[Aduecho] had seen those cheap eBay deals of e-paper-based pricing tags, and was wondering if they could be hacked to perform some other tasks. After splitting the case open, the controller chip was discovered to be a SEM9110, with some NFC hardware support but little else. [aduecho] was hoping to build some IoT-connected air quality indicator (AQI) units but the lack of a datasheet for SEM9110 plus no sensors in place meant the only real course of action was to junk the PCB and just keep the E-paper display and the batteries. These units appeared to be ‘new old’ stock, so there was a good chance that both would be fresh and ripe for picking.
The PCB [aduecho] came up with is mechanically the same as the original unit, but now sports a Seeed studio Wio-E5 LoRa module, which uses the STM32WLE5 from ST for the heavy lifting. This has what looks like a Semtech SX126x integrated on-die (we can’t think of a sane way an actual SX126x die could be flip-chip mounted, but you never know). Using this module is a snap, needing only very minimal antenna-matching components and a spot of decoupling to function. On the sensing side of things, a Bosch BME680 gas sensor handling the AQI measurements, and a Bosch BMI270 6-axis IMU, provides a gyro and accelerometer, for all those planned user interaction features. As can be seen from the schematic, interfacing the EPD is pretty straightforward, just a handful of parts are needed to generate the necessary bipolar gate voltages via a simple SMPS circuit. The display controller handles it all internally, programmed via an SPI interface.
One area we’re quite fond of in this project are the neat hand-drawn icons, and variable width font, giving the display a kind of note-like quality when drawn on the low-ish contrast e-paper display.
When [tdw] wasn’t feeling well one day, his wife suggested that it might be due to poor air quality in their home. While an ordinary person could have simply opened a window after hearing such an idea, [tdw] instead showed his true hacker spirit and set about measuring the indoor air quality. He began by designing a simple PCB to measure CO2 and volatile organic compound (VOC) levels, but eventually broadened his scope to end up with the Sensor Playground: a plug-and-play platform to read out various sensors and store the results in the cloud.
Deliberately designed to be easy to assemble with minimal soldering skills, the Sensor Playground consists of a big two-layer PCB onto which various modules can be plugged. It supports either an ESP32 DevKit or an Adafruit Feather module to provide processing power, and provides sockets for a bunch of sensors, conveniently wired with power and SPI or I2C. It also provides a rotary encoder and two buttons for user input. All source files are available on [tdw]’s GitHub page, ready to be applied to any kind of sensing task.
[tdw] set up his Sensor Playground with sensors measuring CO2, VOC, PM2.5 (particulate matter), as well as temperature and relative humidity. A web interface allows anyone to track these measurements in real-time. The open and modular design should make it easy to extend this system with various other sensor types: we can imagine that things like solar irradiation, outside temperature and wind speed would also add useful data to the mix. Perhaps even a Geiger counter to keep track of radiation levels?
[Andrew Lamchenko], who has built a number of small e-ink-based sensors this year, released another design called the eON Indoor Air Quality Sensor. As his previous sensor designs, the eON boasts a striking appearance with all the spit and polish of a commercially made product. Except [Andrew]’s design is completely open-source.
Besides showing air quality, it also shows basic weather conditions, and there’s a built-in weather forecasting algorithm as well. It can operate standalone or use the radio module to send readings to a smart home system.
The core sensor is the SGP40, which detects volatile organic compounds (VOCs) in the air while consuming less than 3 mA (compared to the 48 mA of the previous generation). There’s a temperature, barometric pressure, humidity, and light sensors in the package as well. Like many projects these days, [Andrew] encountered parts supply issues along the way. Because of that, and to make the design more flexible, several versions of the board have been made to accommodate the different permutations of:
2.13-inch e-ink display
DES e-ink display, coming soon
Radio, four flavors
MINEW MS88SF3 (nRF52833, nRF52840)
MINEW MS50SFA1 (nRF52810, nRF52811)
MINEW MS50SFA2 (nRF52832)
EBYTE E73-2G4M08S1C (nRF52833, nRF52840)
Temp / Pressure sensor:
[Andrew] not only designed the sensor but has done a thorough job on the documentation. Check out the GitHub repository of the project for a complete data package covering all aspects of the design, including the weather forecasting app note by John Young (an NXP engineer, not the astronaut). Last week the design was named as a finalist of the 2021 Hackaday Prize. We’re excited to see where he goes with this between now and the end of October!
Do you use an air quality sensor in your home? If so, is it only for informational purposes or do you take action based on the data, such as automatically turning on a fan or escaping to the countryside? Let us know in the comments below.
