Today's post written by HB Cranky, who has spent 18 months designing a house of the future with some software input from Lunarlite.
Heating in Winter
As shown by Nest and Hive, it is a common desire to have more control over home heating. In conversation with a friend in 2013 about the potential of nest (this was pre British Gas announcing hive) it was speculated on the potential of doing a low cost version. Both of our houses already utilised a wireless thermostat and so it was a question of whether we could (cheaply) replace them with something that would give us greater flexibility.
The first question was whether we could decode the signal being sent from the therm to the receiver:
|Drayton (Old Thermostat) for boiler control. We sniffed this using a £0.99 433 receiver, two resistors and Audacity.|
|British Gas rebadged Drayton set. We also sniffed these.|
It was discovered that the boiler control was relatively simple, namely either on or off sent to it every 5 minutes - the receiver would alarm otherwise. The signal itself was also simple, and we quickly progressed to constructing a new transmitter that would give us greater control.
To gain any benefit over the existing thermostat the replacement would have to be more flexible. For it to be of use the following was required:
Remote control of temperature - via a web page / app
'Holiday' modeIntelligent heating - based on external and internal temperatures.
The Central heating ideal temperature is stored in a Google calendar to allow the house temperature to be dictated.
The LCARS web interface is accessible from outside the house using port forwarding.
|433 in-situ Transmitter board attached to Raspberry Pi|
|New Thermostat in situ|
|New Thermostat - Pygame based interface, based on Galilean Thermometer. The Right hand control sphere controls the temperature.|
|Thermostat LCARS (web) interface. Written in Django. The left two columns display temperature readouts (Attic, Barab and Cellar are inside, Eden and Forno are in the garden).|
We use redis to record all the temperatures, queue up the boiler commands and work out how often we need to talk to the boiler. A Django front end provides an interface into the important redis values.
Cooling in SummerOnce the heating had been covered, we had the opposite problem in Summer. How to cool the house automatically. Given that when Velux windows are installed, a remote for each window is provided, there are 3 remotes for only two adults. We asked ourself what we could do with them. Velux use the io-homecontrol which is a proprietary two-way encrypted protocol. When attacked, techies always route around the damage. We decided to solder a load of relays to the remote.
We called this product velpi.
|VelPi. Pi powered velux remote control.|
|Energenie 433 receiver which switches on / off individual sockets.|