An anemometer outside

DIY Anemometer For Projects Big And Small

When [Fab] needed an anemometer for his latest project, he was stymied by the limited range and relatively high prices of commercial options. Undeterred, his solution was an impressive DIY anemometer that rivals the off-the-shelf alternatives.

AnemoSens was designed from the ground up as a component for the ambitious WinDIY_2 Horizontal Axis Wind Turbine, however it’s just as suitable as part of your standard home weather station. The microcontroller unit uses RS485/Modbus connectivity, ensuring that data from the wind sensor is accessible across a variety of platforms. Serial-stream via USB and an SD cart slot are also available for recording data, the latter being particularly useful for long-term unsupervised monitoring. [Fab] also integrated an ESP32 for recording data over the air.

The MCU also features a location for the venerable BME280, which is a relatively accurate temperature, pressure and humidity sensor often deployed in DIY weather stations. This feels like a nice touch, as it means the anemometer package alone could feasibly serve as a rudimentary weather sensing station, or as a backup for more elaborate environmental monitoring.

The prototype currently uses a Hall effect sensor for measuring the wind speed, while a AS5048B magnetic rotary encoder does a decent job of measuring rotation (wind direction). Some calibration is likely necessary to improve the accuracy of this setup, but it’s a promising start.

[Fab] has already identified some shortcomings with the bearing, but has a plan for future iterations. He might want to check out this spare-parts anemometer that uses a bearing from an old hard drive.

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Open Source Ultrasonic Anemometer

Weather stations are a popular project for experimenting with various environmental sensors, and for wind speed and direction the choice is usually a simple cup anemometer and wind vane. For [Jianjia Ma]’s QingStation, he decided to build another type of wind sensor: An ultrasonic anemometer.

Ultrasonic anemometers have no moving parts but come at the cost of significantly more electronic complexity. They work by measuring the time it takes for an ultrasonic audio pulse to be reflected the receiver across a known distance. Wind direction can be calculated by taking velocity readings from two ultrasonic sensor pairs perpendicular to each other and using a bit of simple trigonometry. For an ultrasonic anemometer to work properly, it requires a carefully designed analog amplifier on the receive side and a lot of signal processing to extract the correct signal from all the noise caused by secondary echoes, multi-pathing, and the environment. The design and experimentation process is well-documented. Since [Jianjia] does not have access to a wind tunnel for testing and calibration, he improvised by mounting the anemometer on his car’s roof and going for a drive. This yielded readings that were proportional to the car’s GPS speed, but a bit higher. This might due to a calculation error, or external factors like wind, or disturbed airflow from the test car or other traffic.

Other sensors include an optical rain sensor, light sensor, lighting sensor, and a BME280 for air pressure, humidity, and temperature. [Jianjia] plans to use the QingStation on an autonomous boat, so he also included an IMU, compass, GPS, and a microphone for environmental sounds. The fact that none of the sensors have moving parts is a major advantage for this use case, and we look forward to seeing the boat project. All the hardware and software are open-source and available on GitHub.

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An Electronic Love Letter To The Wind

Home weather stations are a great way for hackers and makers to put their skills to practical use. After all, who wants to hear the current conditions for the whole city when they could setup their own station which drills that information down to their very own street? Such a setup doesn’t need to be any more complex than a temperature sensor wired up to a microcontroller, but then not all of us are quite the weather fanatic that [Richard] clearly is.

The system he’s built to monitor the wind over his home is, to put it mildly, incredible. We might not all share the obsession [Richard] apparently has with the wind, but we can certainly respect the thought and design that went into this comprehensive system. From his scratch built anemometer to the various ways he’s come up with to display the collected environmental data throughout his home, if this build doesn’t inspire you to hack together your own weather station then nothing will.

