Webserver for the Greenhouse Gas Sensors

🔘 Carbon Dioxide, CO2, and Methane, CH4, are present in the atmosphere in part due to burning fossil fuels 🏭, and farming 🐂( particularly livestock ). They are potent 'greenhouse' gases as they have a significant impact on global warming, which drives climate change.

A new WiFi version of the Greenhouse Gas Monitoring System, ( 📅28.07.2022, 5.01.2023 & 18.02.2024 ) has been completed, incorporating a web 🕸 server having an embedded webpage. The firmware and webpage were developed along very similar lines to that used recently with the "Solarometer" 🔅( 📅13.10.2024 ); the latter using html and CSS *.

However, as the outdoor location of the gas sensors, ( type MQ-4 for CH4, type MQ-135 for CO2 ), will always be within the coverage area of an existing WiFi network access point, ( AP ), the system has been configured as a station ( STA ) on that network, and assigned the IP address 192.168.1.49.

Webpage opened in a smart phone's browser

The concentration ( parts per million, ppm ) measurements📏 are updated in real-time 🕔, and can be quickly viewed on a mobile device's🖁 browser, saving time over logging in to cloud ☁ based repositories, if historical data are not required.

Another way is to use the new SpacerLabs custom App "Greenhouse_Gas_Viewer v1.nn", for Android devices.

Displaying ppm measurements using the App

In this case the webpage itself ( /root directory ) is not displayed. Only the sub-directories ( /CH4ppm & /CO2ppm ), which are the place-holders for the CH4 and CO2 concentration data, are read by the App and the data held therein displayed.🔘

* CSS = Cascading Style Sheets - used to add style attributes to an html document.

Solarometer 🔆

🔘The Ultra Violet Radiation Meter 𐆁- UVRM, (📅 see 23-3-2023), has been improved with some new features and functionality, and also given a new name -  "Solarometer".

There is a new version of the BluetoothⓇ mobile 📱App, now called "Solar_Meter", ( as not only the UV index is being displayed ), having more on-screen notifications e.g., 'About' screen, as well as the new signal strength indicator and a different appearance.

Solar_Meter App user interface

The Wifi firmware has also been upgraded. The Solarometer hosts a webserver with a basic embedded web 🕸 page, ( written in html, css & JavaScript ), and automatically configures itself as a WiFi soft access point, ( IP 192.168.4.1, SSID "SpacerLabs WiFi Sensors" ). This was originally developed for the UVRM in 📅 January 2021 as a prototype only. At that time "http" server-client communication protocol was adopted, which required a page refresh to initiate an http request to get a new UV measurement value. The Solarometer, however, uses "Asynchronous JavaScript & XML" ( 'AJAX' ) protocol for near real-time updating of the measured 📏light intensities on the webpage opened in the client's browser.

Webpage displayed on a phone's browser

Alternatively, the new SpacerLabs 'VISUVIR_Viewer' WiFi App can be used to get and display the sun-light ☼ intensities , but still employing the original http protocol.

VISUVIR_Viewer App user interface

The 🔗  Node-Red 🟥visual programming tool contains an 'http request' node. A 'flow' 🔀was created to read data from 192.168.4.1 and update the readings 📈 on a dashboard.

SpacerLabs Node-Red dashboard for the Solarometer

Orange, blue, grey, yellow, white and translucent have been added to the choice of colours 🌈for the 3-D printed enclosure.

The Solarometer is intended for hand-held outdoor ⛅use; wireless version in range of client devices. It is powered by an internal 1000mAh 3.7V Li-Po rechargeable 🔋battery.

Looking ahead 📅,  the Solarometer, and/or new WiFi projects, will make use of websockets servers and protocol for even faster operation.

꩜ 

Note:  css = cascading style sheets.

Node-Red dashboard for the PMS5003

🔘The Node-Red 🟥browser based visual programming tool was first used at SpacerLabs in 📆March 2021 and then several times since then, usually to trigger actions and ⏰alerts, e.g., send an email 📧, when a sensor measurement 📏exceeds a threshold. If the measurement itself were needed it could be found under the debug tab in the sidebar on the right of the workspace ( see image below ). But 🔗 Node-Red also provides a 'dashboard' option for better visualisation of the measurement 📏data. 

