Water Tank Sensors

The Pi running OpenHab is directly below the hot water tank, so rather than adding another wireless node in the airing cupboard, I can run some wired sensors.

Simplest for this purpose is a bunch of DS18B20 sensors, these use a 1-wire protocol which is capable of going the 3-4metre distance. Also only need a three wire cable to connect all the sensors. Used an old mini-circuits box to connect the three sensor cables together with 5kohm resistor pull up in the airing cupboard.

Follow instructions @ https://community.openhab.org/t/gpio-1-wire-temp-sensors-on-raspberry-pi-with-openhabian/20941

On the Pi added the following to /boot/config.txt

# PS - Enable 1-wire sensors
dtoverlay=w1-gpio,gpiopin=4

Created a simple bash script to get the temperature /etc/openhab2/scripts/w1:

#!/bin/bash
cat /sys/bus/w1/devices/$1/w1_slave | grep 't=' | sed 's/.*t=\(..\)\(...\)/\1.\2/'

Use exec binding to create 3 things to monitor the three temperature sensors.

Self Build Temperature Sensor

First pass, using NodeMCU and sensor, powered via USB charger. Since a lot of the wireless technology is based on the ESP SOC this would be a good development platform to experiment with, so worth getting one to play with.

Start with a NodeMCU, a simple Temperature Sensor and one of the many USB power bricks lying around the house.

Solder (badly) the BME280 to a four core cable with a couple of two pin header connectors (GND, 3.3V) & (SCL, SDA) on the end. Connect to the pins on the NodeMCU (GND, 3.3V) & (D4, D5).

Install ESPEasy and configure it to have one BME280 device, connected using MQTT ultimately to OpenHAB. In the meantime tested connectivity by installing Mosquitto on my server. Named the ESP in the living room: “Lounge” and the BME280 sensor “Sensor”:

mosquitto_sub -v -t "/Lounge/Sensor/#"
/Lounge/Sensor/status/LWT Connected
/Lounge/Sensor/Temperature 16.24
/Lounge/Sensor/Humidity 54.18
/Lounge/Sensor/Pressure 1021.65

Too easy, but pretty ugly, with a USB charger hanging out of the wall socket.

Build two more using D1 mini boards, soldering the wires direct to the through hole vias. Deploy one as ‘BigShed’ and the other as ‘TopRoom’.

Open HAB

Install a new power socket in the Utility room, with 5V (3.1A) USB output. Run network cable from switch in loft to the Utility room.

Need one Raspberry PI I went for the 3B+, probably could of got away with something lower power. With a suitable SD Card.

Install Open HAB following the instructions on the openHab website.

Radiator Zones

Could control individual radiators using thermal actuators controlled using Sonoff basic wifi switches to turn on and off. Actuators based on heating wax should be silent if a little slow to respond. 3-4 minutes to open or close.

Disadvantages of this system are:

  • need mains power near every radiator that needs to be controlled, typically sockets are not near radiators.
  • Need one on every radiator in a room
  • If the system fails, have to manually switch each basic on, to get any heat to the radiator.

Alternative is to install motorised valves to zone the heating system, again controlled by Sonoff basics (or just cabled to the heating controller). These would typically be hidden under floorboards.

  • Need to know the complete layout of the heating pipes to be able to decide where to insert the values.
  • Likely need to install more plumbing to create zones.
  • As hidden under floorboards, failure of the valves would cut heat to that zone until it is replaced.
  • Need to lift floorboards, ground floor pipes are under concrete so no scope to install.
  • Only useful if areas can be zoned, which rooms to group together?

Energy Monitor

My hardware skills being next to non-existent am relying on bolting some pre-built hardware together. A good starting point is open energy monitor. project. Simplest scheme, using the existing Raspberry Pi that is hosting the Home Server is something based on:

Firmware for the Arduino is here: https://github.com/openenergymonitor/emontx-shield

ZigBee Bridge

To add ZigBee sensors to the network we need a bridge, the one that keeps popping up is zigbee2mqtt. This is a USB based solution that is plugged into an existing PC or Raspberry Pi. Which is probably okay for my scenario as the Pi is at one end of the house and the server is centrally located, so will probably give enough coverage.

