The first version was an ESP32-C3 and a temperature / humidity sensor joined by jumper leads. Small enough to get a reading, with everything still out in the open.
1 / 5
02 / One board
Making room for CO₂
The controller, CO₂ sensor and temperature / humidity board came together on a soldered carrier. A blue printed shell was the first attempt at giving the electronics a home.
2 / 5
03 / Round display
A reading you can see on the device
The round screen sits above the electronics. Headers, short jumpers and the display tab make the stack much tighter than the first wired prototype.
3 / 5
04 / Print & fit
Working through the enclosure
Different lids, display seats and case walls were printed and tried against the real board. These blue and yellow parts show the fit changing along the way.
4 / 5
05 / White enclosure
The current build
The same compact stack, inside a rounded white enclosure. The circular display brings CO₂, temperature and humidity together on the front.
A homemade room sensor, a view of the house, and a radiator that reports back when its setting changes.
Notes updated
The white enclosure with the display running.
From the circuit board to the room view
A reading has somewhere to go.
The sensor is only one end of the project. AWS carries its readings into my dashboard — and carries settings back to the device.
On the device◎
MTS-3
Read the sensors
ESP32-C3 · SHTC3 · SCD40
AWS / connect↔
IoT Core
Receive pointset
MQTT · mutual TLS
AWS / processλ
Telemetry Lambda
Validate the message
Identity · points · values
AWS / retain▤
DynamoDB
Store the reading
Timestamped records
AWS / serve⌁
HTTP API
Query latest + history
API Gateway · Lambda · Cognito
In the browser▥
My dashboard
Put it in the room view
React · hosted on Amplify
DEVICE → CLOUD → DASHBOARD
Each pointset message is checked and stored. The signed-in dashboard requests the latest values and history through the HTTP API.
Illustrative messages and timing. This graphic does not connect to the private dashboard or send commands to devices.
DBO / what a point means
A name that survives the journey.
Digital Buildings Ontology names describe the measurement, rather than the pin it arrived on. The device registry pairs each point with its units and allowed values, so the firmware, cloud and dashboard share the same meaning.
zone_air_temperature_sensor
Temperature · degrees_celsius
zone_air_relative_humidity_sensor
Humidity · percent_relative_humidity
zone_air_co2_concentration_sensor
CO₂ · parts_per_million
UDMI / how it is carried
Readings, settings, and a reply.
The implemented UDMI 1.5.2 message shapes separate measured pointset values, desired config, and reported state. It is a focused UDMI-style implementation, not the full UDMI toolchain.
Inside the pointset message Example JSON{site}/MTS-3/events/pointset
DEVICE INTELLIGENCEEXAMPLE VIEW
Air-sensor node MTS-3
Temperature23.4 °C
Humidity46 %
CO₂768 ppm
CO₂ history 24H
Reporting 5mPOINTSET · STATE · CONFIG
Where the messages become useful
The dashboard closes the loop.
The private sensor view brings together temperature, humidity and CO₂, selectable history ranges, reporting intervals and a message inspector. The wider room view puts those readings back into the house.
A setting is only shown as applied after a matching device-state acknowledgement. Publishing a configuration to AWS is one step; the device confirming it is another.
Hardware and software at a glance
Devices
ESP32-C3 nodes, one per room
Sensors
SHTC3 (T, RH) · SCD40 (CO₂)
Cloud
AWS IoT + serverless services
Interface
React view of both floors
Control
Terma radiator over BLE
PlatformA small building system
This started as a way of seeing temperature and humidity around a house. It grew into
a private building view where each room can show its sensor readings, history, device
state, and, where it makes sense, controls.
ESP32-C3 devices publish structured messages through AWS IoT. Serverless services
validate and store the readings, while a React dashboard puts them back onto the two
floors of the house. The same path carries configuration in the other direction.
ESP32-C3
MQTT
AWS IoT Core
Lambda
React
Bluetooth LE
Each physical device has its own identity and certificate.
Readings keep their device, room, timestamp, and units attached.
The interface distinguishes a requested change from one the device has actually applied.
HardwareThe air-sensor node
The first version paired an ESP32-C3 with an SHTC3 for temperature and humidity. I later
added an SCD40 CO₂ sensor on the same I²C bus and carried the new reading through the
firmware, device metadata, cloud services, history charts, and room view.
The deployed device reports temperature, humidity, and CO₂ using the point names and
units expected by the rest of the platform. The board is still deliberately homemade:
protoboard, short wiring runs, and a printed enclosure that can be opened again.
The wired prototype that came first.The compact temperature and humidity node.
From the bench · September 2026
The white enclosure is the current setup. Blue prints record the earlier fit checks and blower experiments.
Inside the white enclosure: display, sensors and USB-C.The assembled electronics before fitting the case.Side view of the display and board stack.The soldered wiring underneath the perfboard.Printed enclosure iterations and the sensor board.Side view of the blower fit trial.
More build photosLids, soldering and blower trials
Blue enclosure: checking the side clearance.Blue lid and round display, before power-up.Blower depth beside a ruler.Blower bench wiring with a separate ESP32-C3.Blower and test connections.The white build during blower testing.Blower fit trial in the blue enclosure.An earlier blue display lid.The GC9A01 display seated in the lid.Soldering the perfboard connections.Display and sensors assembled on perfboard.Blue base, sensor board and clip-on lid.Blower footprint beside a ruler.USB power and blower test wiring.Earlier lid, retaining ring and enclosure prints.
EnclosureBuilt around the real board
I measured the assembled board before drawing the enclosure, then printed and adjusted
the shell until the sensor openings, lid, and USB-C access all worked with the hardware
that was actually on the bench.
The two-part enclosure before printing.The printed shell with the CO₂ board it was made for.
A case with a round display
The current build has a white printed enclosure and a 1.28-inch round display showing
CO₂, temperature and humidity. The screen sits above the hand-soldered perfboard,
with USB-C power entering on the right. The model at the top follows this setup from the
September photos; its dimensions are approximate. The enclosure page
keeps the earlier Slab, Gauge and Halo studies alongside the current build.
HeatingThe radiator bridge
A separate ESP32-C3 acts as a Bluetooth bridge for a Terma MOA Blue electric radiator.
I used a small probe program to work out how the real controls behaved, then turned that
into a bridge between cloud configuration and the radiator’s BLE characteristics.
Requested temperatures are range-checked, written to the radiator, read back, and then
reported to the platform. The web interface waits for that device response before it
calls a change applied. One radiator has been tested through that complete path; adding
another is still future work.
Current stateStill a working project
The sensor, cloud, dashboard, and first radiator-control paths have all been used on the
real system. I’m still changing the hardware packaging and the operational side of it,
so this page is a record of where the project is now rather than a finished-product claim.
