Clap Switch using Sound Sensor and Arduino

Clap Switch using Sound Sensor and Arduino is a hands-free switching prototype that turns a lamp on or off when a person claps twice. A sound sensor module listens for sharp sounds, an Arduino Uno judges whether the sounds form the expected double-clap pattern, and a relay module switches the lamp circuit in response. The build is deliberately small: one controller, one sensor, one relay and one lamp, so every stage from sound to switching can be traced on a single board. It suits rooms where reaching a wall switch is awkward, such as beside a bed or a workbench, and it demonstrates the core embedded ideas of sensing, threshold comparison, timing logic and electrically isolated switching. Because the lamp is switched through a relay, the low-voltage control side stays separate from the mains side, which is itself an important design lesson for any student working with mains-powered loads.

Many everyday switches assume the user can always reach them, which is not true in the dark, from bed, or with hands full. Voice assistants solve this with a network connection and a microphone that is always listening, but that is a heavy answer for a single lamp. A clap switch is the minimal version of the same idea: a sharp, deliberate sound becomes the command, no network is needed, and the whole decision chain fits on one microcontroller. The engineering interest is not the clap itself but the judgement around it — telling a real double clap apart from a dropped book, a door slam or normal conversation — which is where threshold tuning and timing windows come in.

Clap Switch using Sound Sensor and Arduino works as a short chain from sound to switching: sound reaches the sensor, the sensor turns it into a signal, the Arduino judges the pattern, and the relay acts. A clap strikes the sensor module's electret microphone, which converts the sharp sound into a small electrical signal; the module's comparator compares that signal with the potentiometer-set threshold and outputs a digital pulse for every sound loud enough to cross it. The Arduino watches for these pulses and counts them: a first pulse starts a short detection window, and only if a second pulse arrives inside that window does the firmware treat the pair as a command. It then flips the relay, the relay contacts close or open, and the lamp turns on or off accordingly, while a brief blanking interval stops the relay's own click from being counted as another clap.

1. The sound sensor module's electret microphone picks up room sound and converts it into an electrical signal.
2. The module's LM393 comparator compares the signal with the threshold set by the onboard potentiometer and outputs a digital pulse for each sound above that threshold.
3. The Arduino reads the digital pulse on a digital input pin and timestamps it.
4. The first accepted pulse starts the detection window (design target: approximately 1.5 s); a second pulse inside the window is treated as a double clap, while a lone pulse is discarded when the window expires.
5. On a confirmed double clap, the firmware flips the relay output pin, toggling the relay module and the lamp state.
6. After toggling, the firmware blanks sensor input for a short interval (design target: approximately 0.5 s) so the mechanical click of the relay is not counted as a new clap, then resumes listening.

Builder note from the build: the tuning step that makes the difference is setting the threshold in the actual room, not on the bench alone. Turn the sensitivity potentiometer until the module's onboard indicator just stops flickering in a quiet room, then clap once and check that the indicator flashes once per clap; if ordinary speech triggers it, back the potentiometer off a quarter-turn and test again. The second practical lesson is placement: keep the sensor module away from the relay itself, because the relay's click is loud enough at close range to retrigger an untuned build.

Tech stack:

• Arduino Uno (ATmega328P)
• LM393 sound sensor module
• Single-channel 5 V relay module
• Arduino IDE (C/C++ firmware)
• Breadboard · jumper wires · push button
• 230 V AC demonstration lamp with enclosed holder
• 5 V USB power supply
• Solderless prototype base board

Clap Switch using Sound Sensor and Arduino gives a student four capabilities to demonstrate: double-clap toggle control, adjustable sound sensitivity, false-trigger filtering, and relay-isolated lamp switching. The double-clap toggle is the headline behaviour — two claps switch the lamp, and two more switch it back — while adjustable sensitivity lets the same build be tuned for a quiet bedroom or a noisier living room. False-trigger filtering is what makes the switch usable rather than a novelty: the firmware only accepts claps that arrive as a pair inside a short window, and it ignores the relay's own click after switching. Relay isolation keeps the 5 V control circuit electrically separate from the lamp circuit, and a status LED plus a manual push-button override complete a build that is practical to demonstrate and easy to explain.

• [Double-clap toggle control] [Implemented] Two claps within the detection window toggle the lamp state; two more claps toggle it back. The lamp holds its state between commands, so no continuous sound is needed.
• [Adjustable sound sensitivity] [Implemented] The sensor module's onboard potentiometer sets the sound level that counts as a clap, so the build can be tuned for a quiet room or a noisier space without changing code.
• [False-trigger filtering] [Implemented] The firmware accepts only a pair of sharp pulses inside the detection window and blanks out input briefly after each relay toggle, so the relay's own click cannot retrigger the switch.
• [Relay-isolated lamp switching] [Implemented] A single-channel relay module switches the lamp circuit while keeping the 5 V Arduino side electrically separate from the lamp side.
• [Status LED indication] [Implemented] An LED on the board shows the current lamp state and flashes on each accepted clap, so the audience can follow the decision even when the lamp is out of view.
• [Manual push-button override] [Implemented] A push button toggles the lamp directly, giving a fallback if the room is too noisy for clap control and a simple way to test the relay on its own.
• [Configurable clap pattern and window] [Configurable] The required clap count and the detection window are constants in the firmware, so a student can change the build to a single-clap or triple-clap command and document the trade-off.

• Working clap-switch prototype (Arduino, sound sensor module, relay module, lamp and base board)
• Arduino firmware source code with commented threshold, window and blanking constants
• Wiring diagram and component list
• Threshold-tuning procedure for the student's own room
• Project report PDF (background, sensor and relay theory, methodology, testing procedure)
• PPT presentation for final review
• Viva Q&A preparation document (comparator thresholds, timing logic, relay isolation, mains safety)
• Demonstration guidance for the viva table

Timeline

• Week 1: Component assembly, wiring and first power-on checks.
• Week 2: Firmware, threshold tuning and double-clap logic testing in the demo room.
• Week 3: Final assembly on the base board, report and PPT preparation.
• Week 4: Delivery with demonstration guidance and viva Q&A walkthrough.

Support

• Setup guidance for wiring the prototype and tuning the threshold in the student's room.
• Explanation support for the report, PPT and viva Q&A before the final review.
• Guidance on safe handling of the mains-side lamp wiring during demonstrations.