Using a pizza oven for reflow soldering has already been done a million times by hackers/makers all over the world. You can even buy a ready made reflow controllers for such setups. Still, I will present my approach here since it is a little bit different from others I have seen so far.
Most setups use a relay to switch the heating element on/off. Some designs use a SSR and even have elaborate features like zero-crossing-detect. However, I didnt want to mess around with mains voltage. Thats why I decided to use a DMX512-Dimmer do control the heating element. When you think about it, its just another kind of lamp. So why not use a device made to control lamps?
The actual control is done with a Raspberry-Pi. I used a “max6667” Thermocouple amplifier from ebay which is interfaced via SPI. Fortunately there was enought sample code available on the net, I only had to do a litte copy&paste to get it running. I did modify the code to use the py-spidev library. My sourcecode is attached to this post. I also used python to run the PID-Temperature-Loop. Since that code is really ugly I wont publish it now 😀
Here is a picture of the complete Setup:
I did label some of the Items on the picture:
- max6667 board
- DMX Dimmerpack
- Raspberry Pi
- Temperature Monitor for Control/Debugging
As mentioned above, a PID-Algorithm was used to control the temperature. The Profile is rather slow, but it does work. I might add insulation to the oven to allow faster heating.
Modified max6667-lib: max6667