A Node-Red 'flow' 〰, ( similar to the one from 📅29 February for the AQM ), was designed, but instead using measurements from the PMS5003 particulate matter sensor⛬ ( see 🗓 8 April & 16 June ). However, only the PM0.3 particles🏁 per deci-litre ( ppdl ) measurement has been extracted for this demonstration exercise.

Node-Red workspace, (L) node palette, flow, (R) debug sidebar

The node 🎨palette has been scrolled down to show all those relevant to the dashboard design. Each node represents a different widget either for displaying the sensor measurement 📏or for user input. Five have been selected and connected into the flow 🔀 as shown above. After deploying the flow, the dashboard can be opened in another browser tab by appending /ui to the address, ( see image below, click to enlarge ).

Node-Red dashboard

The widgets have been arranged vertically; starting from the top: text widget, gauge widget, compass 🧭widget, & chart 📈widget. The fifth widget is  a pop-up notification which only appears when a new measurement is received.🌀

Part of dashboard enlarged to show notification pop-up

IoT Cloud Platforms☁

🔘Several previous posts have mentioned the 🔗Ubidots and 🔗Thingspeak IoT cloud ☁ platforms, conveniently accessed from a web-browser, that have been used with some of our sensor based projects to capture, visualise and analyse 💹 the sensor measurements. Two others, 'Arduino IoT Cloud' and 'Thingsboard', have been found and tried out in conjunction with the PMS5003 Particle Concentration Sensor; ( see 8 April & 16 June ). Setting up was quick and straightforward, following the typical process for such platforms of creating an IoT 'thing', assigning 'variables', associating a 'device', programming & connecting the device, & designing a 'dashboard'; our device is a "D1 Mini Esp32" micro-controller board.

The 🔗Arduino IoT Cloud is an entirely cloud based platform, including an editor for writing and compiling the project firmware, which can then be downloaded from the cloud ( depending on the subscription plan ) to the device, from anywhere in the world 🌐. Nothing is required to be installed locally on a pc 💻or connected to it other than a browser and internet connection. The dashboard shown in the image below is constrained by a maximum of  5 cloud variables under the no-time-limit free 🆓 plan. In general, the widgets to populate the dashboard tend to be the standard, classic ones.

Example of Arduino IoT Cloud dashboard - desktop version

An App "Arduino IoT Remote" on a mobile device 📱provides a mobile friendly version of the dashboard.

An account was opened for the 30 day free trial period of the 🔗Thingsboard cloud 'Maker' version. There is a large selection of attractive widgets for the dashboard, sorted by various categories. For example, under the "Air 🜁 Quality"  category there are numerous widget designs specifically for the measurement data relevant to air-quality. Some were chosen for the dashboard shown in the image below

Example of a Thingsboard dashboard

🌀IoT = Internet of Things.      

PMS5003, colour display, BluetoothⓇ & cloud

🔘The project involving the 🪴Plantower 🗼PMS5003 digital Particle Concentration Sensor, described in the previous post on 8 April, has progressed further with the addition of embedded firmware using an  ESP32 microcontroller development board, a colour display, and BluetoothⓇ or Wi-Fi options.

The display is a colour TFT touch sensitive display with resolution 240 x 320 pixels, ( see image below ), last used on 5 January 2023.

Version with display using prototyping board 

Particle number per 0.1 litre ( ppdl ) of air and density ( ug/m^3 ) for various particle diameters Ø in microns are displayed. The "Air Quality Index  - AQI" ( 0 to 500 ) is derived from the PM2.5 density figure.  The "Quality" label which is assigned ( GOOD, MODERATE etc ) depends on the AQI. This is the method in common use internationally to quantify air pollution 😷 due to particulates. The touch-sensitive 'buttons' near the lower edge of the display give full control of the various modes of operation of the PMS5003. Some modes are initiated by sending instructions to the PMS5003 by serial data, and some are hardwired.

The ESP32 has a built-in BluetoothⓇ Low Energy, ( BLE ), module. The particulate matter data and mode functions as described above are available using the BluetoothⓇ version and the SpacerLabs custom Android App, "SpacerLabs PMD_Viewer vn.nn", on a compatible mobile device 📱having BluetoothⓇ enabled.

App user interface opened

Ubidots is a cloud hosted repository for measurement data. It was featured in this blog before, on 29 February,  then being used with the AQM device. The ESP32 also has a built-in Wi-Fi module. So a version of the firmware including Wi-Fi functionality was written, enabling the PMS5003 measurement data to be uploaded to the cloud.

