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A professional quality Weather Station based on System designed by A. Caneira* Built and written by Trevor Robinson B ased on the Arduino Nano platform (see right), this lowcost weather station system is very flexible, with many options. To construct this system you will need some basic electronic and computing experience. If you have built and programmed projects using the Arduino platform and associated electronics, then you shouldn’t have any trouble building this one! Part 1 It can use quite a few different sensor types, though in an attempt to simplify the project somewhat, we’ll be sticking to only a few. The Arduino Nano is a small microprocessor board based on the ATmega328 chip that comes preprogrammed with a special bootloader which in turn allows easier end use programming via USB and the There’s a wealth of weather information available – everything from temperature and humidity to rainfall and windspeed. 30  Silicon Chip siliconchip.com.au Main features of 433MHz Existing Fine Offset Sensors WeatherDuino TX Unit 433MHz • It uses affordable parts. USB Internet WeatherDuino RX Unit Windows PC With Cumulus 433MHz WeatherDuino Pro2 Wireless Weather Station System WeatherDuino Pro2 Remote Wireless Display (Optional) Arduino IDE (integrated development environment). It comes with 32KB flash memory though 2KB is used by the bootloader. Its clock speed is 16MHz and its recommended supply voltage is 7-12VDC. Overview This system can be built in a few different configurations using the following modules. TX Unit (Transmitter Unit}. Gathers and processes data from the sensors then transmits this data as packets at different time intervals (for example, wind data is sent every five seconds). Construction and configuration will be covered in Part 2. RX Unit (Receiver Unit). Receives the data from the TX unit and displays the data on either a 20x4 character LCD or 1.8” 160x128 TFT display. You can even run multiple RX units off one weather sensor suite. The RX unit can transmit to the Wireless Display unit (described next). It also displays the temperature and humidity of where it is located. Construction and configuration will be covered in Part 3. WD Unit (Wireless Display Unit). • Uses the commonly available and affordable “Fine Offset” sensors; Anemometer, Wind vane and Rain gauge. The system also allows the sensors to be moved away from each other to better locations. • Has the accuracy of a high-end weather station by utilising DHT/ SHT temperature and humidity sensors. • Can measure and report solar radiation and UV levels with optional board. • Connects to a Windows computer running Cumulus software. This excellent software also allows the unloading of data to your own Weather web site and online services such as WeatherUnderground. Support for cross platform (Windows, Mac, Linux/Raspberry Pi) operating systems is currently in beta testing. • Can run multiple wireless display units that can show the outside data along with the current location temperature. • The outside weather data transmitter (TX Unit) can be run from a solar cell-charged battery. • Communicates over 433MHz with better reliability and data integrity than the donor weather station. • Range can be up to 100m depending on the antenna used and environment. • Can use either an affordable LCD or TFT Display on the receiver unit (RX Unit). • All modules synchronise time from the host computer. A completed Receive Unit (RX unit) in a nice case. The heart of the system is the Arduino Nano shown opposite. siliconchip.com.au * www.meteocercal.info/forum/ March 2015  31 At left is a receiver board fitted to a wall or desk display case. Above (top) is an assembled transmitter (TX) board. This gathers data from each of the sensors and transmits it to the receiver (RX) board, which is shown lower right. This is the latest V4.02 board. Displays received data from the RX unit on either a 20x4 character LCD or 2.4” 320x240 or 1.8” 160x128 TFT display. Wi t h i t s o w n t e m p e r a t u r e / humidity sensor, it too can display the temperature and humidity of where it is located. You can have multiple WDU’s spread around the home or office, as long as they are in range of the RX unit signal. Construction and configuration of this will be covered in Part 4. Solar Radiation Sensor. Interfaces to the TX Unit to supply UV and radiation data. At the time of writing, a standardised setup and procedure is being developed. Currently it’s a bespoke solution due to variations in the solar cells used. For more information on this, it would pay to read up on it at the Meteocercal forum (www.meteocercal.info/forum/). System modules diagram The TX, RX and Wireless display units communicate using 433MHz license-free modules. The TX unit sends the weather data packets to the RX unit, which processes this data and sends it to the PC running Cumulus, via USB using the Davis Pro2/Vue protocol. If