pH Meter for Wine & Environmental Testing

🔘This pH meter, ( abbreviated PHM ), measures the pH# of liquids🫗 to determine the degree of acidity or alkalinity. The pH measurement range is from 0 to 14; pH<7 is acidic, pH=7 is neutral and pH>7 is alkaline. In addition to having uses in the environment🏞 for assessing water quality, the PHM was designed particularly for applications in winemaking🍷 to check if the pH of the 🍷wine lies within the optimum range of 3.0 to 3.4.

The complete PHM with probe connected - note the micro usb connector

The constituent parts of the PHM are the pH probe ( connected by cable terminated in a BNC connector ) plugged into the case which contains the probe control module, ų-controller and rechargeable 🔋battery. The probe, its control module and a ESP32 based ų-controller board are commercial items which are available for purchase from numerous vendors. The case is a custom SpacerLabs design and was 3-D printed. The ų-controller is programmed with custom SpacerLabs in-house software. The PHM is powered by an internal rechargeable 🔋battery, or externally via usb ( pc, power bank, usb charger etc ).

Internal view showing battery & (L) control module (R) ų-controller

Three versions of the PHM have been developed; 2 WiFi versions ( station or soft access point ) and a BluetoothⓇ ( BLE** ) version.

There is no integral display to display the pH measurements*. So instead the measurements are read from a user interface ( UI ) typically on a smart phone having wireless connectivity with the PHM, and either a 🕸web-browser or the custom SpacerLabs App "pH_Meter_vn.m" installed.

Before first use the PHM was calibrated using standard buffer solutions of pH4, 7 & 10. 

Though not necessary when the PHM is in normal use, serial data at 115200Bd can be displayed for diagnostic & development purposes by using a terminal emulation program e.g. SpecTecsTerm, on a pc💻 connected to the micro-usb connector, which is also used to charge the battery🔋. The PHM is declared as a virtual COM port.

The 📖User Manual can be downloaded 🔗here.🔲

 

# pH - hydrogen ion concentration, potential of hydrogen.

* A version with an integrated display is being considered for future development. Post a comment if you would like that.

** BLE - Bluetooth Low Energy.

Oven Temperature Checker - 2nd generation

🔲The original Spacerlabs "Oven Temperature Checker - OTC" appeared on this blog on📅 6 December 2021; but it's development actually began in 📅September 2017. To recap, it's purpose is to measure the air temperature🌡 of the internal cavity of a domestic oven ( non microwave ) to compare with the user set 🌡temperature. This 📮post describes the next generation OTC, and the differences. Many features are, however, retained; for example 2.4GHz BluetoothⓇ wireless 🛜connectivity ( using Bluetooth Low Energy - BLE*) is still used.

The OTC now has a custom 3-D printed case compatible with a terminated ( plug-in ) or unterminated ( hardwired ) Type-K thermocouple. The OTC is powered from an external power source, e.g., power bank, via the micro-usb socket.

Custom case, any colour possible, usb socket on rear, note thermocouple inputs

There is no integral display. The User Interface ( UI ) is the SpacerLabs custom app "OTC_Ui_v1.x" for a BluetoothⓇ enabled Android device. The OTC functions as a BluetoothⓇ server, advertising itself as "SPACERLABS_OTC". Connecting to the server with a paired BluetoothⓇ client device, ( e.g. smart phone having the app installed ), enables the OTC ready for use.

App icon attributed to 'Freepik'

App screen showing a completed measurement run

The App displays the version of the software uploaded to the OTC, real time 🕖clock ( RTC ), status of BluetoothⓇ connection, and received signal 🛜strength indication ( RSSI ) of the BluetoothⓇ signal. A pop-up ⚠alert appears if the 🛜signal is too weak. A measurement cycle, maximum duration ⏲10 minutes, can be started, paused or cleared by tapping the appropriate button. A 🌡temperature measurement is made every ⏲second and plotted. Instantaneous oven 🌡temperature, OTC 🌡temperature, elapsed ⏲time and average oven🌡 temperature over time are numerically displayed. The oven 🌡temperature, up to 240C, is plotted 📈against🕰 time. Any thermocouple faults which might occur are ⚠flagged; OC (open circuit), SCV (short to volts) & SCG (short to ground). Temperature measurements in serial form, data rate 115200Baud, can be accessed by connecting a pc running terminal emulation software to the micro-usb socket.🔳

 

The OTC 📖User Guide can be downloaded 🔗here.

