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feat: Implement MQ-135 Gas Sensor (#3244)
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Lines changed: 780 additions & 48 deletions

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‎assets/images/mq_135_gas_sensor.png‎

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‎lib/l10n/app_en.arb‎

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@@ -681,7 +681,16 @@
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"comingSoon": "Coming Soon",
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"startRecording": "Start Recording",
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"stopRecording": "Stop Recording",
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"tsl2561": "TSL2561",
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"gasSensorGuideIntro": "To use this instrument, you need an MQ-135 semiconductor gas sensor.",
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"gasSensorGuideDetail": "The MQ-135 is primarily intended for detecting flammable gases and broad air quality, but its readings can be mathematically translated to estimate CO2 Parts Per Million (PPM).",
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"gasSensorGuideConnectLabel": "How to connect:",
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"gasSensorGuideConnectStep1": "1. Connect the PSLab +5V pin to the sensor's VCC pin.",
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"gasSensorGuideConnectStep2": "2. Connect the PSLab GND pin to the sensor's GND pin.",
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"gasSensorGuideConnectStep3": "3. Connect the PSLab CH1 pin to the sensor's Analog Out (A0) pin.",
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"gasSensorGuideWarning": "Note: Readings are estimated based on default load and baseline resistances and assume a fresh air environment during calibration.",
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"ppmCO2" : "PPM CO₂",
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"noGasSensor" : "Gas Sensor Unavailable Please connect Gas Sensor",
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"tsl2561" : "TSL2561",
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"full": "Full Spectrum",
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"infrared": "Infrared",
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"infraredRaw": "Infrared (raw)",

‎lib/main.dart‎

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@@ -17,6 +17,7 @@ import 'package:pslab/view/accelerometer_screen.dart';
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import 'package:pslab/view/barometer_screen.dart';
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import 'package:pslab/view/connect_device_screen.dart';
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import 'package:pslab/view/faq_screen.dart';
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import 'package:pslab/view/gas_sensor_screen.dart';
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import 'package:pslab/view/gyroscope_screen.dart';
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import 'package:pslab/view/instruments_screen.dart';
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import 'package:pslab/view/logged_data_screen.dart';
@@ -142,6 +143,8 @@ class MyApp extends StatelessWidget {
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const _LocaleAware(child: SoundMeterScreen()),
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'/thermometer': (context) =>
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const _LocaleAware(child: ThermometerScreen()),
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'/gassensor': (context) =>
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const _LocaleAware(child: GasSensorScreen()),
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'/sensors': (context) =>
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const _LocaleAware(child: SensorsScreen()),
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'/experiments': (context) =>

