IESH v0.1 — Field-Testing the Classroom Laboratory

From breadboard to box

This began on 20 May 2026 as a Raspberry Pi, a breadboard and jumper wires, and reached a working environmental station in a hand-cut cardboard box with an OLED window. The steps in between: first live readings on 24 May; the move to soldered perfboard and the full sensor harness in early June; the full sensor suite live on the dashboard for the AIT Jury Day demo on 11 June. The build-log gallery has the full sequence, dated.

The sensor stack

DHT22 and BMP280 carry over from v0. New: a DS18B20 soil-temperature probe on 1-Wire, a capacitive soil-moisture sensor, and MQ-7 (CO) and MQ-135 gas sensors, all read through an MCP3208 8-channel ADC. The MQ sensors output 0–5 V but the ADC reference is 3.3 V, so a two-resistor divider halves the signal and the software multiplies it back. Small detail; ruins your data if you forget it.

Calibration

Soil moisture is calibrated against recorded endpoints — raw ADC 4021 in dry air, 1673 fully wet — and reported as a percentage between them. The MQ sensors get a clean-air baseline (R0) recorded per unit with a calibration script and stored with the data, because every MQ unit is its own animal.

The sky camera

A fisheye camera captures the sky every 15 minutes and runs a simple cloud-cover estimate. One camera is shared between scheduled captures and the live stream, so captures pause while someone is watching — groundwork for the all-sky meteor camera this will eventually become.

The classroom part

The station broadcasts its own WiFi hotspot. Any phone or laptop that joins gets the live dashboard and the learning portal: five modules — climate, soil, air quality, data science, environment — with 25+ activities aligned to the national curriculum, their visualisations driven by the station's own sensors. There is no internet anywhere in that loop, which is exactly the point for the schools this is built for.

Provisioning

One command flashes a complete station onto a blank SD card; first boot installs everything unattended in about ten minutes. The data store lives outside the code directory, so re-flashing software never touches collected data.

What's next

Two things remain. First, cloud sync to the open-data API — the local logs are ready; wiring the uploader to the public ingest schema, with offline backfill and per-device credentials, is the work before a station goes to a school. Second, the enclosure: the sensor zones marked on the cardboard box (head, soil/agri, base bay) set the layout for a custom carrier-HAT and power-management PCB in a 3D-printed enclosure, in two variants — a classroom EDU box, and a sealed, pole-mountable SCI box for outdoor sites.