thermostat

Thermostat which drives the room temperature +2 degrees above the outside temp.

These are the building blocks for the project:

• Raspberry Pi 3 running balenaCloud IoT environment for easy remote access & updates
• Local network with 3G-WLAN hotspot
• Room temperature with Wemos D1 & DS18B20 thermocouple sensor
• Outdoor temperature from Finnish Meteorological Institute
• WLAN Relay Deltaco Smartplug SH-P01 reflashed with ESPhome. The relay can be controlled with ESPhome REST API.

How this works:

1. balenaCloud uploads and executes the code in the Raspberry Pi (Server)
2. Server gets the outdoor temperature from FMI API
3. Server gets the indoor temperature from a Wemos D1 sensor which broadcasts temperature to LAN every two seconds
4. Server runs the SH-P01 relay(s) via WiFi

Sensor

To build a sensor you need:

• Wemos D1 microcontroller
• DS18B20 temperature sensor
• 4,7 kOhm resistor
• PlatformIO build environment

Connect the Wemos D1 pins (Dn) to DS18B20 sensor in a following manner:

Wemos D1   DS18B20
 3,3        VCC (red)
 G          GND (black)
 D7         data (yellow)

• Connect Wemos D1 pins 3,3 and D7 with 4,7 kOhm resistor

Building:

1. Configure your sensor by editing include/settings.cpp and sensor/include/settings.cpp (get the templates from settings.cpp.sample files). The best practice is to create sensor-specific file sensor/include/settings_mysensor.cpp and activate this with sensor/set_current_sensor.sh.

   By using OTA DRIVE cloud service you can set only the OTA_DRIVE_APIKEY value in the sensor/include/settings.cpp and download rest values from the service. This way you can set all device-specific values as an OTA DRIVE configuration and use same firmware for all your sensors.

2. Build, upload and execute the firmware:

   cd sensor
   ./set_current_sensor.sh mysensor
   make upload
   

3. Check Wemos D1 led:

• Blinking quickly (200 ms cycle): trying to connect to WiFi
• Blinking slowly (2000 ms cycle): sending temperature data as UDP packets

1. Dump the broadcast messages using tcpdump:

   $ sudo tcpdump -A port 3490
   tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
   listening on eno1, link-type EN10MB (Ethernet), capture size 262144 bytes
   10:09:59.678357 IP 192.168.49.101.3490 > 192.168.49.255.3490: UDP, length 14
   E..*.x........1e..1.........Sensor 1:24.00....
   10:10:01.719360 IP 192.168.49.101.3490 > 192.168.49.255.3490: UDP, length 14
   E..*.y........1e..1.........Sensor 1:24.75....
   

Error Codes

In case of error the internal led is on for 5 seconds. After this it shows the error code with 0,5 second blinks. See grep showError sensor/src/sensor.cpp for error codes.

Configuration and OTA Update Using OTA DRIVE

OTA DRIVE is an cloud service for updating and configuring MCUs. Temperature sensors can be updated and configured through the service.

• In include/settings.cpp set the OTA_DRIVE_APIKEY which you get from your OTA DRIVE product.
• Set following JSON to the default configuration:

  {
   "sensorName": "<!--not-set-->",
   "influxDbToken": "<!---->",
   "deepSleepSeconds": "<!--300-->",
   "ledBlink": "<!--1-->"
  }
  

• Add new devices one by one. This way you can add individual sensor names and InfluxDB tokens for each device from the device settings.
• Precedence of the values:
  1. OTA DRIVE device-specific values
  2. OTA DRIVE default values
  3. firmware values from sensor/include/settings.cpp

To deploy a new firmware version

• Update SENSOR_FW_VERSION string in the top of sensor/src/sensor.cpp
• In sensor/, run make build to build the new firmware
• Upload .pio/build/wemosd1/firmware.bin to OTA DRIVE
• Assign the new version to your device group
• Enjoy monitoring successfull upgrades

Configuration

The parameters for the script are given as balenaCloud variables which are shown to the application as environment vars.

Essential variables:

• THERMOSTAT_DELAY_BETWEEN Delay between execution cycles in seconds. Type: integer
• THERMOSTAT_TEMP_DIFF The desired temperature difference between outdoor and indoor temperatures. A positive value sets indoor temperature higher than the outdoor temperature. Type: integer
• SENSOR_BCAST_IP Broadcast IP to listen for sensor messages. This should be a broadcast IP of your LAN (e.g. 192.168.0.255). If empty, binds to all addresses. Type: string

Defining inputs (ESP8266 sensors):

• SENSOR_INDOOR Comma-separated list of indoor temperature sensors. These names refer to the names broadcasted by the temperature sensors (see above). Type: comma-separated list of strings
• SENSOR_OUTDOOR Similair comma-separated list of outdoor temperature sensors. Tyoe: comma-separated list of strings

Defining outputs (ESPhome relays):

