Controller for gasification furnace


Hi everyone. I just found out about Cayenne today, it sounds like it will do what I need. If I can figure it out at least. I’ll try to make this as short as I can.

For those of you who don’t know how a gasifier works I’ll do a quick run down. It has an upper chamber where the wood goes and a lower chamber where the gases from the burning wood goes. There is a blower that forces air into the top chamber which in turn forces the fire to burn upside down through a tube connecting the upper and lower chambers. In order to reburn the exhaust from the fire, more oxygen is injected as it enters the lower chamber. The result is little to no smoke.

Now for the part you all can hopefully help me with. I have the gasifier built, and working, I just want to make it more efficient and slower burning. To do that I need to be able to adjust the blower speed based off of different variables. Ideally I would like to have a K type thermocoupler in the upper chamber, a S type thermocoupler in the lower chamber, and possibly an 02 sensor in the fluestream. With those inputs I would like to be able to control the fan speed and have a dampener, operated by a servo, that adjusts the oxygen that is injected for the secondary burn.

Right now I am just looking for assistance in connecting the thermocouplers, an AC motor(110V) with a VFD, and a servo for the dampener to my Raspberry Pi.

I would greatly appreciate any input. As far as getting the raspi to do what I want it to once I do get everything connected, I ‘think’ I might be able to manage that, but if anyone has tips for that the would definitely be welcomed.


hi @mellowyelloe. welcome to the cayenne community.
This is a nice project you got here. All the sensor you want is not supported on pi agent 2.0. You can either add them to your pi and then send data to cayenne using Or use an Arduino device.


Far as I know, you’ll need to find a small three phase motor for your blower. Last I knew, and it has been a few years since I’ve bought any, but VFD’s only work with three phase. Many VFD’s can convert a single phase 120v input to a 3 phase 220v output.


@shramiksalgaonkar once connected I would then have calibrate the system so that the pi can understand what it means, correct? In other words it’s not plug and play, correct?

@mlappin how would you suggest to proportionally control the speed of a fan or a service for what I am needing? Sorry I don’t know much about designing electrical devices or programming.


@mellowyelloe can you provide more detail on what you mean by calibrate the system?


Most of the VFD’s I’ve used will accept a digital or analog signal. I’m sure the Pi could control a signal of some kind to change speeds on a VFD. One I’m using uses two push buttons for speed control. Yet another is self adjusting by monitoring the amps the motor is pulling.


How big is the motor? You can get smaller VFD’s that use 110v, for example


@shramiksalgaonkar what I mean by calibrate is how do I get the pi to translate the input it gets from the probe in to the correct temperature reading.

I do believe I have the fan speed taken care of. I bought a 12v DC blower and I am waiting for a digital potentiometer to operate a speed controller.


what I would suggest is to do your project using an Arduino device. Any specific reason why you are using a Raspberry Pi here?
For, k type thermocouple follow this tutorial and get reading from the chamber temperature sensor
Next, you will need an ethernet or wifi module for internet connection. Or a better option is nodemcu or wemos device.
Depending on the code in the tutorial:

float temp;   //declare a variable temp

temp = ktc.readCelsius();     // read the sensor reading and store in temp
Cayenne.celsiusWrite(1, temp);       //send the temp value to cayenne dashboard on channel 1

Once you have the temp value on the cayenne dashboard, you can use a trigger to turn ON/OFF your blower or code it in such a way that you can control the speed.