This project seeks to replace the OEM control panel on a Lennox Winslow PS40 pellet stove with a Raspberry Pi. I am utilizing a Raspberry Pi 3 Model B+, relays, and temperature snap switches installed on the pellet stove. I chose a Pi 3 for its wireless connectivity and familiarity with the platform. I had previously used an Arduino Nano for a much more rudimentary version of this project and found great difficulty in making adjustments to the code. Additionally the Raspberry Pi platform will allow for expansion in the future to include IoT controls and logging of usage utilizing networked databases. The project will be written using Node.js to handle high-level logic and communications, calling Python scripts to handle interacting with GPIO. I'm now in the process of rewriting this project to a more modern v2. Previously I had settled on using deprecated versions of Node.js to maintain compatibility with various Pi GPIO modules, now I've decided to split the GPIO controls off to a small Python interface script.
Three GPIO pins are used along with a common ground to control three relays, supplying 120VAC power to the igniter and combustion blower when appropriate, and supplying power to the auger motor in pulses. Two more GPIO pins are used to detect open/closed status of a temperature-controlled snap switch and a vacuum switch. Another temperature-controlled snap switch is used to supply power to the convection motor when the pellet stove has reached a suitable temperature. A final temperature-controlled snap switch us used to interrupt the circuit for the auger motor to shut the stove off when an over-temperature condition is met. I will be utilizing a OneWire DS18B20 temperature sensor to detect the temperature of air exiting the stove vents.
For ease of adaption, connection, and prototyping I've decided to use Cat 5 ethernet cabling and RJ45 connectors to connect the Raspberry Pi to the stove, and to a breadboard mockup of the sensors and switches for testing.
