maps to a triac firing angle; the zero-cross detector keeps every firing synchronized to the mains cycle.
5. The triac conducts for the chosen fraction of each half-cycle, regulating the fan motor's effective voltage.
6. The speed LEDs update on every valid command, and the manual override switch forces full speed regardless of clap state.

Tech stack:

• Arduino Nano (ATmega328P)
• Electret microphone + preamplifier/comparator
• BT136 triac · MOC3021 optocoupler
• Zero-crossing detector circuit
• 3-LED speed indicator
• 230V AC fan demo load
• Potentiometer sensitivity trim

• [Clap counting, not just detection] Firmware counts 1–4 claps inside a 1.5-second window to select low, medium, high or off — four commands from one microphone.
• [Electret-mic front end] Microphone with preamplifier and comparator converts the clap transient into a clean digital pulse.
• [False-trigger filtering] Amplitude threshold plus minimum-gap timing rejects speech, TV audio and single knocks; the sensitivity is potentiometer-adjustable.
• [Triac fan regulation] Zero-cross synchronized triac phase-cut drives the fan at three real speed steps.
• [Speed indicator LEDs] Three LEDs show the active speed level at a glance.
• [Manual override switch] A physical switch bypasses clap control for users who just want the fan on.
• [Startup calibration] Power-on self-check confirms the mic chain and triac stage before accepting claps.

• Working clap-counting fan controller prototype with demo fan
• Arduino firmware (clap counting, debounce, triac timing, LED indication)
• Full wiring diagram and mic/triac placement documentation
• Sensitivity-tuning and false-trigger test procedure
• Project report PDF (acoustic detection, clap transient analysis, triac fan control, measurements)
• PPT presentation for final review
• Viva Q&A preparation document (electret biasing, comparator thresholding, zero-crossing, motor speed control)

• Loud continuous noise (music, TV at high volume) can mask claps or cause false counts — this is a teaching controller, not a noise-immune industrial input.
• Triac phase-cut fan control can produce an audible motor hum at low speeds on some fans; the report documents this as a known characteristic.
• Detection range of 3–4 m is an expected figure in a quiet room; reflective rooms and background noise reduce it, and the student verifies their own range.
• The 1.5-second window means commands take a beat to register — it is deliberate counting, not instant reaction.
• Only the four defined clap patterns are recognized; there is no voice or pattern learning in the base build.