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John Pinner - Clockwork Software Systems

Linux at Home

A long time ago, I installed central heating in our home, a wet system with gas-fired boiler and a (then) state-of-the-art control system. Recently I replaced the boiler, but was disappointed to find that there was no modern equivalent to the old control system.

It didn't take long to realise that it shouldn't be impossible to create a new and improved controller using PC technology. All we needed were a few relays to switch things on and off, some temperature sensors to measure what was going on, and some software to glue it all together.

So was born a Python-based project to control our heating system with the objective of maximising comfort and minimising running costs. It has been both fun and satisfying putting it into practice.

The presentation will describe the control system and its development.

Presentation Outline

• Objectives: Matching heating to requirements for best comfort and economy.
• Design decisions: Two control loops, balancing heat loss through building fabric rather than controlling room temperature directly. Assigning priority between room and domestic hot water heating.
• Hardware : Standard PC hardware with battery backup; interfaces to control mains electricity and measure several temperatures.
• Python software : Controlling boiler, pump and motorised valves; using fuzzy logic for the inner control loop; measuring temperature values and rates of change;saving the data and making the system learn from it. Providing a human interface.
• Achievement of objectives : shortcomings and future plans. Would I do it again?