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SILICON CHIP Mini Projects #016 – by Tim Blythman WiFi Weather Logger This simple but incredibly useful project can put the weather at your fingertips. It monitors and logs temperature and humidity. You can download the logs and see all the important statistics from a web browser on any device connected to your WiFi network. Y ou can buy all manner of wireless weather stations but this one is simple and easy to build. Because it’s programmed using the Arduino IDE, you can customise it as you wish. The hardware assembly is simple as it consists of just three pluggable boards. You might need to do some soldering if the headers are not already attached when you buy them, but that’s about it. We’re using a WiFi Mini board, which sports an ESP8266 processor. A module based on the DHT11 sensor measures the temperature and humidity. Finally, a microSD card module is used to save the data. Fig.1 shows the circuit for the Logger, with the three boxes showing the contents of each of the peripheral modules. The WiFi Mini board has a few niceties that aren’t shown, such as a USB-serial converter and voltage regulator, while the other modules are quite minimal. The processor on the WiFi Mini board connects to the DHT11 sensor using its D4 digital input/output pin. It uses a simple bidirectional one-wire protocol, so only one pin is needed, along with the included 5.1kW pullup resistor. You’ll note that the onboard LED of the WiFi Mini also uses the D4 pin. It doesn’t interfere, and we know communication is occurring when the LED flashes. The SPI pins of the WiFi Mini board connect to their respective pins on the microSD card socket. siliconchip.com.au If you don’t have the exact DHT11 module or microSD card shield, then you should be able to work out the connections using Fig.1. The software library we are using also supports the similar DHT22 sensors without requiring any changes. However, note that we have not tested this. Construction Ensure that the three boards are fitted with suitable headers. We used stackable headers on all of them for flexibility, but you could use male or female headers for some to make the stack more compact. Simply plug the boards together, being sure to match their orientation to our photos! We placed the DHT module at the bottom so it wouldn’t be affected by any heat rising from boards below it. We put the WiFi Mini board at the top to keep it free from radio interference, meaning the microSD card module ended up in the middle. If you don’t have the shields, a breadboard or prototyping board might help to make the connections, although you might need a few jumper wires to complete the circuitry. Fit a microSD card to the socket, Fig.1: the circuit consists of three shield boards that we plugged together, although you could use different modules/components and jumper wires if you already have them. The coloured boxes show the contents of the two peripheral boards and how they connect to the processor board. Australia's electronics magazine December 2024  59 freshly FAT-formatted if possible. FAT16 and FAT32 are supported; usually, FAT16 is used for cards up to 2GB. The fewer files on the card, the less processing the WiFi Mini will have to do to read it. The Logger generates less than 1MB of data per year, so even a low-capacity card should be sufficient. Parts List – Weather Logger (JMP016) 1 WiFi Mini ESP8266 Main Board (MOD1) [Jaycar XC3802] 1 microSD card shield (MOD2) [Jaycar XC3852] 1 DHT11 temperature and humidity shield (MOD3) [Jaycar XC3856] 1 FAT-formatted microSD card 1 micro USB cable for programming and power The WiFi Weather Logger uses just these three modules, a microSD card and a micro USB cable. Add http://arduino.esp8266.com/ stable/package_esp8266com_index. json to the Additional Board Manager URLs list, then search for and install “esp8266” from the Board Manager. You’ll also need the DHTNEW library. We’ve included a copy of version 4.3.1 (the one we used) in the software download package at siliconchip. au/Shop/6/512 You can also search for DHTNEW in the Library Manager to install the library named DHTNEW, or download it from https://github.com/RobTillaart/ DHTNEW If you haven’t used the WiFi Mini before, your computer may need drivers. These can be found in the download section of the Jaycar WiFi Mini product page at www.jaycar.com.au/p/ XC3802 Open the WIFI_WEATHER_LOGGER sketch from the software download package. You will have to edit the sketch to include your WiFi name (SSID) and password, which are set by #defines at the very start of the sketch. The NORMAL_OFFSET #define can be