Having completed all the milestones in the project plan, you should have a functioning home hub, with the knowledge to customise and configure it to meet your own requirements.
What I would like to do now is consider some more advanced topics and modules that will greatly add to the value of the hub. The first area to consider is sensors. We have deployed the AM2302 family successfully, but there is a limitation in terms of cable distance. This could be a showstopper, preventing the hub design from being usable in your property. I want to describe three solutions, each being applicable to progressively longer distances between hub and sensor, and each having advantages and disadvantages. Here is a table which enables the comparison:
| Sensor Type | Max Distance | Feature Summary |
|---|---|---|
| AM2302 Family | 4-5m | * Cheap * Single Pin |
| BME280 | 10-15m | * Cheap * Complex electronics * Pi only has 1 serial port |
| Slave Hub | 15-25m | * Cheap * Complex configuration |
| Remote Meteorology | 10-100km | * Free * Not locally representative |
From this table you will be able to determine which approach best meets your requirements.
Having this design operational in my house for a number of months I have learnt some lessons. The Raspberry Pi is a fantastic device for hosting this application, but its Achilles heel is the SD card. Perhaps it’s the number of writes being made by the database and the logging. For this reason I added a USB hard disk to my master hub and the reliability has greatly increased. I followed this excellent walk through.
First up, I will describe the Slave Hub solution, as this builds on the work already done.