At the heart of the system is the anemometer itself, which makes use of several scavenged parts such as the bottom halves of plastic Easter eggs as wind cups. The cups spin on a short length of M5 threaded rod inside of a 635ZZ bearing, which ultimately rotates a “light chopper” placed between a red LED and a OPL550A optical sensor. In a particularly nice touch, [Richard] has even included a few power resistors arranged around the moving parts to use as a heater which keeps the device from freezing up when the temperature drops. The sensor creates eight digital pulses per revolution, and feeds data into the base station though a 30 meter (98 feet) cable.

From there, the base station uses an ESP8266 to upload wind and temperature data to ThingSpeak and Weather Underground to be viewed through their respective web interfaces and applications. The project really could have ended here and still been impressive in its own right, but the station also includes 433 MHz and NRF24L01 transmitters to send the data to the other display devices which [Richard] has designed.

The 433 MHZ display is built into the frame of a lantern, and shows the current time and temperature on an LED readout as well as historical wind and temperature graphs on a 2.2 inch ILI9341 TFT screen which [Richard] has rotated into a portrait layout. There’s a red light on top that blinks whenever a signal is received to show that the system is working, and even a touch sensor which can be used to turn off the TFT screen at a tap if you’re not interested in seeing the full charts.

The other display, which [Richard] calls the “picture frame” utilizes a dizzying array of single LEDs, a handful of digital LED readouts, and even an OLED screen for good measure. They all work together to show the current wind speed as well the averages for the past day in three hour segments. As this display features a real time display of current wind conditions and averages for as short a period of two minutes, it uses the NRF24L01 receiver to get data from the base station at a rate of 3 Hz.

In the past we’ve seen 3D printed weather stations, and of course some pretty simple affairs using little more than an ESP8266 board and some sensors. But few have ever put so much thought into how to present the collected data to the user. If you’re serious about knowing what it’s like outside the confines of your bunker, [Richard] has got some tricks to show you.

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An LED You Can Blow Out, With No Added Sensor

We’d seen it done with buttons, switches, gestures, capacitive touch, and IR remote, but never like this. [electron_plumber] made an LED that can be blown out like a candle, and amazingly it requires no added sensors. The project uses an Arduino to demonstrate turning a tiny LED on and off in response to being blown on, and the only components are the LED and a resistor.

[electron_plumber] used an 0402 LED and thin wires to maximize the temperature responses.
How is this done? [electron_plumber] uses an interesting property of diodes (which are the “D” in LED) to use the LED itself as a temperature sensor. A diode’s voltage drop depends on two things: the current that is being driven through the diode, and the temperature. If the current is held constant, then the forward voltage drop changes reliably in response to temperature. Turning the LED on warms it up and blowing on it cools it off, causing measurable changes in the voltage drop across the device. The change isn’t much — only a handful of millivolts — but the effect is consistent and can be measured. This is a principle [Elliot Williams] recently covered in depth: using diodes as temperature sensors.

It’s a clever demo with a two important details to make it work. The first is the LED itself; [electron_plumber] uses a tiny 0402 LED that is mounted on two wires in order to maximize the temperature change caused by blowing on it. The second is the method for detecting changes of only a few millivolts more reliably. By oversampling the Arduino’s ADC, an effectively higher resolution is obtained without adding any hardware or altering the voltage reference. Instead of reading the ADC once, the code reads the ADC 256 times and sums the readings. By working with the larger number, cumulative changes that would not register reliably on a single read can be captured and acted upon. More details are available from [electron_plumber]’s GitHub repository for LEDs as Sensors.

Embedded below is a video that is as wonderful as it is brief. It demonstrates the project in action, takes a “show, don’t tell” approach, and is no longer than it needs to be.

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The Solid State Weather Station

Building personal weather stations has become easier now than ever before, thanks to all the improvements in sensors, electronics, and prototyping techniques. The availability of cheap networking modules allows us to make sure these IoT devices can transmit their information to public databases, thereby providing local communities with relevant weather data about their immediate surroundings.

[Manolis Nikiforakis] is attempting to build the Weather Pyramid — a completely solid-state, maintenance free, energy and communications autonomous weather sensing device, designed for mass scale deployment. Typically, a weather station has sensors for measuring temperature, pressure, humidity, wind speed and rainfall. While most of these parameters can be measured using solid-state sensors, getting wind speed, wind direction and rainfall numbers usually require some form of electro-mechanical devices.

