Kiln Controller

Turns a Raspberry Pi into a cheap, web-enabled kiln controller.

Features

• easy to create new kiln schedules and edit / modify existing schedules
• no limit to runtime - fire for days if you want
• view status from multiple devices at once - computer, tablet etc
• firing cost estimate
• NIST-linearized conversion for accurate K type thermocouple readings
• supports PID parameters you tune to your kiln
• monitors temperature in kiln after schedule has ended

Run Kiln Schedule

Edit Kiln Schedule

Hardware

Parts

Image	Hardware	Description
	Raspberry Pi	Virtually any Raspberry Pi will work since only a few GPIO pins are being used.
	MAX 31855	Thermocouple breakout board
	K-Type Thermocouple	Invest in a heavy duty, ceramic, k-type thermocouple designed for kilns
	Breadboard	breadboard, ribbon cable, connector for pi's gpio pins & connecting wires
	Solid State Relay	Zero crossing, make sure it can handle the max current of your kiln. You only need one SSR, even if the kiln is 220V. Relays this big always require a heat sink.
	Electric Kiln	There are many old electric kilns on the market that don't have digital controls. You can pick one up on the used market cheaply. This controller will work with 110V or 220V (pick a proper SSR). My kiln is a Skutt KS-1018.

Schematic

The pi has three gpio pins connected to the MAX31855 chip. D0 is configured as an input and CS and CLK are outputs. The signal that controls the solid state relay starts as a gpio output which drives a transistor acting as a switch in front of it. This transistor provides 5V and plenty of current to control the ssr. Since only four gpio pins are in use, any pi can be used for this project. See the config file for gpio pin configuration.

Note: I tried to power my ssr directly using a gpio pin. The pin could not provide enough current (16ma max) to control my ssr. My ssr was rated at 25ma max current, and 3V minimum to switch so I figured it would work. YMMV.

Software

Raspbian

Download NOOBs. Copy files to an SD card. Install raspbian on RPi using NOOBs.

$ sudo apt-get install python-pip python-dev libevent-dev python-virtualenv
$ git clone https://github.com/jbruce12000/kiln-controller.git
$ cd kiln-controller
$ virtualenv venv
$ source venv/bin/activate
$ pip install greenlet bottle gevent gevent-websocket

Note: The above steps work on ubuntu if you prefer

Raspberry PI deployment

If you want to deploy the code on a PI for production:

$ cd kiln-controller
$ virtualenv venv
$ source venv/bin/activate
$ pip install RPi.GPIO

If you also want to use the in-kernel SPI drivers with a MAX31855 sensor:

$ pip install Adafruit-MAX31855

Configuration

All parameters are defined in config.py, just copy the example and review/change to your mind's content.

$ cp config.py.EXAMPLE config.py

Usage

Server Startup

$ source venv/bin/activate; ./kiln-controller.py

Autostart Server onBoot

If you want the server to autostart on boot, run the following commands

$ /home/pi/kiln-controller/start-on-boot

Client Access

Click http://127.0.0.1:8081 for local development or the IP of your PI and the port defined in config.py (default 8081).

Simulation

Select a profile and click Start. If you do not have a raspberry pi connected and configured, then your run will be simulated. Simulations run at near real time and kiln characteristics are defined in config.py.

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

Support & Contact

Please use the issue tracker for project related issues. If you're having trouble with hardware, I did too. Here is a troubleshooting guide I created for testing RPi gpio pins.