Monitoring Your Central Heating Boiler Using a Raspberry Pi – Hardware, Software, and Setup Guide

Hardware Overview

Below is a concise list of the Raspberry Pi components required for this boiler monitoring system. The relay unit, which manages the boiler’s burner and pump, remains unchanged from the original PC setup.

• Raspberry Pi Model B
• Pi‑Face Digital interface card
• Dallas Semiconductor (Maxim) DS9490R 1‑Wire USB adapter
• Dallas Semiconductor (Maxim) DS18S20 1‑Wire temperature sensors

The block diagram (not shown) illustrates the general wiring layout. Optionally, a GSM modem can be integrated later to receive SMS alerts.

Software Components

Three primary programs drive the monitoring system:

• Event logger – talks to the Pi‑Face Digital card and records the status of mains power, pump operation, and burner firing. Data are written to a daily log file.
• Temperature logger – reads the 1‑Wire sensor network and logs temperature readings from each sensor to a separate daily file.
• CGI renderer – invoked by Apache, it generates a calendar view and renders SVG graphs of events and temperatures.

All programs were originally written in C for a Windows/2000 Server environment on a Dell GX11 PC. The transition to Linux required significant rewrites, especially for the Pi‑Face Digital API and the OWFS (One‑Wire File System) interface.

The CGI module is the most complex part; it produces an SVG bar chart and timeline. It was ported to Linux by replacing _stat() calls with statfs() and correcting string handling routines.

Filesystem Layout

Typical Linux and Apache directories are highlighted in yellow; custom paths appear in blue. All monitoring files live under /1-wire:

/1-wire
├─ src
├─ events
├─ temperatures

Step 1 – Create Directories

sudo su
cd /
mkdir /1-wire
mkdir /1-wire/src
mkdir /1-wire/events
mkdir /1-wire/temperatures

Step 2 – Download and Compile

wget https://www.noveldevices.co.uk/rpdl/logger.c -O /1-wire/src/logger.c
wget https://www.noveldevices.co.uk/rpdl/1-wire.c -O /1-wire/src/1-wire.c
wget https://www.noveldevices.co.uk/rpdl/server.c -O /1-wire/src/server.c

gcc -L/usr/local/lib -lpiface-1.0 -o /1-wire/events/logger /1-wire/src/logger.c -lm
gcc -L/usr/local/lib -o /1-wire/temperatures/1-wire /1-wire/src/1-wire.c -lm
gcc -L/usr/local/lib -o /usr/lib/cgi-bin/server /1-wire/src/server.c -lm

Step 3 – Fetch Configuration and Stylesheet

wget https://www.noveldevices.co.uk/rpdl/1-wire.conf -O /1-wire/temperatures/1-wire.conf
wget https://www.noveldevices.co.uk/rpdl/server.conf -O /usr/lib/cgi-bin/server.conf
wget https://www.noveldevices.co.uk/rpdl/boiler.css -O /var/www/boiler.css

Step 4 – Configure 1‑Wire Logging

The 1-wire.conf file contains settings for the logger and the CGI graph generator. Each entry is independent of order:

• [Interval]=n – polling interval in seconds (adjusted to avoid drift; OWFS usually needs ~2 s per sensor).
• [DataDirectory]=/path/to/data/ – directory where log files will be stored.
• For each sensor: [DevicePath]=/path/to/owfs/ #RRGGBB sensor‑description

Here, #RRGGBB is the HTML colour code for the sensor’s line on the graph, and sensor‑description is the label displayed on the temperature plot.

For additional details, refer to the original article: Monitoring My Central Heating Boiler.