OWB Monitor
A hydronic woodboiler monitoring node built on the LILYGO T-SIM7080-S3 and four DS18B20 temperature sensors. Monitors supply and return temperatures on two loops, pump current draw on each loop, and sends alerts via Telegram and Home Assistant.
Hardware
- LILYGO T-SIM7080-S3 (ESP32-S3 + SIM7080G cellular)
- DS18B20 waterproof temperature probes x 4
- SCT-013-030 current transformer clamps x 2
- ADS1115 16-bit ADC
The board, ADS1115, and wiring all fit inside a standard IP65 enclosure. Sensor cables enter through PG7 and PG9 cable glands.
System diagram
Four DS18B20 sensors on the 1-Wire bus measure supply and return temperatures on both hydronic loops. Two SCT-013-030 CT clamps feed the ADS1115 ADC for pump current. The ESP32-S3 publishes over MQTT/TLS to the broker, with LTE-M cellular as fallback. Alerts go through Home Assistant automations and direct Telegram Bot API.
What it measures
- Supply and return temperature - house loop
- Supply and return temperature - barn loop
- AC current draw - house loop pump
- AC current draw - barn loop pump
Collection interval: 60s (temperature), 60s (current)
Enclosure
The node sits in an IP65 junction box mounted near the boiler. The LTE antenna is stuck to the inside of the enclosure wall for cellular fallback when WiFi is unavailable.
Cable glands (PG7 for temperature sensor wires, PG9 for current clamps) keep the enclosure sealed while allowing cable entry.
Alerts
- Supply temperature below 55C - boiler going out or not heating
- Supply/return delta below 5C - possible flow or pump issue
- Pump current close to zero during heating hours - pump failure