‎lib/providers/gas_sensor_state_provider.dart‎

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@@ -0,0 +1,212 @@
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import 'dart:async';
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import 'dart:math';
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import 'package:fl_chart/fl_chart.dart';
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import 'package:flutter/material.dart';
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import 'package:pslab/others/logger_service.dart';
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import 'package:pslab/communication/science_lab.dart';
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import '../l10n/app_localizations.dart';
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import 'locator.dart';
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class GasSensorStateProvider extends ChangeNotifier {
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AppLocalizations appLocalizations = getIt.get<AppLocalizations>();
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ScienceLab? _scienceLab;
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double _currentPpm = 0.0;
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Timer? _readTimer;
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final List<double> _ppmData = [];
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final List<double> _timeData = [];
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final List<FlSpot> _gasChartData = [];
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double _startTime = 0;
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double _currentTime = 0;
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final int _maxLength = 80;
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double _ppmMin = double.infinity;
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double _ppmMax = 0;
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double _ppmSum = 0;
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int _dataCount = 0;
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bool _isSensorAvailable = false;
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bool _isInitialized = false;
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bool _isFetching = false;
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bool _isCalibrating = false;
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final double _rLoad = 10.0;
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double _r0 = 41.7;
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final double _vcc = 5.0;
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final double _paramA = 109.0;
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final double _paramB = -2.88;
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double get _correction {
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double t = 20.0;
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double h = 0.65;
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double a = 3.28e-4;
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double b = -2.55e-2;
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double c = 1.38;
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double d = -2.24e-1;
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return (a * pow(t, 2)) + (b * t) + c + (d * (h - 0.65));
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}
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double _calculateRs(double voltage) {
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if (voltage <= 0.01) voltage = 0.01;
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return ((_vcc / voltage) - 1) * _rLoad / _correction;
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}
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Future<void> initializeSensors() async {
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if (_isInitialized) return;
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try {
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_scienceLab = getIt.get<ScienceLab>();
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if (_scienceLab != null && _scienceLab!.isConnected()) {
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_isSensorAvailable = true;
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_startTime = DateTime.now().millisecondsSinceEpoch / 1000.0;
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_isCalibrating = true;
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notifyListeners();
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await calibrateInFreshAir();
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_isCalibrating = false;
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_startReadingGasData();
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logger.d('Gas sensor initialized successfully');
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} else {
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_isSensorAvailable = false;
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logger.w("ScienceLab not connected");
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}
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_isInitialized = true;
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notifyListeners();
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} catch (e) {
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logger.e("Error initializing gas sensor: $e");
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_isSensorAvailable = false;
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_isInitialized = true;
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notifyListeners();
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}
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}
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Future<void> calibrateInFreshAir() async {
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if (_scienceLab == null || !_scienceLab!.isConnected()) return;
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List<double> rsReadings = [];
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for (int i = 0; i < 10; i++) {
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double volt = await _scienceLab!.getVoltage(appLocalizations.ch1, 1);
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if (volt > 4.99) volt = 4.99;
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double rs = _calculateRs(volt);
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rsReadings.add(rs);
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await Future.delayed(const Duration(milliseconds: 100));
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}
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double avgRs = rsReadings.reduce((a, b) => a + b) / rsReadings.length;
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double ratioFactor = pow((400.0 / _paramA), (1.0 / -_paramB)).toDouble();
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_r0 = avgRs * ratioFactor;
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notifyListeners();
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}
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void _startReadingGasData() {
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_readTimer?.cancel();
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_readTimer =
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Timer.periodic(const Duration(milliseconds: 2000), (timer) async {
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if (!_isSensorAvailable ||
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_scienceLab == null ||
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_isFetching ||
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_isCalibrating) {
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return;
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}
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_isFetching = true;
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try {
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double volt = await _scienceLab!.getVoltage(appLocalizations.ch1, 1);
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if (volt > 4.99) volt = 4.99;
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double rs = _calculateRs(volt);
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double ratio = rs / _r0;
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double ppm = _paramA * pow(ratio, _paramB);
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if (ppm < 0 || ppm.isNaN) ppm = 0;
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if (ppm > 10000) ppm = 10000;
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logger.d(
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"READING: Volt: ${volt.toStringAsFixed(3)}V | Rs: ${rs.toStringAsFixed(2)} | R0: ${_r0.toStringAsFixed(2)} | Ratio: ${ratio.toStringAsFixed(3)} | Est PPM: ${ppm.toStringAsFixed(1)}");
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_currentPpm = ppm;
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_currentTime =
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(DateTime.now().millisecondsSinceEpoch / 1000.0) - _startTime;
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_updateData();
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notifyListeners();
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} catch (e) {
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logger.e("Gas sensor read error: $e");
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} finally {
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_isFetching = false;
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}
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});
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}
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void disposeSensors() {
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_readTimer?.cancel();
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_isInitialized = false;
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}
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@override
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void dispose() {
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disposeSensors();
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super.dispose();
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}
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void _updateData() {
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_ppmData.add(_currentPpm);
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_timeData.add(_currentTime);
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_ppmSum += _currentPpm;
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_dataCount++;
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if (_ppmData.length > _maxLength) {
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final removedValue = _ppmData.removeAt(0);
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_timeData.removeAt(0);
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_ppmSum -= removedValue;
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_dataCount--;
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}
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if (_ppmData.isNotEmpty) {
181+
_ppmMin = _ppmData.reduce(min);
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_ppmMax = _ppmData.reduce(max);
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}
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_gasChartData.clear();
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for (int i = 0; i < _ppmData.length; i++) {
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_gasChartData.add(FlSpot(_timeData[i], _ppmData[i]));
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}
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}
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double getCurrentPpm() => _currentPpm;
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double getMinPpm() => _ppmMin == double.infinity ? 0 : _ppmMin;
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double getMaxPpm() => _ppmMax;
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double getAveragePpm() => _dataCount > 0 ? _ppmSum / _dataCount : 0.0;
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List<FlSpot> getGasChartData() =>
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_gasChartData.isEmpty ? [const FlSpot(0, 0)] : _gasChartData;
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int getDataLength() => _gasChartData.length;
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double getCurrentTime() => _currentTime;
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double getMaxTime() => _timeData.isNotEmpty ? _timeData.last : 0;
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double getMinTime() => _timeData.isNotEmpty ? _timeData.first : 0;
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bool isSensorAvailable() => _isSensorAvailable;
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bool isInitialized() => _isInitialized;
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bool isCalibrating() => _isCalibrating;
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double getTimeInterval() {
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if (_currentTime <= 10) return 2;
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if (_currentTime <= 30) return 5;
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if (_currentTime <= 80) return 10;
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return 20;
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}
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}

‎lib/theme/colors.dart‎

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@@ -91,3 +91,6 @@ Color buttonDisabledColor = Color.fromARGB(255, 240, 162, 162);
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Color optionDisabledColor = Colors.black38;
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Color waveGeneratorPropTextColor = Colors.deepOrange;
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List<Color> stepCompletedColor = [Colors.green.shade400, Colors.green.shade600];
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const Color gaugeGradientStart = Color(0xFF40C4FF);
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const Color gaugeGradientCenter = Color(0xFF00B0FF);
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const Color gaugeGradientEnd = Color(0xFF0091EA);

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