*BLE is the low power variant of classic BluetoothⓇ.

PMD update - WiFi(SAP), Bluetooth & Battery

🔘The SpacerLabs " Particle Matter Detector - PMD" was last updated here on 📅17 June 2025. Since then Soft Access Point (SAP) 🛜WiFi ( websockets server ) & Bluetooth versions have been developed, also powered by an internal 🔋battery.

WiFi & Bluetooth versions have the same appearance

A 🕸webpage has been designed, using HTML, CSS & JavaScript, specifically for the new 🛜WiFi SAP option. But the 🕸webpage User Interface ( UI ) for the STN ( Station ) option has also been revised to include status information about the internal🔋battery.

WiFi SAP version webpage on a phone's browser

The SAP 🛜WiFi version has no internet 🖧connection - see top of above image. So the online libraries used for the chart📈 plotting and background image in the STN version are not accessible by the SAP version.

The UI of the Bluetooth version is the Spacerlabs custom app "PMD_Viewer" for a Bluetooth enabled Android📱device.

App opened on a smart-phone🖁

Both the WiFi & Bluetooth versions have an internal re-chargeable battery🔋 permanently connected as a power source. The 🔋battery is a Lithium-Ion Polymer ( LiPo ) 3.7V 620 mAh type. Therefore these two PMD versions can be used for a limited time, in a hand-held or stand-alone manner, without the need for an external power source and connecting cable. Battery charge level 🪫information is displayed by the UI. The 🔋battery is recharged in-situ via the micro-usb socket.

 

The latest version of the 🗐'PMD User Guide' can be downloaded 🔗here. 🔳

Solarometer & AQM conversion to Websockets

🔳Continuing with our plan to convert to 'Websockets' our 📶WiFi connected projects with web-page servers,  the🌞 'Solarometer' ( from 📅13.10.2024 & 23.03.2023 ) and😷 'Air Quality Monitor - AQM' ( from 📅15.03.2023 ) are the latest, and possibly the last, candidates for conversion; also getting redesigned webpages in the process.🔳

Webpage: solarometer5.html

Webpage: air-quality-monitor-v1.html

Upgrades to the Greenhouse Gas Monitor

🔘Our "Greenhouse Gas Monitoring System" measures the concentrations ( in parts per million, ppm ) of two potent greenhouse gases present in the atmosphere, Carbon Dioxide and Methane. The last upgrade added a webserver and embedded webpage ( 📅see 01.12.2024 ). 

The upgrade described here has replaced the original AJAX/HTTP webserver with a 'Websockets' server also incorporating a redesigned webpage, having more features and an attractive appearance; ( image below, click to enlarge ).

Webpage: gas-sensors-v2.html

The new features include displaying the WiFi signal level 📶to assist in choosing the location of the sensors, time-stamp provided by an NTP server, and a bar-chart 📊showing the recent history of the gas concentration measurements, updated in real-time every 🕞15 seconds.

Extensive use of graphics and images has contributed to the modern appearance of the new page design. The page's background image shows the outdoor unit which contains the two sensors; seen exposed to the atmosphere along the lower edge. The 'emojis' * which were included in the page design show some of the causes and consequences of these gases.🔘

NTP = Network Time Protocol.

* Emojis appear similar to images and icons but are characters from the UTF-8 character set.

New Webpage for the Remote Soil Moisture Meter

🔘A "Remote Soil Moisture Meter - RSMM" has been in operation during the summer 😎 months since before this blog began; prior to  📅December 2021.

RSMM deployed in a herb garden - note LoRa antenna & solar panel

The RSMM transmits a soil moisture🚰 measurement every 🕥 hour using "LoRa" * wireless 🗼data technology to a receiver 📻module located conveniently indoors, about 35 metres away.

Several variants of the 📻receiver module were made; in general having either 🛜WiFi or Bluetooth functionality, in addition to LoRa. One of the 🛜WiFi options hosts a webserver, with embedded webpage to display the moisture 📏 measurement. This is accessed from a 📱smart-phone, 💻pc etc, having a browser installed. The original, basic, webpage design from 📅2021 is shown in the image below.