you install the few, and optional, extra data relay components, the RX unit actually becomes a transceiver and can relay data to the optional Wireless Display unit. If you wish, you can build and use more than one Wireless Display unit. At the conclusion of this series of articles, you will have a fully-featured weather station. You will also have a Wireless Display Unit that you can put anywhere around the home or office to view the current weather data. If you install the recommended free Cumulus software (please donate to the developer if you do), this weather station’s data will also be able to be viewed on the host computer screen and if desired, uploaded to a website to view anywhere, via Twitter, These graphs show the comparitive accuracy of the Sensirion SHT1x series. To keep the project simple, we are going with the SHT10, which we think is the best mix of value versus accuracy. If you want higher accuracy, you’ll pay more! 32  Silicon Chip siliconchip.com.au WeatherUnderground and a few other on-line services. Choosing a temperature sensor The Sensors Like most things in life, the more you pay, (usually!) the better they are. This is also true for temperature sensors. Here it’s a trade-off of price vs accuracy. Fo r o u t s i d e temperature we usually have a better sensor for this location, one that reads more accurately across the expected temperature and humidity range. We can get away with a cheaper sensor for inside due to the smaller range of temperature and humidity. So do some research and figure out what temperature and pressure sensors you want to go with. Mind you it’s easy to swap these out later if you wanted to upgrade them. To keep the project somewhat simple Now let’s turn our attention to the sensors that connect to the WeatherDuino Pro 2 TX Unit and how they work. The system is designed to use the “Fine Offset” sensor suite. These can found on auction sites etc. Fine Offset weather stations (and their sensors) are often rebadged under a lot of different brand names, ie, Digitech, Holman and a lot more. If the sensors look like those at right then they are very likely to work. LaCrosse sensors should too, though they’re untested at the time of writing. Additionally, the system is also compatible with the RF rain gauges and anemometers from weather stations like Auriol H13726, Ventus W155 and other clones, though these seem to be uncommon in Australia. The Anemometer: This sensor measures wind speed. It is a simple device that uses a reed switch and magnet to measure rotation speed. The Arduino counts the pulses to work out the speed. The Wind Vane: This measures wind direction. It too uses a magnet and reed switches (usually eight or sixteen) to switch in various value resistors, depending on which reed switch the magnet (attached to the vane shaft) is closest to. The Arduino reads the resistance and from this works out where the vane is pointing. The Rain Gauge: Once again, this uses a reed switch and a magnet. The magnet is connected to a mechanism that operates like a seesaw. Once one side gets the amount of water (rain) required (usually measures 0.1mm received in the gauge’s mouth) it tips, moving the magnet past the reed switch and draining the water away. Then it repeats this process filling the other side of the seesaw. The Arduino counts the created pulse(s). Te m p e r a t u r e / H u m i d i t y : T h e recommended sensor for outside temperature / humidity readings is the Sensirion SHT1x (SHT10, SHT11 or SHT15) but the cheaper DHT22 is also supported (not recommended for places with constant high humidity). Barometer: Either the BMP180 or the older BMP085 are supported. The voltage jumper needs to be changed to support one or the other, depending on what pins are used. More on this in Part 3. The optional Solar Sensor: This sensor we are going to assume the SHT10, as we believe it’s the best mix of value versus accuracy. By using multiple TX units, you can mount one or more of the sensors elsewhere. This is handy, for example, if your anemometer needs to be higher t h a n t h e c a bl e allows, or when you need to move the temperature sensor to a better or shadier position. As you will see as we continue through this series of articles, the WeatherDuino Pro2 has the ability to be a complete system in its own right. If you are technically minded and know Arduino programming, you can even add your own extra features as the firmware is open-source and can be modified. is based on a solar cell, that is put to work in its short circuit mode, where its current is proportional to solar radiation. Of course, doing any modifications to the code cannot be supported by the developer or SILICON CHIP magazine. The code is compiled and uploaded to the Arduino Nano microprocessor via a USB connection, using the freelyavailable Arduino IDE (integrated development environment). You will need the Arduino 1.5.8 BETA IDE as the code requires the extra optimisation that this