There is also the option of making it into a ‘router’ – a standalone repeater, or can be connected to an ESP8266 to form a serial socket over WiFi to the Home Server.

The development kit consists of:

Temperature and Humidity Sensors

Adding inexpensive sensors to all rooms, is the first step in enabling a much more responsive and efficient heating system.

Thermostatic valves on radiators are okay, but they never seem to work as well as one would hope. Radiators in ‘cool’ rooms (toilets/hall) getting red hot whilst radiators in ‘warm’ rooms (lounge/snug) getting starved of heat. Having the thermostat connected to the thing providing the heat is always going to be a compromise.

Inexpensive, simple battery powered temperature sensors that connect using zigbee or zwave devices are available that can be slowly added to key rooms as required.

Having historical temperature data for all the rooms in the house, will help to identify rooms that are cooling down or warming up too quickly. So even with a manual heating system will allow me to make improvements. For example replacing a radiators or rebalancing the system. Identifying rooms that are loosing too much heat through drafts or voids in the insulation.

Sensors

Two obvious candidates are very low power battery based devices that periodically transmit the temperature and humidity, using Zigbee or similar low power RF. Or 5V powered WiFi devices, e.g. based on the ESP8266 or similar plus a sensor board.

Off the Shelf ZigBee Sensor

  • Does not need programming, works out of the box
  • Cable free, can be placed anywhere in the room
  • Inexpensive (£10 per sensor)
  • Batteries will run down (every 3 months?)
  • Low update rate means slow to react to local changes, fine for monitoring
  • Needs a gateway to connect to the Home Server
  • Short range, might need two or more gateways

Self Built WiFI Device

  • Long Range
  • Connects to existing WiFi network
  • Very responsive, can send updates on change rather than (just) periodically
  • Mains powered so no batteries to exhaust
  • Flexible, can repurpose the ESP to do other tasks
  • Requires flashing
  • Is Wired, need to be near a socket
  • Ugly cables
  • Inexpensive (£10 per sensor)
  • Needs a power brick / 5v

Conclusion

To start with get both types of sensor, to evaluate the range and battery life of the ZigBee sensors. The ESP based device is a useful development platform for other smart bits and bobs so worth building a development kit and environment.

Initially only get one of each, and use them to do week long surveys of each room in the house to see what the warming/cooling profile is like.

Assuming build up a whole house network, will need around 13 sensors:

  • Lounge * 2
  • Kitchen
  • Study
  • Bed 1
  • Bed 2
  • Bed 3
  • Bed 4
  • Top Room
  • Henry’s Den
  • Ensuite
  • Bathroom
  • Outdoors

Rooms / Areas that are not monitored:

  • Porch
  • Hall
  • Downstairs Loo
  • Landing
  • Utility Room

Although unlikely to need to control the temperature in the bathrooms (these are ‘always on’ rooms) in the future may want to monitor humidity and control the ventilation level.

If using Zigbee sensors then also need to add a gateway device, assuming I add a Zigbee gateway to the Home Server

SMART Home Introduction

New house… …new project. This one I am going to slowly add various smart technology and monitoring to my home.

Key requirements are that it is low cost, based on open source and does not rely on 3rd party closed systems and servers.

Currently looking at OpenHAB as the main server, running on a Raspberry Pi.

Will slowly add more functionality as money, time and support becomes available, some hardware I would like to add:

  • Energy Monitoring, to have real-time access to Solar PV generation and whole home energy usage, probably based on Open Energy Monitor. Just by adding the appropriate sensors
  • Room Temperature and Humidity sensors for the whole house.
  • Control and monitoring of the Heating and Hot Water
  • Linking to home security sensors, room sensors, door and window switches.
  • Integration into Alexa / Google Home / Phone App.

Temperature and Humidity Sensors

Adding inexpensive sensors to all rooms, is the first step in enabling a much more responsive and efficient heating system.

Thermostatic valves on radiators are okay, but they never seem to work as well as one would hope. Radiators in ‘cool’ rooms (toilets/hall) getting red hot whilst radiators in ‘warm’ rooms (lounge/snug) getting starved of heat. Having the thermostat connected to the thing providing the heat is always going to be a compromise.

Inexpensive, simple battery powered temperature sensors that connect using zigbee or zwave devices are available that can be slowly added to key rooms as required.