Version 1 webpage displayed on a phone

Recently the webpage has been given an upgrade to v2. The much improved webpage was designed using HTML, CSS & Javascript and has been considerably enhanced compared with v1 with several new features, such as 🛜WiFi signal level 📶indicator, chart 📈of moisture measurements over 🕥12 hours updated in real-time, and a button to pop-up moisture level definitions. The appearance has been revised and modernised with graphics, especially with the background image of the RSMM itself, a browser page tab favicon, and the use of different coloured panels to separate elements. Version 2 ( June 2025 ) is shown for comparison in the image below.

V2 viewed on a pc browser

V2 will be uploaded to the receiver module next time the RSMM is deployed, and is operational.

The latest issue of the 'User Guide' can be downloaded 🔗here.

* 'LoRa' = 'Long Range' 🔲

PMD WiFi + Websockets, Webpage & Dashboard

🔘The 'PMD-Serial-UART', and 'PMD-Display' versions of our 'Particle Matter Detector' ( "PMD" ) were described in previous posts on 📅08.04.24, 16.06.24 & 01.01.25. A 🛜 'WiFi' version has now been added to the product range, which features an embedded 'Websockets Server' serving a webpage; ( enter websockets into the blog search bar to see examples of websockets servers & protocol ). Depending on the installed firmware the PMD can be configured as a Station on an existing 🛜WiFi network ( with or without a config web-portal ), or as a stand-alone Soft Access Point.

PMD - WiFi version: Note (L) air-intake & (R) micro-usb socket  

The webpage, ( designed using HTML, CSS, W3.CSS & JavaScript ), displays all the measurements made by the PMD's internal PMS5003 particle detector, ( particle density ug/m3, & particle number per deci-litre ppdl ), and additionally the 'Air Quality Index - AQI', and 'Air Quality Level - AQL', which are separately calculated from the concentration of 2.5 micron particles. All results are updated in real-time and displayed in tabular form on the webpage every second. There is also a bar meter showing the 🛜WiFi signal level, 🕓time/date stamp, and bar-chart 📊showing the recent history of the PM2.5 measurements. Tapping the 'show/hide levels' button opens a pop-up showing the AQL categories - 'Good, Moderate, Poor, Unhealthy, Very Unhealthy, Hazardous & Extreme '.

Webpage: particle-matter-detector-v3.html

The webpage in the image above was being displayed by a browser on a laptop, having navigated to IP:192.168.1.54. 

A dashboard for the PMD, ( designed with Node-Red ), is shown below. Not all the measurements have had a widget assigned in this example, which is simply for demonstration purposes. 🔲

PMD dashboard - reduced set of measurements displayed

Node-Red Dashboard for the PWM

🔘The "Node-Red " browser based visual programming environment has been used several times before. ( Use the search box to find out more about it and our previous related projects ). This time its dashboard feature is being used again in order to display in real-time the measurements being made by the "Plant Water Monitor - PWM" ( refer to last post 📅05.05.25).

A 'flow' was built-up by interconnecting nodes selected from the palette ( left sidebar ). The input to the flow is of course the measurements being sent by the PWM  'websockets' server. Fortunately the palette includes the node ( 'websocket in' ) to handle this ( highlighted in the image below ) ! 

PWM flow - nodes linking the websockets input to dashboard widgets

The entire websockets data payload is converted to JSON* string format, ( "{"name":"value" }" pairs ) and then output to the debug sidebar on the right. Basically, the other nodes separate out specific measurements from the string, ( battery voltage, battery charge state, time-stamp, moisture value, moisture level & version information ), which are then sent to the relevant widgets on the custom dashboard for viewing.

PWM dashboard displaying real-time data

Another flow & dashboard was also created consisting of just the battery voltage charge/discharge chart 📉widget and left running for 22 hours for the purpose of establishing the discharge characteristic of the 3.7V 1000mAh rechargeable Lithium-Ion-Polymer battery which powers the PWM.

3.7V 1000mAh Li-Po battery discharge characteristic

The value displayed on the primary dashboard for the 'percentage charge remaining' is based on the profile of that chart.🔲

* JSON = Java Script Object Notation.