beta release of the IDE gives, otherwise the code will not fit in the Nano’s 32KB flash memory. Data update rates and packet information Wind Data Packet – Sent every 5 seconds. Contains data including Wind Gust, Wind Speed and Wind Direction Wind Speed – Value is a rolling average of the last 5 minutes, sampled every 30 seconds Rain Data Packet – Sent every 31 seconds Temperature/Humidity Data Packet – Sent every 19 seconds Solar Radiation/UV Index Data Packet – Sent every 37 seconds Solar Radiation and UV Index – Values are a rolling average of the last 2.5 minutes, sampled every 37 seconds System Info Data Packet – Sent every 97 seconds. Contains data about system battery or power supply voltage, case temperature (from TMP36 sensor if installed on TX board) and fan state siliconchip.com.au March 2015  33 You can download the Arduino IDE from http://arduino.cc/en/Main/ Software Select and download the Windows Installer option from the above link. We will talk further about the code configuration and how to upload it to the Nano later in part 2 when we need it. KXD-10036 RF This can save you postage costs with some suppliers. Microsoft sent an update that bricked the Nanos with the fake FTDI chip. If you use the recommended CH340G then you will need to download the Windows driver. You can read about this and download the driver (CH341SER.zip) here: w w w. m e t e o c e r c a l . i n f o / f o r u m / Thread-Arduino-Nano-USB-Driver Sourcing the parts Note – Arduino Nano Next month: If this project perks your interest and you’d like to construct it, it may be a good idea to start to organise the collection and purchase of the items required to do so now. We are recommending the Nano that has the CH340G chipset onboard now, as there have been problems with FTDI (fake) chipset drivers since FTDI and In Part 2 of this series, we will get on to construction, specifically, the TX unit – and look at programming the Arduino Nano using the Arduino IDE. DS3231 Real Time Clock module Full parts lists will be presented next month. Many components are over-the-counter items from retailers such as Jaycar Electronics but the table at right lists some of the more “esoteric” components. Most of these were sourced, via ebay, from China. This can result in a delay of 3-4 weeks (or more). This also applies to the PCBs that are only available from the developer in Portugal. To purchase them you will need to sign up at www.meteocercal. info/forum/ and send the developer, Werk_AG, a Private Message to start the process. I’d do this first to get the ball rolling. Where possible, order all of what you need from one supplier at a time. FS1000a Transmitter Module Specifications: • Transmission Distance: 20-200m (higher voltage, longer range) • Idle current: 0mA • Working current: 20-28mA • Working voltage: 3-12V • Transfer rate: 0-10kbps (ideally 2400bps) • Transmit Power: 10-40mW • Transmitting frequency: 433.92MHz • Modulation: OOK (ASK) • Working temperature: -10°C to +70°C 34  Silicon Chip Transmitter/ Receiver Module 433MHz ebay item numbers for hard-to-get or unusual items TX Unit ebay item no.# 1 TX_PCB WeatherDuino Pro2 TX board v4.0x (from MeteoCercal) 1 IRLZ44N 181092926231 (also available in Australia from element14 – order code 8651418) 1 TMP36 (Optional case sensor) 181092361353 1 Arduino Nano v3.0 141287851903 1 FS1000A, 433MHz TX Module 180929057924 1 433MHz antenna 281126334076 1 SMA Female Panel Connector with Pigtail 290916092362 1 SHT10 Digital Temperature And Humidity Sensor Module 271665110416 RX Unit 1 WeatherDuino Pro2 RX board (from MeteoCercal) 1 Arduino Nano V3.0 141287851903 1 DS3231 Real Time Clock Arduino Module 400503978923 1 BMP180 (Recommended!) Barometric Pressure Module 400694164288 (or BMP085 ) 191092156809 1 DHT22 Temperature / Humidity Sensor 170931111400 1 BX-RM06 ASK OOK RF Receiver 200974005470 1 ST7735 1.8” TFT 370695363746 (or 20x4 alphanumeric LCD) 310575296583 (or 16x2 alphanumeric LCD with I2C module) 190847340801 1 433MHz antenna 281126334076 Wireless Display 1 WeatherDuino Pro2 WD board (from MeteoCercal) 1 Arduino Nano V3.0 141287851903 1 DHT22 Temperature / Humidity Sensor 170931111400 1 BX-RM06 ASK OOK RF Receiver Module 433MHz 200974005470 1 1.8” TFT - ST7735 160x128 370695363746 (or 2.2” TFT - ILI9341 320x240) 200953728196 (or 2.4” TFT - ILI9341 320x240) 181500077459 (or 20 x 4 alphanumeric LCD) 310575296583 (or 16 x 2 alphanumeric LCD with I2C module) 190847340801 Optional (required if you want to relay data to a Wireless Display) 1 KXD-10036 RF Transmitter Module 433MHz 200974005470 1 433MHz antenna 281126334076 Miscellaneous 1 SMA Female Board Connector 290646661508 The ebay item numbers shown here may well be sold or no longer available; however if you search for these numbers within ebay an identical device, currently available (and often from the same seller) will usually be shown. Many of the ebay-sourced parts came from the one seller. SC siliconchip.com.au