[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.
We’ve seen an incredible number of homebrew environmental monitors here at Hackaday, and on the whole, they tend to follow a pretty predicable pattern. An ESP8266 gets paired with a common temperature and humidity sensor, perhaps a custom PCB gets invited to the party, and the end result are some values getting pushed out via MQTT. It’s a great weekend project to get your feet wet, but not exactly groundbreaking in 2022.
Which is why we find the AERQ project from [Mircea-Iuliu Micle] so refreshing. Not only does this gadget pick up temperature and humidity as you’d expect, but its Bosch BME688 sensor can also sniff out volatile organic compounds (VOCs) and gases such as carbon monoxide and hydrogen. The datasheet actually claims this is the “first gas sensor with Artificial Intelligence (AI)”, and while we’re not sure what exactly that means in this context, it’s a claim that apparently warrants a price tag of $15+ USD a pop in single quantities.
But the fancy sensor isn’t the only thing that sets AERQ apart from the competition. Instead of a member of the ubiquitous ESP family, it’s using the Wio-E5, a relatively exotic STM32 package that integrates a long-range LoRa radio. [Mircea-Iuliu] has paired that with a Linx USP-410 chip antenna or, depending on which version of the four-layer PCB you want to use, a u.Fl connector for an external antenna. The whole thing is powered by a simple USB connection, and its Mbed OS firmware is setup to dump all of its collected data onto The Things Network.
All told, it’s a very professional build that certainly wouldn’t look out of place if it was nestled into some off-the-shelf air quality monitor. While the high-end detection capabilities might be a bit overkill for home use, [Mircea-Iuliu Micle] points out that AERQ might provide useful insight for those running indoor events as COVID-19 transitions into its endemic stage.
As more of the world’s communication moves into the electronic realm, a casualty has come in the physical mail. Where once each new day might have brought with it a bulging mailbox, today it’s not uncommon for days to pass with not even so much as a bill or a coupon book. For [Eivholt] this presents a problem: he doesn’t want to miss a parcel but most visits to the mailbox are futile. His solution is a LoRa-connected mailbox monitor that sips power from a pair of AAA batteries to the extent that so far it’s run for over two years on a single set.
At its heart is a single board, a Talk2 Whisper Node. This packs a low-power version of the ATmega328 microcontroller alongside a LoRa radio and an efficient power regulator allowing it to draw only 8.70 uA in standby mode, waking up only for extremely short periods to check for mail and report via LoRa to The Things Network. The sensor is simply a microswitch, selected after finding a reed switch problematic to install. Finally an SDR was used to debug the operation of the radio.
The write-up also provides an introduction to extreme low power projects, including some tips on measuring such tiny currents. Even if you have no interest in a mailbox, any tricks that can help maximize power efficiency are always worth taking a look at. Check out the video after the break to see this radio-equipped mailbox in action.
LoRa is the new hotness in low-power, long-range communications. Wanting to let the packets fly, [Xose] was faced with a frequecny problem and ended up developing a Europe-friendly LoRa module for the M5Stack system. The hardware is aimed at getting onto The Things Network, a LoRa based network that provides connectivity for IoT devices. While there was an existing M5Stack module for LoRa, it only supported 433 MHz. Since [Xose] is in Europe, an 868 MHz or 915 MHz radio was needed. To solve this, a custom board was built to connect the HopeRF RFM69 series of modules to the M5Stack.
If you haven’t heard of it before, the M5Stack platform is a stackable development board platform. Like Arduino, you can add functionality by stacking PCBs using a standard header. Unlike Arduino, M5Stack fits in a case nicely and is designed for building devices with user interfaces. For $35, you get an ESP32 based system with WiFi, Bluetooth, a color LCD, battery, buttons, a speaker, and IO connectors.
With the hardware in place, [Xose] 3D printed a custom case to hold the board and added it to the stack. The firmware acts as a monitor for The Things Network, showing live coverage. The final product looks very clean for a prototype, maintaining the finished look of M5Stack.
The firmware, board design, and case design files for the project are all available on Github.