PMS5003 Ubidots dashboard - ( click to enlarge )

An 'Air Quality' device, i.e., the Plantower PMS5003 Particulate Matter Sensor', has been added to our Ubidots dashboard together with several new widgets for displaying the particle measurements. A similar exercise was carried out with Thingspeak cloud; see also 18 February 2024. Search for channels by user ID spacerlabs to see the result.

The serial communications interface ( see 8 April 2024 ) is still retained, and is a common feature of all versions. 

PMS5003 Digital Particle Concentration Sensor

🔘The SpacerLabs domestic 'Air Quality Monitor' ( AQM ) 🏭 with multi-sensor support posted on 15.03.2023, ( updated 29.02.2024 ) is based on the Cubic PM1006 infra-red LED particle sensor module.  Another type of  particle sensor is the 🪴 Plantower 🗼PMS5003.  It uses a laser source, is capable of detecting particles down to ⌀0.3 microns in size, and measures some additional  values compared to the PM1006 as well as being approximately twice as accurate. One has been obtained as an individual item, ( not part of an AQM product, filtration or ventilation equipment etc ), and is being tried out.

The measurements made by the PMS5003 are sent periodically ⏲ as 32 bytes of data over a UART serial interface at a data rate of 9600 bits/sec. A UART to USB protocol converter dongle provides a virtual COM port on a computer allowing the data to be displayed on a pc if there is a usb cable connecting 🔗both and a serial terminal program is running. 

Left - PMS5003, Right - UART to USB dongle

We wrote a serial terminal application specifically for the PMS5003, called 'PMS5003_Serial' , in order to demonstrate the operation of the PMS5003, ( image below ).

PMS5003_Serial software receiving & displaying data

The received raw serial data are displayed in hexadecimal and decimal, then parsed in software to extract the bytes of interest containing data relating to particulate matter🦠  mass concentration ( ug/m^3 ) and particles per deci-litre, ppdl, ( 0.1 litre ) of air 🜁 , sorted according to size in microns. The AQI ( range 0-500 ) and air quality level are also given.

This project might be developed further by providing embedded control, a touch sensitive colour display, Bluetooth, App for a mobile device and a 3-D printed case.

 

UART = Universal Asynchronous Receiver Transmitter.

AQI = Air Quality Index

 

 

PM2.5 data from AQM now on the cloud

🔘Particulate Matter ㏘, PM2.5, data can now be uploaded 🖧 to the Ubidots cloud  ☁ from the Air Quality Monitor ( AQM ); see 15.03.2023. The Ubidots Ů platform provides visualisation / analysis of data from IoT sensors, also generating events, alerts, actions etc if required. We are already using this platform in conjunction with the Greenhouse Gas Monitoring system ( see 28.07.2022 ) and a soil moisture meter. On this occasion, with the AQM,  Node-Red is being used for alerts⏰.Two new widgets to display the PM2.5 concentration value have been added to an existing SpacerLabs Ubidots dashboard. The colours used for the air-quality levels ( good, OK, poor ) on the gauge widget match those used on the coloured LED indicator on the front of the AQM. 

Part of the dashboard showing the new widgets for PM2.5

Using the Node-Red 🟥 application, function 'nodes' are linked by connecting inputs to outputs and on-line services to create a 'flow' to perform task(s) using a browser based workspace. We have used it previously with the UVRM ( see 23.03.2023 ) and a soil moisture meter. The AQM flow ( image below ) starts by subscribing to the AQM PM2.5 data on Ubidots cloud using MQTT ( blue node ) and ends by triggering an email 📧 to be sent when the PM2.5 level exceeds 85 ug/m3; classified as level 'high' and air 🜁 quality 'poor'.

Node-Red 'flow' to trigger an email warning of poor air quality

It can be seen under the 'Debug' tab that an email 📧is indeed sent when PM2.5 >85; otherwise only the value ( if changed ) is reported. The email topic reads "SpacerLabs AQM - PM2.5 Alert " and the message reads "The SpacerLabs AQM has measured a PM2.5 level >85 (High) Air-Quality category - Poor. (Timestamp)". Even though the AQM may not be visible, an immediate audible notification is given by a smart phone when the email is received. 🔲

PM2.5 = Particulate Matter size 2.5 micron

MQTT = Message Queued Telemetry Transport

IoT = Internet of Things

🏭Greenhouse Gas Monitor - Real Time Data

       🔘The SpacerLabs "Greenhouse Gas Monitoring System" 🟩 was described on 28.07.2022 & 05.01.2023 🗓. Periodically since then it has been used to measure the outdoor concentrations of two potent green-house gases, Methane and Carbon Dioxide, in close proximity to "Spacerowa Laboratories" at 3m above ground level.  Methane ( CH4 ) and Carbon Dioxide ( CO2 ) concentration data in parts per million are now downloaded here every 15 minutes from the SpacerLabs Greenhouse Gas Monitor channel on ThingSpeak cloud ☁ for IoT sensor projects.

