The Clapper

BRIEF Give the machine ears

In 1985 a gadget called The Clapper sold millions: clap twice and your lamp obeyed. People thought it was magic. It was a microphone, a threshold and a switch, three things you already understand. Today you build it: the kit's sound sensor hears the sharp crack of a clap, and your code flips the lamp. You will also meet a genuinely important idea, state, the machine's memory of where things stand.

Time: 45–60 minutes · Difficulty: 3/5 · You need: Lesson 03 done (the toggle remix helps a lot).

KIT What you need

• R3 board with USB cable
• Breadboard
• The sound sensor module (small board with a round silver microphone and a blue square dial)
• 1 LED and its 220Ω resistor
• Jumper wires

BUILD Wire it

Unplug the USB. Push the module's pins into the breadboard, wire from its rows. The pins are labelled on the board, read YOURS (usually DO, +, G, and sometimes AO which we ignore today).

From	To	Why
Module DO pin	R3 pin 7	The yes/no answer wire
Module + pin	R3 5V	Power
Module G pin	R3 GND	Ground
R3 pin 13	220Ω resistor → LED long leg	The lamp
LED short leg	R3 GND	Loop complete

CODE Program it

// GAMERIFT Beginner Kit, Lesson 10: The Clapper
// A clap toggles the lamp. State + cooldown do the real work.

const int soundPin = 7;
const int lampPin  = 13;

bool lampOn = false;          // the machine's memory

void setup() {
  pinMode(soundPin, INPUT);
  pinMode(lampPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  if (digitalRead(soundPin) == HIGH) {   // the sensor heard something sharp
    lampOn = !lampOn;                      // flip the memory
    digitalWrite(lampPin, lampOn);         // make the lamp match it
    Serial.println(lampOn ? "CLAP! Lamp on" : "CLAP! Lamp off");
    delay(400);                            // cooldown: one clap = one flip
  }
}

Now tune it, this is the important part:

1. Upload, open the Serial Monitor, and clap about a metre away. Nothing? The dial is set too strict.
2. Give the blue dial a small turn with the little screwdriver (or ask an adult for one), then clap again. Repeat until a clap triggers it but talking does not.
3. Some modules answer LOW instead of HIGH when they hear a spike. If your lamp toggles constantly and ignores claps, change == HIGH to == LOW. Reading the sensor's dialect is real engineering.

BREAK IT Now break it on purpose

1. Turn the dial to maximum sensitivity. The lamp now flips when you speak, type, or exist. An over-sensitive sensor is as useless as a deaf one, calibration is a compromise, always.
2. Remove the delay(400) and clap once. The lamp flickers through several flips and lands randomly. That is the "one clap is many bangs" problem, live. Put the cooldown back.
3. Try triggering it without clapping: keys jangling? A whistle? A knock on the desk? You are mapping what "sharp sound" means to this microphone.

REMIX Make it yours

• The double-clap: the real 1985 Clapper needed clap-clap to avoid false triggers. Require two claps within one second. Hint: remember the time of the first clap with millis(), look it up, it is a timestamp in milliseconds.
• Clap counter: put Lesson 07's display back on and show how many claps it has heard. Applause meter for family debates.
• Snap orchestra: clap toggles the lamp AND plays a note from Lesson 08. Different trigger sounds, different notes, if you can tune it that finely, you have out-engineered this lesson.

LOG IT Show and tell

Film the clap-on, clap-off moment for your lesson log, it is the most demo-able build in the course. Stuck? Contact us with a photo and tell us what the Serial Monitor says.