Rancilio Silvia PID

Yet another implementation of a PID controller for the Rancilio Silvia Coffee Machine. Using an ESP32 (ESP8266 should work as well) with a solid state relay and a TSIC 306 temperature probe the boiler temperature can be controller within one degree celsius.

The coffee machine connects to a MQTT broker to publish sensor data. Control parameters for the pid loop can also be set via MQTT topics. These topics can be used to integrate the coffee maker into home assistant.

The firmware can be updated via the OTA endpoint /update.

Table of Contents

• Rancilio Silvia PID
  • Table of Contents
  • Hardware
    • ESP 32 NodeMCU Dev Kit C
    • TSIC 306 Temperature Probes
    • Solid State Relay
  • Setup
  • OTAU
  • MQTT Topics
    • Availability Topics
    • Sensor Topics
    • Control Topics
      • Target
      • Coldstart
      • Window
      • Cycle
      • P Value
      • I Value
      • D Value
  • Contributing
  • Thanks and Credits
  • License

Hardware

ESP 32 NodeMCU Dev Kit C

This is the microcontroller running the code. Other variants of the ESP32 and the ESP8266 should work as well, but I have not tested this.

TSIC 306 Temperature Probes

These temperature probes provide accurate measurements up to 150°C and are used to measure the boiler and grouphead temperature. The connected pins can be configured in the Pins.h header file.

Solid State Relay

The relay is used to switch the heating coil of the boiler on and off. A solid state relay is chosen to provide fast switching without wear and click noises. The heating element can draw up to 1.3 kW which must be compatible with the relay specs. The connected pins can be configured in the Pins.h header file.

Setup

Copy the File Credentials.h.sample and rename it to Credentials.h and set appropriate values.

Do the same for MqttConfig.h.sample. Explanation for the topics is provided below in the section MQTT Topics.

OTAU

The firmware of the coffee machine can be updated via OTAU using the /update endpoint. The hostname of the device can be cofigured with the HOSTNAME setting.

MQTT Topics

MQTT is used to communicate with the coffee machine. The topics are configured in the MqttConfig.h. The Client Id of the device it defined by the MQTT_CLIENTID setting.

Availability Topics

MQTT_STATE_TOPIC

This topic can be used to check if the coffee machine is turned on by checking for the message on which will be published continously according to the MQTT_HEARTBEAT_INTERVAL_MS setting.

Sensor Topics

These values are published by the coffee machine when they change their values. Max rate is configured by the MQTT_PUBLISH_INTERVAL_MS setting.

Entity	Setting	Value
Boiler Temperature	MQTT_BOILER_TOPIC	double / Temperature
Grouphead Temperature	MQTT_HEAD_TOPIC	double / Temperature
PID Output	MQTT_PID_TOPIC	double / Control Output (0-1)
Heater state	MQTT_HEATER_TOPIC	binary / "on" or "off"

Control Topics

These values define the control loop of the boiler heater. These values have read/write topics to set values and retrieve them.

Publish means the coffee machine will publish these topics.

Subscribe means the coffee machine will subscribe to these topics.

Target

Defines the target temperature of the boiler.

Publish	Subscribe
MQTT_TARGET_PUB_TOPIC	MQTT_TARGET_SUB_TOPIC

Coldstart

Defines the boiler temperature until the heater will be constantly turned on to heat up faster in the beginning.

Publish	Subscribe
MQTT_COLDSTART_PUB_TOPIC	MQTT_COLDSTART_SUB_TOPIC

Window

After the boiler reaches the coldstart temperature, the heating element will be controlled based on time slices of this length in milliseconds

Publish	Subscribe
MQTT_WINDOW_PUB_TOPIC	MQTT_WINDOW_SUB_TOPIC

Cycle

This value is a normalized double from 0-1. The defined value is the maximum proportion of the window the heating element can be turned on. E.g. cycle of 0.2 with a window of 1000 ms means the heating element can turn on at max 200 ms out of every 1000 ms.

Publish	Subscribe
MQTT_CYCLE_PUB_TOPIC	MQTT_CYCLE_SUB_TOPIC

P Value

Weight of the proportional component. See PID Control for more information.

Publish	Subscribe
MQTT_P_PUB_TOPIC	MQTT_P_SUB_TOPIC

I Value

Weight of the integral component. See PID Control for more information.

Publish	Subscribe
MQTT_I_PUB_TOPIC	MQTT_I_SUB_TOPIC

D Value

Weight of the derivative component. See PID Control for more information.

Publish	Subscribe
MQTT_D_PUB_TOPIC	MQTT_D_SUB_TOPIC

Contributing

Since C++ is not my strongest of languages and this is my first implementation of a pid control loop, there are probably a lot of things that can be done easier or cleaner.

Please feel free to dive in! Open an issue or submit PRs.

Thanks and Credits

Thanks to tripplefox for implementing the TSIC sensor family under MIT license, works just great!

License

MIT © thefipster