• RELAY_NAME ESPhome mDNS device name (e.g. relay_4.local). Each device must have a key and API password defined. See below. Type: comma-separated list of strings
• RELAY_KEY Device key (e.g. relay_4_deltaco_sh-p01) of the particular input to control. The keys are enumerated to the debug log /var/log/thermostat.log after the device is connected. Type: comma-separated list of strings
• RELAY_PASSWORD API password for the device. Type: comma-separated list of strings

Optional variables:

• THERMOSTAT_FORCE_ON If contains a value (e.g. yes) the relay is forced ON/closed to turn the heating on regardless of the temperatures. Type: string
• THERMOSTAT_FORCE_OFF If contains a value (e.g. yes) the relay is forced OFF/open to turn the heating off regardless of the temperatures. Type: string
• THERMOSTAT_TEMP_MAX Maximum room temperature. If the indoor temperature raises above this limit the relay is always turned off. Type: integer

Nord Pool variables (optional):

To give different values to thermostat while the current Nord Pool electricity price is low (related to other hours of the day) you can use following variables:

• NORDPOOL_AREA Set this to your Nord Pool area (e.g. FI, EE). Type: string
• NORDPOOL_TZ Timezone descriptor which can be given directly to pytz. Type: string
• NORDPOOL_HOURS Defines the number of cheapest hours of the day. Value 5 searches five cheapest hours in the current day. Type: integer
• THERMOSTAT_TEMP_DIFF_CHEAP Overrides the default THERMOSTAT_TEMP_DIFF value during the Nord Pool cheap hours. Type: integer

InfluxDB variables (optional):

The InfluxDB variables allow the server to send relay status to InfluxDB. By configuring this and corresponding sensor variables you can send monitoring data to the defined InfluxDB.

• INFLUXDB_URL URL of the InfluxDB server (e.g. https://your.influxdb:8086). Type: string
• INFLUXDB_ORG InfluxDB organisation. Type: string
• INFLUXDB_BUCKET InfluxDB bucket. Type: string
• INFLUXDB_TOKEN InfluxDB access token. The server needs write access to the given bucket. Type: string
• INFLUXDB_SSL_CERT_BASE64 InfluxDB server SSL certificate chain. See below how to get this. Type: string

To get the base64-encoded cert do following:

1. Open your InfluxDB server with Firefox
2. Click the lock icon (left of URL) > Connection secure > More information > View certificate > Download the certificate chain in PEM format as cert.pem
3. cat cert.pem | base64 -w0 >cert.b64
4. Copy cert.b64 to INFLUXDB_SSL_CERT_BASE64

Variables for testing and debugging:

To run Thermostat without real temperature sensors set SENSOR_INDOOR and SENSOR_OUTDOOR to _test_. You can set the phony temperature values using environment variables TEST_TEMP_INDOOR and TEST_TEMP_OUTDOOR.

Similair magic INFLUXDB_URL value _test_ puts InfluxDB reporter to test mode and just prints the values to STDERR.

If there are no relays just set empty values to RELAY_NAME, RELAY_KEY and RELAY_PASSWORD.

Defining devices (example):

• One device: RELAY_NAME=relay_1.local RELAY_KEY=relay1_deltaco_sh-p01 RELAY_PASSWORD=relay1apipassword
• Two (or more) devices: RELAY_NAME=relay_1.local,relay_2.local RELAY_KEY=relay1_deltaco_sh-p01,relay2_deltaco_sh-p01 RELAY_PASSWORD=relay1apipassword,relay2apipassword

Nord Pool configuration (example):

The aim of the Nord Pool features is to allow thermostat to heat the house more during the cheapers hours of the day and less during the more expensive time slots. This mechanism retrieves the Nord Pool price data for the given area and calculates the cheapest hours.

THERMOSTAT_TEMP_DIFF=1
NORDPOOL_AREA=FI
NORDPOOL_TZ=EET
NORDPOOL_HOURS=8
THERMOSTAT_TEMP_DIFF=5

The above configuration heats the house more during the cheapest eight hours (difference between outdoor and indoor temperature should be more than five degrees) and less during the 16 more expensive hours.

You should follow the temperatures to find best values for your site. InfluxDB is perfect tool for monitoring purposes.

Short Balena Local Mode Command Summmary

Start by enabling Local Mode from your device. This can be done in the BalenaCloud Management UI (see Balena docs).

• sudo balena scan gives you the device address in your local network, e.g. 7064e4d.local
• balena push ADDRESS pushes your local codebase to device, e.g. balena push 7064e4d.local
• sudo balena ssh ADDRESS MY-SERVICE opens ssh connection inside the container. The default service name is main, e.g. balena ssh 7064e4d.local main

Publishing to production (Balena)

• Make sure you have installed balena CLI tool
• Get your fleet name from balenaCloud UI
• balena login
• balena push <your fleet name>
• In balenaCloud UI go to the fleet > Summary and make Releases selection to point to your latest release.