Turns a Raspberry Pi into an inexpensive, web-enabled kiln controller.
- 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
- api for starting and stopping at any point in a schedule
- supports MAX31856 and MAX31855 thermocouple boards
- support for K, J, N, R, S, T, E, or B type thermocouples
- accurate simulation
- support for shifting schedule when kiln cannot heat quickly enough
- support for preventing initial integral wind-up
Run Kiln Schedule
Edit Kiln Schedule
Image | Hardware | Description |
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Raspberry Pi | Virtually any Raspberry Pi will work since only a few GPIO pins are being used. |
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MAX31855 or MAX31856 | Thermocouple breakout board |
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K-Type Thermocouple | Invest in a heavy duty, ceramic, k-type thermocouple designed for kilns |
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Breadboard | breadboard, ribbon cable, connector for pi's gpio pins & connecting wires |
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Solid State Relay | Zero crossing, make sure it can handle the max current of your kiln. Even if the kiln is 220V you can buy a single 3 Phase SSR. It's like having 3 SSRs in one. Relays this big always require a heat sink. |
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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. |
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.
My controller plugs into the wall, and the kiln plugs into the controller.
WARNING This project involves high voltages and high currents. Please make sure that anything you build conforms to local electrical codes and aligns with industry best practices.
Note: I tried to power my ssr directly using a gpio pin, but it did not work. My ssr required 25ma to switch and rpi's gpio could only provide 16ma. YMMV.
Download Raspberry PI OS. Use Rasberry PI Imaging tool to install the OS on an SD card. Boot the OS, open a terminal and...
$ sudo apt-get update
$ sudo apt-get dist-upgrade
$ sudo apt-get install python3-virtualenv libevent-dev virtualenv
$ git clone https://github.com/jbruce12000/kiln-controller
$ cd kiln-controller
$ virtualenv -p python3 venv
$ source venv/bin/activate
$ pip install --upgrade setuptools
$ pip install greenlet bottle gevent gevent-websocket
Note: The above steps work on ubuntu if you prefer
If you want to deploy the code on a PI for production:
$ cd kiln-controller
$ virtualenv -p python3 venv
$ source venv/bin/activate
$ pip install -r requirements.txt
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
You should change, test, and verify PID parameters in config.py. Here is a PID Tuning Guide.
You may want to change the configuration parameter sensor_time_wait. It's the duty cycle for the entire system. It's set to two seconds by default which means that a decision is made every 2s about whether to turn on relay[s] and for how long. If you use mechanical relays, you may want to increase this. At 2s, my SSR switches 11,000 times in 13 hours.
$ source venv/bin/activate; ./kiln-controller.py
If you want the server to autostart on boot, run the following command:
$ /home/pi/kiln-controller/start-on-boot
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).
In config.py, set simulate=True. Start the server and select a profile and click Start. Simulations run at near real time.
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/.
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.
This project was originally forked from https://github.com/apollo-ng/picoReflow but has diverged a large amount.