altered to set your local timezone offset in minutes. The default of 600 minutes (+10 hours) is correct for Sydney, Melbourne, Hobart and Canberra. You can see these in Screen 1. Select the serial port of the WiFi Mini and choose “D1 R2 & Mini” for the board type, then upload the sketch to the board. When this completes, open the serial monitor at 115,200 baud and check that everything is working as expected, as shown in Screen 2. The WiFi Mini will reboot after 30 seconds if it does not successfully connect to WiFi. Otherwise, it will report its progress in initialising the hardware. Typing ‘~’ followed by Enter in the Serial Monitor will run the card contents listing seen at the bottom of Screen 2. If you have a problem, trying resetting the WiFi Mini with its RESET button. Check that the card is correctly inserted if it is giving an error. Typing ‘s’ followed by Enter in the Serial Monitor will show its status, while Australia's electronics magazine siliconchip.com.au Software The Logger’s software will connect to the internet and fetch the time using NTP (network time protocol). It will then get temperature and humidity data from the DHT11 sensor hourly and log them to the microSD card. It also presents an HTTP server that can be used to check the status and download data using a web browser. You’ll need to install the Arduino IDE (if you don’t already have it, you can download it from siliconchip.au/ link/aatq) and the ESP8266 processor board add-on. The add-on is installed from the Preferences menu of the IDE. Screen 1: make sure to update your WiFi network settings here so that the Logger can connect to your WiFi network. Adjust the time zone offset (in minutes) relative to UTC to suit your location. Connecting to Tim. ................ Connected! IP address: 192.168.xxx.xxx Getting time from NTP sending NTP packet... 48 bytes received. NTP is 0xEA5C1453 Time is 13:17:39 on 06/08/2024 (local time) SD card initialised Root directory found STATUS: IP=192.168.xxx.xxx, Card OK, NTP OK Card listing: 0 System Volume Information [FOLDER] 1 202404.csv 29541 bytes 2 202405.csv 30525 bytes 3 202406.csv 29541 bytes 4 202407.csv 30525 bytes 5 202408.csv 5516 bytes Screen 2: The Arduino Serial Monitor should show something like this if all is working well. The serial port is set to 115,200 baud. 60 Silicon Chip typing a number followed by Enter (as per listing on Screen 2) will show the corresponding file contents. If you see the LED flashing briefly, about once every two seconds, most likely everything is working as expected. If you have the necessary experience, you can modify the Arduino software to collect and log other data. Web interface Note down the IP address from the Screen 2 status report and type that into a web browser’s address bar. This will only be accessible from your local network (eg, devices that are on the same WiFi network). This should show a web page like the one shown in Screen 3. Your values and the files may be different. Check that the time is correct and that you are getting reasonable readings for temperature and humidity. You can refresh the page to get the latest data. The Logger will record data to the microSD card once per hour, on the hour, so let it run for a while to accrue some data. After that, refresh the page and see that you can download the CSV data files by clicking on the links. One file is generated for each month; each will grow to about 30kB. Screen 3: the Logger’s web page shows the current status and lists any files that can be downloaded from the microSD card. CSV files You can open the CSV files in a spreadsheet program like Excel or LibreOffice Calc. The leftmost column is a so-called ‘date serial number’. If you change this column to a date or time format, it will show as such and should match the date and time text in the second column. You can see this in Screen 4, along with the actual temperature and humidity readings, which can now be charted or converted to another data format as needed. Completion You can now install the Logger in its final location. You’ll need power, and you should make sure that the Logger and its wiring are protected from the sun and rain if it is outside. The shelter used to protect meteorological instruments is called a Stevenson screen (instrument shelter). We had no trouble finding versions online that could be 3D-printed. Otherwise, an inverted plastic container should do the trick. SC siliconchip.com.au Screen 4: CSV files from the Logger can be viewed in a spreadsheet program. You can change the format of column A to a suitable date or time format. Australia's electronics magazine December 2024  61