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sensor:scd [2026/04/15 16:59] – created vamsansensor:scd [2026/04/15 17:34] (current) – vamsan
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-====== lamaPLC project: Sension SCD  ====== +====== lamaPLC project: Sension SCD CO² measurement module ====== 
-{{ :sensor:scd30.png?120|AHT10 Modul}}+{{ :sensor:scd30.png?120|SCD 30 Modul}}
  
-The primary difference between these Sensirion sensors is the measurement technology, which directly impacts their size and power consumption. The SCD30 uses traditional NDIR (Non-Dispersive Infrared) technology, while the SCD40/41 series uses a newer, miniaturized Photoacoustic principle. +The main distinction between these Sensirion sensors lies in their measurement technology, which affects their size and power use. The **SCD30** employs conventional **NDIR** (//Non-Dispersive Infrared//) technology, whereas the **SCD40/41** series utilises a more recent, compact Photoacoustic principle. 
  
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 ^Voltage|3.3V – 5.5V|2.4V – 5.5V|2.4V – 5.5V| ^Voltage|3.3V – 5.5V|2.4V – 5.5V|2.4V – 5.5V|
 ^Power (avg)|~19 mA|~15 mA|~0.5 mA (Low Power Mode)| ^Power (avg)|~19 mA|~15 mA|~0.5 mA (Low Power Mode)|
-^Interface|[[com:basic_i2c|I²C]], [[com:basic_uart|UART]], PWM|[[com:basic_i2c|I²C]]|[[com:basic_i2c|I²C]]|+^Interface|[[com:basic_i2c|I²C]] (Address **0x61**), [[com:basic_uart|UART]], PWM|[[com:basic_i2c|I²C]]|[[com:basic_i2c|I²C]]| 
 +^Operating Temperature|0°C to 50°C||| 
 + 
 +**Key Differences** 
 + 
 +  * **Form Factor:** The SCD40/41 is approximately ten times smaller than the SCD30, making it well-suited for compact wearables or integrated smart home devices.  
 +  * **Precision vs Size:** The SCD30 generally offers slightly better accuracy and stability over extended periods, thanks to its dual-channel NDIR design, which naturally compensates for sensor drift.  
 +  * **Power Efficiency:** For battery-powered devices, the SCD41 is the preferred choice, featuring a "Single Shot" mode that significantly reduces power consumption compared to the SCD30 or SCD40.  
 +  * **Mounting:** The SCD40/41 is an SMD (Surface-Mount Device) component suitable for reflow soldering and mass production. In contrast, the SCD30 is usually hand-soldered or connected via pins.
  
 {{page>:tarhal}} {{page>:tarhal}}
  
-===== Wiring =====+===== SCD30 ===== 
 +The SCD30 is a high-precision, 3-in-1 sensor module from Sensirion that measures Carbon Dioxide (CO²), Temperature, and Relative Humidity. It is considered a "true" CO² sensor because it uses Non-Dispersive Infrared (NDIR) technology to directly measure CO² molecules, rather than approximating levels from other gases.
  
 +**Key Features & Technology**
  
 +  * **Dual-Channel Detection:** It uses a dedicated reference channel to compensate for long-term drift, ensuring superior stability over its 15-year lifetime.
 +  * **Integrated Compensation:** The module uses its built-in temperature and humidity data to internally calibrate and normalise the CO2 readings.
 +  * **Self-Calibration Options:** Supports Automatic Self-Calibration (ASC), which resets the sensor's baseline when exposed to fresh air (~400 ppm) regularly, or Forced Recalibration (FRC) for manual setup.
 +  * **Adjustable Sampling:** While the default interval is 2 seconds, it can be set to 1-1800 seconds to reduce power consumption in battery-powered projects.
 +
 +==== SCD30 Pinout ====
 +{{ :sensor:scd30_pinout.png|}}
 +^Pin^Name^Description^Logic Level|
 +^1|VDD|Supply Voltage (3.3V – 5.5V)|—|
 +^2|GND|Ground|—|
 +^3|TX / SCL|Modbus Transmit / I²C Clock|3.0V (internal pull-up)|
 +^4|RX / SDA|Modbus Receive / I²C Data|3.0V (internal pull-up)|
 +^5|RDY|Data Ready (High when new data is available)|3.0V|
 +^6|PWM|Pulse Width Modulation output|3.0V|
 +^7|SEL|Interface Select (Floating/GND = I²C; High = Modbus)|< 4.0V|
 +
 +**Key Wiring Notes**
 +
 +  * **Internal Pull-ups:** The module has internal 45 kΩ resistors connected to a 3V supply for the I²C lines. 
 +  * **Voltage Warning:** The module can be powered with 5V, but the SCL/SDA logic pins operate at 3V. When using a 5V microcontroller like an Arduino Uno, a level shifter is strongly advised to prevent damage to the sensor. 
 +  * **Interface Selection:** For I²C (the standard mode), leave the SEL pin floating or connect it to Ground. To use Modbus, connect the SEL pin to VDD via a voltage divider, ensuring the voltage does not exceed 4V.
 +
 +==== SCD30 Arduino example code ====
 +To use the SCD30 with an Arduino, the **SparkFun SCD30** Arduino Library and the Adafruit SCD30 Library are the most common choices.
  
 <code c> <code c>
 +#include <Wire.h>
 +#include "SparkFun_SCD30_Arduino_Library.h" //
 +
 +SCD30 airSensor;
 +
 +void setup() {
 +  Wire.begin();
 +  Serial.begin(9600);
 +  
 +  if (airSensor.begin() == false) {
 +    Serial.println("Sensor not detected. Check wiring!");
 +    while (1);
 +  }
 +  Serial.println("SCD30 detected!");
 +}
 +
 +void loop() {
 +  if (airSensor.dataAvailable()) {
 +    Serial.print("CO2(ppm): ");
 +    Serial.print(airSensor.getCO2());
 +    Serial.print(" Temp(C): ");
 +    Serial.print(airSensor.getTemperature(), 1);
 +    Serial.print(" Humidity(%): ");
 +    Serial.println(airSensor.getHumidity(), 1);
 +  }
 +  delay(2000); // Sensor updates every 2 seconds by default
 +}
  
 </code> </code>