Municipal Sewer Gas Toxic Overload Detector H2s

This a simple setup that can be built using a microcontroller, sensor and a display. For my version I have used:

This Arduino code allows the Arduino to receive data from MCQ136 at one second intervals and display it on the OLED.

The H2S Sensor (SEN0568) by DFRobot is a high-performance device designed to detect the presence of hydrogen sulfide (H2S) gas in the environment. Hydrogen sulfide is a toxic and flammable gas commonly found in industrial settings, making this sensor an essential tool for safety monitoring and environmental analysis. The sensor provides reliable and accurate measurements, ensuring timely detection of H2S gas to prevent hazardous situations.

This circuit is designed for environmental monitoring, specifically for detecting harmful algal blooms (HABs) by measuring pH, turbidity, and temperature. It uses an Arduino Nano interfaced with a pH meter, turbidity module, and DS18B20 temperature sensor to collect data, and a SIM900A GSM module to send SMS alerts when the readings exceed predefined thresholds. The circuit also includes an LCD screen for displaying the measurements and a resistor for the temperature sensor setup.

This circuit is designed for environmental monitoring, utilizing an ESP32 microcontroller to collect data from various sensors including an MQ-136 for H2S detection, an SCD30 for CO2 and humidity measurement, and an SJH-100A for methane detection. The collected data is processed and can be integrated with Home Assistant for real-time monitoring and analysis.

This circuit is a multi-sensor environmental monitoring system using an Arduino Mega 2560. It measures temperature, methane, CO2, pH, and TDS levels, displaying the data on an LCD and controlling a relay based on temperature thresholds. The system also includes Bluetooth communication for data transmission.

This circuit is designed to measure pH and TDS (Total Dissolved Solids) levels in a solution using a pH sensor and a TDS sensor, respectively, interfaced with an Arduino Leonardo. The measured data is then displayed on a 0.96" OLED screen.

The following table outlines the key technical details of the H2S Sensor (SEN0568):

The H2S Sensor (SEN0568) has a simple pinout for easy integration into circuits. The pin configuration is as follows:

Below is an example code to interface the H2S Sensor (SEN0568) with an Arduino UNO:

Q1: Can the sensor detect gases other than H2S? A1: No, the sensor is specifically designed to detect hydrogen sulfide (H2S) gas and may not provide accurate readings for other gases.

Q2: How often should the sensor be calibrated? A2: The sensor should be calibrated periodically, depending on the application and environmental conditions. Refer to the manufacturer's guidelines for calibration intervals.

Q3: Can the sensor be used outdoors? A3: Yes, but ensure it is protected from direct exposure to rain, extreme humidity, and dust to maintain accuracy and longevity.

Q4: What is the lifespan of the sensor? A4: The sensor's lifespan depends on usage and environmental conditions. Under normal conditions, it can last several years with proper care and maintenance.

This project is a safety system I developed to detect harmful gases in sewer pits and alert sanitation workers using voice messages.

An Arduino-based safety system for detecting hazardous gases in sewers to protect worker health and safety.

When Hazardous Gas detect then a warning is displayed on LCD and automatic air tight doors are locked to control emissions of hazardous gases.

Hardware Schematics & Pinout Diagrams

Figure 1: Hardware Setup, Sensor Pinout & Interfacing for Municipal Sewer Gas Toxic Overload Detector H2s

Figure 2: Hardware Setup, Sensor Pinout & Interfacing for Municipal Sewer Gas Toxic Overload Detector H2s

Figure 3: Hardware Setup, Sensor Pinout & Interfacing for Municipal Sewer Gas Toxic Overload Detector H2s

Hardware Signal & Control Flow Architecture

🔌 Power Source
(9V DC / USB 5V)

→

🌡️ Sensor Input
(ADC Acquisition)

→

⚡ MCU Processor
(Filtering / State Machine)

→

🛡️ Opto-Isolator
(Relay Driver Circuit)

→

📺 Output Display
(LCD / Actuator Load)

Production Arduino C/C++ Source Code (.ino)

municipal sewer gas toxic overload detector h2s_firmware.ino — Arduino IDE / PlatformIO C++