The construction of such sensors is tricky and non-trivial. When planning to deploy in large numbers, you also need to ensure they are low-cost, easy to install and don’t require frequent maintenance. Eliminating all of these problems could result in more reliable, low-cost weather stations to be built, which can then be installed in large numbers at remote locations.

[Manolis] has some ideas on how he can solve these problems. For wind speed and direction, he plans to obtain readings from the accelerometer, gyroscope, and compass in an inertial sensor (IMU), possibly the MPU-9150. The plan is to track the motion of the IMU sensor as it swings freely from a tether like a pendulum. He has done some paper-napkin calculations and he seems confident that it will provide the desired results when he tests his prototype. Rainfall measurement will be done via capacitive sensing, using either a dedicated sensor such as the MPR121 or the built-in touch capability in the ESP32. The design and arrangement of the electrode tracks will be important to measure the rainfall correctly by sensing the drops. The size, shape and weight distribution of the enclosure where the sensors will be installed is going to be critical too since it will impact the range, resolution, and accuracy of the instrument. [Manolis] is working on several design ideas that he intends to try out before deciding if the whole weather station will be inside the swinging enclosure, or just the sensors.

If you have any feedback to offer before he proceeds further, let him know via the comments below.

A True 3D Printed Weather Station

If the term “3D printed weather station” makes you think of a printed enclosure for off-the-shelf sensors, don’t feel bad. We thought the same thing when we first read the message [Rob Ward] sent in about his latest project. Surely he couldn’t mean that he actually printed all the principal parts of a serious weather station setup, such as the wind vane, anemometer, or rain gauge?

Except, on closer inspection, that’s exactly what he did. Every part of the weather station is designed in OpenSCAD, printed out, and infused with various vitamins to turn them into functional pieces of hardware. Interestingly enough, most of the magic is done with simple reed switches and magnets.

For example, the wind vane uses eight reed switches and an embedded magnet to communicate the current wind direction to the Arduino Uno which handles the user interface. Wind speed, on the other hand, it done with a single reed switch as it just needs to count rotations to calculate speed.

[Rob] did “cheat” by using an off-the-shelf barometric pressure sensor, but we’ll give him a pass for that one. Unless somebody wants to hit the tip line with a design for a printable barometer, we’ll consider this the high water mark in printable weather stations.

This isn’t the first time we’ve seen a DIY anemometer or rain gauge, of varying degrees of complexity. But the clean look of the final version, completely open nature of the OpenSCAD source, and the low part count make this an extremely compelling option for anyone looking to up their home forecasting game.

Custom Cut Pinwheel Makes A Useful HVAC Duct Flow Meter

Everyone is familiar with pinwheels, and few of us haven’t crafted one from a square of paper, a stick, and a pin. Pinwheels are pretty optimized from a design standpoint, and are so cheap and easy to build that putting a pinwheel to work as an HVAC duct flow meter seems like a great idea.

Great in theory, perhaps, but as [ItMightBeWorse] found out, a homemade pinwheel is far from an ideal anemometer. His experiments in air duct flow measurements, which previously delved into ultrasonic flow measurement, led him to try mechanical means. That calls for some kind of turbine producing a signal proportional to air flow, but a first attempt at using a computer fan with brushless DC motor failed when a gentle airflow couldn’t overcome the drag introduced by the rotor magnets. But a simple pinwheel, custom cut from patterns scaled down from a toy, proved to be just the thing. A reflective optosensor counts revolutions as the turbine spins in an HVAC duct, and with a little calibration the rig produces good results. The limitations are obvious: duct turbulence, flimsy construction, and poor bearings. But for a quick and dirty measurement, it’s not bad.

Looking for an outdoor anemometer rather than an HVAC flow meter? We’ve got one made from an old electric motor, or a crazy-accurate ultrasonic unit.

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