silvia-pi

A Raspberry Pi modification to the Rancilio Silvia Espresso Machine implementing PID temperature control.

Currently Implemented Features:

• Brew temperature control
• RESTful API
• Web interface for displaying temperature and other statistics
• Programmable machine warm-up/wake-up

Planned Features:

• Steam temperature control
• Timed shots with pre-infusion
• Digital pressure gauge

Dashboard

Hardware

• Raspberry Pi 2
  • $35 - http://www.amazon.com/Raspberry-Pi-Model-Project-Board/dp/B00T2U7R7I
  • $5 - Raspberry Pi Zero should work too
• Wi-Fi Adapter that works with Raspbian
  • $10 - http://www.amazon.com/Edimax-EW-7811Un-150Mbps-Raspberry-Supports/dp/B003MTTJOY or
  • $10 - http://www.amazon.com/Tenda-150Mbps-Wireless-Adapter-W311MI/dp/B006GCYAOI
• Power Adapter
  • Any Micro USB 5v / 2A supply will do, the longer the cable the better
  • $9 - http://www.amazon.com/CanaKit-Raspberry-Supply-Adapter-Charger/dp/B00GF9T3I0
• Micro SD Card
  • 4GB minimum, 8GB Class 10 recommended
  • $7 - http://www.amazon.com/Samsung-Class-Adapter-MB-MP16DA-AM/dp/B00IVPU7KE
• Solid State Relay - For switching on and off the heating element
  • $10 - https://www.sparkfun.com/products/13015
• Thermocouple Amplifier - For interfacing between the Raspberry Pi and Thermocouple temperature probe
  • $15 - https://www.sparkfun.com/products/13266
• Type K Thermocouple - For accurate temperature measurement
  • $15 - http://www.auberins.com/index.php?main_page=product_info&cPath=20_3&products_id=307
• Ribbon Cable - For connecting everything together
  • $7 - http://www.amazon.com/Veewon-Flexible-Multicolored-Female-Breadboard/dp/B00N7XX4XM
    • Female to Female if using the Raspberry Pi 2
  • $5 - http://www.amazon.com/uxcell-Width-Colorful-Flexible-Ribbon/dp/B00BWFY6JI
    • Bare wire if using the Raspberry Pi Zero
• 14 gauge wire - For connecting the A/C side of the relay to the circuit
  • $5 - Hardware Store / Scrap
    • Don't skimp here. Remember this wire will be in close proximit to a ~240*F boiler

Hardware Installation

Installation Instructions / Pictures

Circuit Diagram

High-level circuit diagram:

Software

• OS - Raspbian Jessie
  • Full - https://downloads.raspberrypi.org/raspbian_latest
  • Lite (for smaller SD Cards) - https://downloads.raspberrypi.org/raspbian_lite_latest

Install Raspbian and configure Wi-Fi and timezone.

silvia-pi Software Installation Instructions

Execute on the pi bash shell:

sudo apt-get -y update
sudo apt-get -y upgrade
sudo apt-get -y install rpi-update git build-essential python-dev python-smbus python-pip
sudo rpi-update
sudo bash -c 'echo "dtparam=spi=on" >> /boot/config.txt'
sudo reboot

After the reboot:

sudo git clone https://github.com/brycesub/silvia-pi.git /root/silvia-pi
sudo /root/silvia-pi/setup.sh

This last step will download the necessariy python libraries and install the silvia-pi software in /root/silvia-pi

It also creates an entry in /etc/rc.local to start the software on every boot.

API Documentation

GET /allstats

Returns JSON of all the following statistics:

• i : Current loop iterator value (increases 10x per second)
• tempf : Temperature in °F
• avgtemp : Average temperature over the last 10 cycles (1 second) in °F
• settemp : Current set (goal) temperature in °F
• iscold : True if the temp was <120°F in the last 15 minutes
• hestat : 0 if heating element is currently off, 1 if heating element is currently on
• pidval : PID output from the last cycle
• avgpid : Average PID output over the last 10 cycles (1 second)
• pterm : PID P Term value (Proportional error)
• iterm : PID I Term value (Integral error)
• dterm : PID D Term value (Derivative error)
• snooze : Current or last snooze time, a string in the format HH:MM (24 hour)
• snoozeon : true if machine is currently snoozing, false if machine is not snoozing

GET /curtemp

Returns string of the current temperature in °F

GET /settemp

Returns string of the current set (goal) temperature in °F

POST /settemp

Expects one input 'settemp' with a value between 200-260.
Sets the set (goal) temperature in °F Returns the set temp back or a 400 error if unsuccessful.

GET /snooze

Returns string of the current or last snooze time formatted "HH:MM" (24 hour).
e.g. 13:00 if snoozing until 1:00 PM local time.

POST /snooze

Expects one input 'snooze', a string in the format "HH:MM" (24 hour).
This enables the snooze function, the machine will sleep until the time specified.
Returns the snooze time set or 400 if passed an invalid input.

POST /resetsnooze

Disables/cancels the current snooze functionality.
Returns true always.

GET /restart

Issues a reboot command to the Raspberry Pi.

GET /healthcheck

A simple healthcheck to see if the webserver thread is repsonding.
Returns string 'OK'.