Over the years many people have made an air quality monitor station, usually of some configuration which measures particulates (PM2.5 & PM10). Some will also measure ozone (O3), but very few will meet the requirements that will allow one to calculate the Air Quality Index (AQI) as used by the EPA and other organizations. [Ryan Kinnett]’s project is one of those AQI-capable stations.
The AQI requires the measurement of the aforementioned PM2.5 (µg/m3), PM10 (µg/m3) and O3 (ppb), but also CO (ppm), SO2 (ppb) and NO2 (ppb), all of which has to be done with specific sensitivities and tolerances. This means getting sensitive enough sensors that are also calibrated. [Ryan] found a company called Spec Sensors who sell sensors which are pretty much perfect for this goal.
Using Spec Sensor’s Ultra-Low Power Sensor Modules (ULPSM) for ozone, nitrogen-dioxide, carbon monoxide and sulfur dioxide, a BME280 for air temperature, pressure and relative humidity, as well as a Plantower PMS5003 laser particle counter and an ADS1115 ADC, a package was created that fit nicely alongside an ESP8266-based NodeMCU board, making for a convenient way to read out these sensors. The total one-off BOM cost is about $250.
The resulting data can be read out and the AQI calculated from them, giving the desired results. Originally [Ryan] had planned to take this sensor package along for a ride around Los Angeles, to get more AQI data than the EPA currently provides, but with the time it takes for the sensors to stabilize and average readings (1 hour) it would take a very long time to get the readings across a large area.
Ideally many of such nodes should be installed in the area, but this would be fairly costly, which raises for [Ryan] the question of how one could take this to the level of the Air Quality Citizen Science project in the LA area. Please leave your thoughts and any tips in the comments.
[Radu Motisan]’s entry in the 2017 Hackaday Prize is a series of IoT Air Quality monitors, the City Air Quality project. According to [Radu], air pollution is the single largest environmental cause of premature death in urban Europe and transport is the main source. [Radu] has created a unit that can be deployed throughout a city and has sensors on it to report on the air quality.
The hardware has a laser light scattering sensor for particulate matter and 4 electromechanical sensors for carbon monoxide, nitrogen dioxide, sulfur dioxide and ozone (these sense the six parameters that are recognized as having significant health impact by multiple countries.) These sensors have2-yearear lifespan, so they are installed in sockets for easy replacement, and if needed, you can swap to different sensors to detect different things. The PCBs for the hardware are separated into a WiFi version and a LoRaWAN version and the software runs on an ATMega328 – the PCB has the standard six-pin ISP connection for programming.
The data collected is sent to a server where it is adjusted based on the unit’s calibration parameters and stored in a database per sensor. This makes servicing the sensors at the end of their life easier as all that’s required is replacing the sensors in the unit and changing the calibration parameters stored for that unit, the software changes are required. The server offers the data via a RESTful API so that building dashboards with the stats and charts become easy.
[Radu] used an off the shelf module as the first prototype and attached it to a car while driving around. He used this to test out the plan and work on the server. He then proceeded to designing the PCB hardware and the enclosure for the final unit. This work is an extension of [Radu]’s previous work, spotlit here in the 2015 Hackaday Prize, but also check out this project to put air quality sensors in the classroom.
Handheld measuring devices make great DIY projects. One can learn a lot about a sensor or sensor technology by just strapping it onto a spare development board together with an LCD for displaying the sensor output. [Richard’s] DIY air quality meter and emissions tester is such a project, except with the custom laser-cut enclosure and the large graphic LCD, his meter appears already quite professional.
Ever consider monitoring the air quality of your home? With the cost of sensors coming way down, it’s becoming easier and easier to build devices to monitor pretty much anything and everything. [AirBoxLab] just released open-source designs of an all-in-one indoor air quality monitor, and it looks pretty fantastic.
Capable of monitoring Volatile Organic Compounds (VOCs), basic particulate matter, carbon dioxide, temperature and humidity, it takes care of the basic metrics to measure the air quality of a room.
All of the files you’ll need are shared freely on their GitHub, including their CAD — but what’s really awesome is reading back through their blog on the design and manufacturing process as they took this from an idea to a full fledged open-source device.
Did we mention you can add your own sensors quite easily? Extra ports for both I2C and analog sensors are available, making it a rather attractive expandable home sensor hub.
To keep the costs down on their kits, [AirBoxLab] relied heavily on laser cutting as a form of rapid manufacturing without the need for expensive tooling. The team also used some 3D printed parts. Looking at the finished device, we have to say, we’re impressed. It would look at home next to a Nest or Amazon Echo. Alternatively if you want to mess around with individual sensors and a Raspberry Pi by yourself, you could always make one of these instead.