|  | [Raspberry Pi](https://www.adafruit.com/category/105) | Virtually any Raspberry Pi will work since only a few GPIO pins are being used. |
|  | [K-Type Thermocouple](https://www.auberins.com/index.php?main_page=product_info&cPath=20_3&products_id=39) | Invest in a heavy duty, ceramic, k-type thermocouple designed for kilns |
|  | 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](https://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=331). It's like having 3 SSRs in one. 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. |
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](https://github.com/jbruce12000/kiln-controller/blob/master/config.py) file for gpio pin configuration.
**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](https://www.raspberrypi.org/software/). Use Rasberry PI Imaging tool to install the OS on an SD card. Boot the OS, open a terminal and...
If you're done playing around with simulations and want to deploy the code on a Raspberry PI to control a kiln, you'll need to do this in addition to the stuff listed above:
You should change, test, and verify PID parameters in config.py. Here is a [PID Tuning Guide](https://github.com/jbruce12000/kiln-controller/blob/master/docs/pid_tuning.md). There is also an [autotuner](https://github.com/jbruce12000/kiln-controller/blob/master/docs/ziegler_tuning.md). Be patient with tuning. No tuning is perfect across a wide temperature range.
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.
If you're busy and do not want to sit around watching the web interface for problems, there is a watcher.py script which you can run on any machine in your local network or even on the raspberry pi which will watch the kiln-controller process to make sure it is running a schedule, and staying within a pre-defined temperature range. When things go bad, it sends messages to a slack channel you define. I have alerts set on my android phone for that specific slack channel. Here are detailed [instructions](https://github.com/jbruce12000/kiln-controller/blob/master/docs/watcher.md).
If you're having trouble with hardware, I did too. Here is a [troubleshooting guide](https://github.com/jbruce12000/kiln-controller/blob/master/docs/troubleshooting.md) I created for testing RPi gpio pins.
## Origin
This project was originally forked from https://github.com/apollo-ng/picoReflow but has diverged a large amount.
