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Building a Carbon Monoxide Detector
Ed

Imeundwa na

Ed

13. Julai 2026FI
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Building a Carbon Monoxide Detector

Build a circuit that senses carbon monoxide (CO) — the invisible, odourless gas from any incomplete combustion — and raises an alarm when it rises. An MQ-7 sensor gives the Arduino a reading that climbs with CO; the code compares it to a clean-air baseline and triggers a buzzer and red LED. A great way to learn gas sensing — but read the safety note: this is a demonstration, NOT a certified life-safety CO alarm.

Kati
1-2 hours

Maagizo

1

Wire the sensor, buzzer and LED

On the breadboard: MQ-7 VCC to Arduino 5V, GND to GND, and its analog output (AOUT) to Arduino A0. Active buzzer + to pin 8, - to GND. Red LED anode to pin 7 through a 330 Ω resistor, cathode to GND.

Vifaa kwa hatua hii:

Arduino Uno R3Arduino Uno R31 kipande
Carbon Monoxide Sensor - MQ-7Carbon Monoxide Sensor - MQ-71 kipande
Active Buzzer Module (5V, 5-Pack)Active Buzzer Module (5V, 5-Pack)1 kipande
LED - Basic 5mmLED - Basic 5mm1 kipande
Resistor 330 Ohm 1/6 Watt PTH - 20 packResistor 330 Ohm 1/6 Watt PTH - 20 pack1 kipande
BreadboardBreadboard1 kipande
Jumper Wires (Male-to-Male)Jumper Wires (Male-to-Male)1 paketi
2

Connect and open the IDE

Plug the Arduino into your computer with the USB cable, open the Arduino IDE, and select Arduino Uno and its serial port.

Vifaa kwa hatua hii:

USB-B CableUSB-B Cable1 kipande

Zana zinazohitajika:

Computer with Arduino IDEComputer with Arduino IDE
3

Upload the detector sketch

Paste this sketch and upload. It warms the sensor for two minutes, records a clean-air baseline, then sounds the buzzer and lights the LED whenever the reading climbs above that baseline.

co_detector.inoarduino
// Carbon monoxide INDICATOR using an MQ-7 sensor.
// NOT a certified life-safety alarm - see the blueprint's safety note.
// MQ-7 analog output on A0; buzzer on pin 8; red warning LED on pin 7.

const int MQ7_PIN = A0;
const int BUZZER_PIN = 8;
const int LED_PIN = 7;

int cleanAirValue = 0;          // baseline, measured at startup
const int ALARM_MARGIN = 150;   // how far above baseline triggers the alarm

void setup() {
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(LED_PIN, OUTPUT);
  Serial.begin(9600);

  Serial.println("Warming up the MQ-7 (2 min) in clean air...");
  delay(120000);                // 2-minute warm-up
  cleanAirValue = analogRead(MQ7_PIN);
  Serial.print("Clean-air baseline: ");
  Serial.println(cleanAirValue);
}

void loop() {
  int reading = analogRead(MQ7_PIN);
  Serial.println(reading);

  if (reading > cleanAirValue + ALARM_MARGIN) {
    digitalWrite(LED_PIN, HIGH);      // CO above baseline -> alarm
    digitalWrite(BUZZER_PIN, HIGH);
  } else {
    digitalWrite(LED_PIN, LOW);
    digitalWrite(BUZZER_PIN, LOW);
  }
  delay(500);
}
4

Warm up, baseline and test

Power it in fresh air and let the 2-minute warm-up set the clean-air baseline (a brand-new MQ-7 also needs a longer 24–48 h burn-in before its readings settle). Then hold a small CO source nearby in a ventilated room — the smoke from a just-blown-out match works — and the buzzer and LED should trigger. Change ALARM_MARGIN to make it more or less sensitive.

5

Important safety limits

This is a LEARNING project and, at best, a supplementary indicator — it is NOT a certified life-safety device. A hobby MQ-7 gives a relative reading, not a calibrated ppm; it drifts over time and needs regular re-baselining, and it also responds to smoke and other gases. Carbon monoxide is invisible, odourless and can be fatal: for real protection always use a UL- or EN-certified CO alarm. Never rely on this circuit to keep anyone safe.

Vifaa

8

Zana Zinazohitajika

1
Jumla inayokadiriwa
$58.00

Blueprint zinazohusiana

Blueprint hizi zinashiriki maarifa — mbinu, vifaa au kanuni

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CC0 Umma Wote

Mchoro huu umetolewa chini ya CC0. Uko huru kunakili, kubadilisha, kusambaza, na kutumia kazi hii kwa madhumuni yoyote, bila kuomba ruhusa.

Saidia Mtengenezaji kwa kununua bidhaa kupitia Mchoro wao ambapo wanapata Kamisheni ya Mtengenezaji iliyowekwa na Wachuuzi, au unda marudio mapya ya Mchoro huu na uiunganishe kama kiungo katika Mchoro wako kuchangia mapato.

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