House central heating

My first wood boiler was initially designed to burn coal and had a manual setpoint for air intake. Every ignition setpoint was different, and burning was considered suboptimal at best. The main idea was to add a Raspberry Pi controllable draft ventilator, an air intake regulator and a chimney temperature sensor. Here is a graph showing how the PID algorithm manages the burning process:

Draft fan

Because the chimney draft was weak at temperatures above 0 degrees Celsius, or powerful at temperatures below -15 degrees Celsius. I had to moderate suction on the chimney side. I managed to buy a draft fan and an impeller, but no adapter to fit it. So I had to design and weld it myself. It was a sort of success story because if the burning temperature was too low, then massive chemical loss clogged up everything, and I got an early indication about the rising issue. But when the temperature was too high, I lost energy or, in extreme cases, started a fire within the chimney. Since the decent setpoints were within a narrow range, I messed up a lot and cleaned this impeller more than needed.

Air intake

Another lever I had for the burning process control was the air intake. This one was easier to automate. I just had to replace manual setpoint screw with stepper motor.

Controller

Controller hardware consists of an ADC for thermocoupler temperature sensing, a solid-state 220V relay for the fan and a servo driver for the door intake adjustment.

Wood gas boiler

Then, after years of service, the old boiler efficiency levels were no longer satisfactory by my standards. The new system had semi-mechanical automation capabilities, like switching the fan off when it is out of fuel. So I had to revive old hardware in a new launchbox.

Since the boiler is relatively airtight, I only needed a fan on/off switching capability based on chimney temperature.