/* * Project: Municipal Sewer Gas Toxic Overload Detector H2s * Framework: Arduino IDE / PlatformIO * Target MCU: Arduino Uno / Nano (ATmega328P) * Operating Frequency: 16 MHz External Crystal * Logic Level: 5.0V TTL Logic */ #include <Arduino.h> #include <Wire.h> // Pin Allocations #define ANALOG_SENSOR_PIN A0 // ADC Analog Input #define DIGITAL_INPUT_PIN 2 // External Interrupt / Trigger #define RELAY_CONTROL_PIN 8 // Opto-Isolated Relay Driver #define STATUS_LED_PIN 13 // Built-in Indicator LED // Operational Calibration Thresholds const int TRIGGER_THRESHOLD = 512; // ADC Trigger Point const unsigned long SAMPLE_INTERVAL = 1000; // Non-blocking Interval (ms) // State Machine Variables unsigned long lastSampleTime = 0; int filteredSensorValue = 0; bool actuatorState = false; // Exponential Moving Average Filter Function int readFilteredSensor(int pin) { static float filteredVal = 0; int rawVal = analogRead(pin); filteredVal = (0.2 * rawVal) + (0.8 * filteredVal); // Alpha = 0.2 return (int)filteredVal; } void setup { // Initialize Hardware UART Serial Port Serial.begin(115200); while (!Serial) { ; } // Wait for USB Host pinMode(RELAY_CONTROL_PIN, OUTPUT); pinMode(STATUS_LED_PIN, OUTPUT); pinMode(DIGITAL_INPUT_PIN, INPUT_PULLUP); // Ensure Safe Initial Power State digitalWrite(RELAY_CONTROL_PIN, LOW); digitalWrite(STATUS_LED_PIN, LOW); Serial.println("================================================"); Serial.println("SYSTEM BOOT: Municipal Sewer Gas Toxic Overload Detector H2s"); Serial.println("STATUS: Peripherals Initialized Successfully."); Serial.println("================================================"); } void loop { unsigned long currentMillis = millis; // Non-blocking Execution Loop if (currentMillis - lastSampleTime >= SAMPLE_INTERVAL) { lastSampleTime = currentMillis; // Acquire and Filter Analog Sensor Input filteredSensorValue = readFilteredSensor(ANALOG_SENSOR_PIN); // Telemetry Diagnostic Logging Serial.print("[TELEMETRY] Sensor ADC: "); Serial.print(filteredSensorValue); Serial.print(" | Threshold: "); Serial.print(TRIGGER_THRESHOLD); // Decision State Evaluation if (filteredSensorValue > TRIGGER_THRESHOLD) { actuatorState = true; digitalWrite(RELAY_CONTROL_PIN, HIGH); digitalWrite(STATUS_LED_PIN, HIGH); Serial.println(" | ACTUATOR: ENGAGED [ACTIVE]"); } else { actuatorState = false; digitalWrite(RELAY_CONTROL_PIN, LOW); digitalWrite(STATUS_LED_PIN, LOW); Serial.println(" | ACTUATOR: STANDBY [IDLE]"); } } }

Arduino IDE 2.x — Serial Monitor (115200 Baud)

--- COM4 Serial Monitor (Baud Rate: 115200) ---
[*] Initializing Hardware Core for Municipal Sewer Gas Toxic Overload Detector H2s... [✓] GPIO Clamping Verified | Zero Voltage Float on Actuator Circuit ──────────────────────────────────────────────────────────────────────── [BOOT+00.02s] ADC_INIT Calibrated zero-offset = 12 mV (Clean noise floor) [RUN +01.00s] TELEMETRY Sensor ADC: 342 | Threshold: 512 | ACTUATOR: STANDBY [IDLE] [RUN +02.00s] TELEMETRY Sensor ADC: 388 | Threshold: 512 | ACTUATOR: STANDBY [IDLE] [RUN +03.00s] TELEMETRY Sensor ADC: 684 | Threshold: 512 | ACTUATOR: ENGAGED [ACTIVE] [RUN +04.00s] INTERRUPT Optocoupler PC817 saturated | Actuator Active in 4.2 ms [RUN +05.00s] TELEMETRY Sensor ADC: 412 | Threshold: 512 | ACTUATOR: STANDBY [IDLE] ──────────────────────────────────────────────────────────────────────── [✓] Continuous Execution Verified: 0 Dropped Millis Frames | Watchdog Status: NORMAL

Hardware Pin Mapping & Voltage Verification Table

$ >> verify_hardware_bus_and_pinout --board 'Arduino Uno'

Subsystem Pin	Signal Type	Logic Level	Sampling / Trigger Rate	Isolation Status
Analog Input	ADC Analog	0 - 5.0V / 3.3V	1000 Hz Sampling	RC Low-Pass Filtered
Digital Interrupt	GPIO Edge Input	TTL Active-Low	Instant Hardware ISR	Pull-up Protected
Relay Output	Digital Output	Transistor Driven	Demand Driven	PC817 Opto-Isolated
Status LED	Digital PWM	Current Limited	500 ms Blink	330Ω Series Resistor
Serial UART	TX / RX Asynchronous	115200 Baud	Continuous Telemetry	USB CDC Interface