The Heater in the workshop had been playing up and the automatic switch on/off off the blower fan had stopped working.
Taking the heater apart the fault could be seen that the capillary tube was leaking, this sticks into the heater and when warm enough pushes and mechanical switch and turns the blower on, after a lot off searching we found the part is no longer available and was over £120 last time you could buy it.
Time to replace new for old, I have a arduino (open source prototyping electronic devlopment board) this can be used to read and control various hardware, I also ordered a thermocouple and relay board. With all the parts here the first thing was to fit test the thermocouple with this wired to the board and small sketch to read the current temperature with this working correctly the next stage was to fit the thermocouple into the heater, with the heater ready and sketch running we did and test run on the heater this gave a graph off how the heater warmed up.
Red line= Heater burner on/off – Green line= Blower on/off (Manually switch on/off)
This gave me the on/off temperatures needed to switch the blower on and off, Back to the software writing and using a Average system this takes 10 temp (2 per second) readings and outputs an average reading which is used to operate the relay board (this stops any quick on/off’s). With the system working on the arduino board I then changed over to a cheaper Xino basic board but used the main microprocessor from the arduino with the written software on it.
With this all fitted in a protective plastic case we now have a working full automatic heater again.