Plant Water Monitor - PWM

🔘The "Plant Water Monitor" ( PWM ) project has been completed. It's function is to measure the 💧moisture in the soil where a 🪴plant is growing. The PWM consists of a capacitive soil moisture sensor, µ-controller, rechargeable battery, 🔋battery charger, waterproof enclosure, 🛜Wifi and webserver serving a webpage. In use, the protruding moisture sensor is pushed into the soil near the 🪴plant's roots.

Plant Water Monitor

The ﹌moisture measurement is sent by the webserver using 🛜Wifi and 'Websockets' to the PWM webpage opened in a browser, running on a client computer💻 or phone🖁. Websockets and the preliminary webpage designs were the subjects of the last post, on 📅20 April 2025. 

Two PWM firmware versions have been made; each having a different 🛜Wifi configuration. Depending on the location of the 🪴plant of interest, either the version of the PWM configured as a 🛜Wifi 'Station (STA)' on an existing network or the version configured as a stand-alone 'Soft Access Point (SAP)' would be chosen. The former requires an existing 🛜Wifi network to be in range of both the PWM and phone etc; the latter does not have that restriction but does require the client device to be connected to SSID "SpacerLabs-Wifi-Sensors".

A different webpage has been designed for each version of the PWM, using HTML, CSS & JavaScript. The webpage ( IP:192.168.1.63 ) for the version supporting 'STA' is almost identical to V4 shown in the previous post, with the addition of the 🔋battery charge status.

Notice the 'favicon' in the browser page tab (click to enlarge)

The webpage for the PWM version supporting 'SAP' is shown in the image below, and is being displayed on a phone's browser, after connecting to 🛜Wifi network 'SpacerLabs-Wifi-Sensors' & then navigating to IP:192.168.4.1.

Page: plant-water-monitor-v2.html

Features supported include Wifi signal monitoring, 🕓time-stamp, battery🔋 charge state, soil moisture, serial number, chip model & revision, pop-ups for 💦moisture level categories and ⛿flagging recommended action.

The latest issue of the 'User Guide' can be downloaded 🔗 here 🔘

Websockets Servers & Websockets Protocol

🔳A couple of our recent projects involving sensors & WiFi, ( 'Solarometer' 📅13.10.2024 & 'Greenhouse Gas Sensors'  📅01.12.2024 ), have an integrated webserver hosting a webpage so that the sensor readings can be displayed on a client device, e.g., phone 🖁or computer💻, running a browser. Either HTTP or AJAX protocol was employed for the server-client connection.

A🪴'Plant Water Monitor'  is a new project which will use a Websockets Server & Protocol instead. Websockets was briefly mentioned in the 'Solarometer' post. To recap, unlike HTTP or AJAX, Websockets provides real-time server/client communication over a continuously open full-duplex bidirectional connection 🔁, requiring no page refreshes or other requests; just the measurement data ( not the entire page ), are sent automatically, with minimal latency.

Testing Websockets has been successful. The Websockets server, ( programmed on the µ-controller in the 🪴Plant Water Monitor ), is assigned IP address 192.168.1.51 when it establishes a connection with our Wifi network router access point. Navigating to that address with a browser on a 🖁phone or 💻computer displays the page to see the data being updated.

Several variations of a webpage were designed, ( again using HTML, CSS & JavaScript ). One or more will eventually be selected as a basis for the design for the 🪴Plant Water Monitor. Each has the filename soil-moisture-sensor-vn.html. Websockets protocol is used to automatically update ( ⏱every hour or every minute ) the moisture﹌ readings, time stamp of the last reading, and Wifi signal level, in real time.⌚

V1 viewed on a phone

V1 is the basic page design having the essential features. Wifi signal level ( at the moisture sensors location ), moisture ﹌readings at two locations and time-stamp are updated automatically without any intervention required from the user.

V2 + WiFi signal level meter

V2 as V1, with the addition of an analogue bar-meter showing the WiFi signal level changing to assist in choosing a location for the remote sensor. 

V3 + popup notification

V3 as V1, with the addition of an alarm ⏰ condition pop-up advising that action should be taken on the basis of the reported moisture measurement. 🥀🏜

V4 + button & background image

V4 as V1, with the addition of a 'button' which when tapped will show or hide the moisture level descriptions, and with the addition of a background image of the 🪴'Plant Water Monitor' itself.

Note that the ⌂"home" icon in V2, V3 & V4 is continuously spinning.

🔲