It has been noticed that increased concentration of methane coincides with wet weather conditions and vice-versa. According to NASA data, atmospheric concentration of CO2 was 416ppm in 2021, and CH4 was 1.8922ppm in 2020.

Lower left MQ-4 sensor, lower right MQ-135 sensor

The image above shows the outdoor part of the system with the two gas sensors, MQ-4 ( methane ) and MQ-135 ( carbon dioxide ), mounted in a weather-proof junction box,  ( cover removed ).

The blue trim-pot on each sensor breakout board can be used to set a concentration threshold level to trigger an alarm ⏰ and illuminate 💡 a LED ( just visible in the image ). Although active, the alarm condition is currently not being extended back to the micro-controller situated indoors for processing. 🔲

 

True RMS Voltmeter ⌁

⚡The Root Mean Square ( RMS ) voltage is a useful value to measure as it is related to the power  ( 'heating effect' ) of the voltage. The SpacerLabs "RMSDC-1" voltmeter described here is able to measure the true RMS value of complex periodic voltage waveforms, ( not just sinusoidal ∿ ), up to frequencies of  typically 8MHz, and even if a DC offset level is present.

Measuring the output voltage of a 3V DC precision source

Central to the operation of the RMSDC-1 is a highly accurate RMS to DC converter chip which produces a DC voltage equivalent to the RMS value of the input voltage. This DC voltage is sampled by a separate 10-bit analogue to digital converter ( ADC ) so that the voltage can be displayed. Also a dB output is available which has been calibrated to give the dB value of the input voltage being measured relative to 1V ( 1V = 0dBV ). For DC voltages the RMS value is the same as the DC value. So the RMSDC-1 can be used as a DC voltmeter. Both AC and DC input coupled signals can be measured; the latter allowing any DC offset to be retained. An active analogue filter of the Sallen-Key type can switched in to reduce any potential inaccuracy due to AC ripple at 2X input frequency.

An attractive 3-D printed front panel can be fitted

A front panel has been designed and printed to give the RMSDC-1 a very smart appearance. The front panel also serves to support the RMSDC-1 vertically. The display module is a 2X16 LCD with a white or yellow/green back-light. 

 

AD9850 DDS Module with mobile App configurator

📶The Analog Devices Inc. AD9850 is a 32bit CMOS Direct Digital Synthesiser ( DDS ) device. Evaluation circuit boards with the device already mounted are widely available at low cost. However, in order to use the device ( perhaps only a quickly assembled frequency source is required ) a means still has to be provided of uploading to it 5 bytes of configuration settings, also a display to show the frequency and a rotary encoder for tuning. In the past at 'SpacerLabs' we have used a SPI-USB dongle and pc terminal software to acheive this.

📳A different and even more convenient method has recently been devised using an ESP32 micro-controller and our custom App for mobile devices📱called "DDSTerm". The App generates the 5 configuration bytes required from the user input frequency and phase data, then sends to the ESP32 using BluetoothⓇ. The ESP32 uploads the bytes using the SPI to the DDS board. The desired frequency [ ∿ ] is output. In the image example below frequency is 11.501MHz & bytes hexadecimal 178DD617C4.

App 'DDSTerm_v1.06' opened

The image below shows the hardware setup used during development, comprising a typical ESP32 micro-controller in a 3-D printed case connected to the AD9850 DDS evaluation board mounted on a test-jig. The test-jig is not essential as the DDS board has pin-strip headers.

(Left) AD9850 board on test-jig, (R) ESP32 micro-controller inside enclosure

𝌕The Android App "DDSTerm" and firmware for the ESP32 are available from us. Contact us by email or use the form below to receive more information. Note that AD9851 DDS boards are also supported.

SPI = Serial Peripheral Interface ( 3-wire bus )