Lab Notes | Build Log · 15 May 2026

IESH v0 — Build Log and First Data

📍 Kathmandu, Nepal

Full build documentation for the first IESH environmental monitoring station. Component list, wiring, firmware, calibration notes. The DHT22 reads ~2°C high at high humidity — we document the offset and plan to cross-validate with a BME280.

Components

Raspberry Pi 4B, BME280 (pressure/humidity/temperature), SDS011 (PM2.5/PM10), MH-Z19B (CO₂), DHT22 (backup T/RH). Total cost: NPR 12,000.

Assembly

Weatherproof enclosure from a local electronics shop in New Road. All sensors wired via I2C/UART. Python polling script runs every 60 seconds, writes to local SQLite, syncs to himalayansciences.org/api/ingest/ via HTTPS POST.

Calibration Notes

The DHT22 consistently reads ~2°C above the BME280 at humidity >70%. This is a known issue. We use the BME280 as the primary temperature source and log both for cross-validation. First live data appeared on the website within 4 hours of powering up.

What We Learned

The SDS011 PM sensor draws significant current during measurement. On battery backup, duty-cycling the fan (30s on, 270s off) extends runtime without meaningful loss of temporal resolution for hourly averages.