Boiler Control

The laundry node won't just be a passive note-taker, it will also control the boiler.

Our boiler has a basic programmable timer built in, with a limited number of timing slots (which are cumbersome to change). That should be much easier with a tablet based gui, with schedules uploaded to the jeenode. The boiler provides contacts that are in series with the timer switch (by default bridged), meant for an external thermostat.  It's easy to just add a relay into the circuit, turn the built-in timer to 'always on', and have the node control the on-off times (just in case, I will add a manual switch parallel to the arduino-controlled relay, so that we can always fall back to the build-in control).

We can do more than just provide a better control of the schedules: optimized start up. Instead of pre-programming the startup time of the boiler in the morning, we can sense the external temperature over night, and then delay starting the heating to the last possible moment. The longer the house remains cool over night, the less heat we lose. There' a possible downside to this though: it could increase our consumption. After cold nights, we sometimes find it too cold for our taste in the kitchen - we've under-heated. With optimal startup, the kitchen should always be reasonably warm when we need it, but that might mean coming on earlier than we'd program it to.

Ideally, I'd want to control the temperature setting, but that would require a more invasive change to the boiler. It has a potentiometer for setting the heating circuit temperature. I'd have to either somehow connect a motor to turn the potentiometer, or replace the potentiometer with something like a switched resistor ladder. Varying the temperature throughout the day should improve the efficiency of the boiler, but that's something that may have to wait.

Update I've realized that I can find out something else: the flow through the heating circuit depends only on the state of the thermostats in the house. If most of them are closed, the pump will be able to pump less water. If very little water flows (only through the bathroom), I can consider turning off the heating (at least for a while).

The Kitchen Node

In the kitchen, we currently have an ageing X10 based system to switch three light circuits. When we moved in, all three lights were on the same circuit, so the kitchen was either dark or blazing. I couldn't reach all the wires to put in a new threeway switch, so I had to fit a remote system. It's not terribly robust, there is a noticeable delay between pressing the button and the light switching, and the switch itself is not very intuitive (I keep pressing the wrong buttons). 

The first task for the new system will therefore be to replace the X10 relays. The controller will be a USB jeenode. After looking at many different arduino based systems, my conclusion is that jeenodes offer the best design for my home system - they are very cheap, have radio built in, convenient connectors, and offer a small form factor.

I initially planned to use two Relay plugs for the three lights, but in the end decided to go for three relay nodes from a different supplier (Ciseco). My budget is very tight, and this option is a bit cheaper - they'll be wired straight to the jeenode's pins (using up two of the four connectors). I've also dropped the jeenode's carrier board and box - I'm sure I can find two plastic boxes, one for the node, and one for the relays to keep the high voltage bits separate.

On one of the remaining connectors, I'll connect a temperature sensor. The room board would be nice, but had to go for now;I can add that later when there's a bit more money.

Home Energy Controller

And this is my big new project: building a system that makes it easy to control and monitor the energy we use at home.

I have a strong interest in environmental conservation, and in energy use. I took part in Nesta/UKERC's Carbon Crucible program, and I had EPSRC funding for a feasibility study in analysis of energy monitoring data. The UK is trailing behind many other EU nations when it comes to real, implemented CO reductions (they just keep announcing things and then not realizing them). Taking action locally seems the only way to achieve at least some level of improvement.

The other reason for this project is that I want to build up some experience in embedded devices, play a bit more with Android, and after a long break get back to tinkering with electronics.

It all started with the Raspberry Pi excitement - $25 for a small but powerful Linux based computer - so many things one can do with it. Initially I was thinking about connecting to the systems in our car (I am currently working with an automotive engineering company),  but then I found the Open Energy Monitor page - offering open hardware and software for home energy monitoring. That seemed a much more useful project - and one where I could justify (to myself and the rest of the family) spending the time and money.

The current plan calls for three nodes: one in the kitchen, providing the user interface and replacing the ageing X10 based light control; one in the laundry controlling and metering the boiler, and one in the lobby metering gas, electricity, and quite a few temperatures indoors and outside. The overall bill of parts should hopefully stay bellow £250.