I'm working on a arduino based temp controller for a propane kiln/furnace, and Im trying to find an alternate way to sense wether the burner has a lit flame or not.
The IR flame sensing modules won't work, unless someone has any ideas for alternate mounting, as the burner inlet is in a closed space where temps are way too high(>2300f) for the sensor to withstand.
I have a type k thermocouple to measure temp, but it won't tell me if the burner is actually lit or not because the insulation hold heat too well for a change in temp to signal that the burner is not lit.
Does anyone have any suggestions for a high temp flame sensor, or anyway to mount the standard modules so that they wouldn't be melted by the radiant heat?
Your propane kiln/furnace must have a vent at the bottom for the combustion air to enter. This area cannot be as hot as you suggest. Can you sensor go in this area?
You can also use a glass rod going through the wall of the kiln, into a relatively cool area and put the sensor on the other end of the rod.
You can also put a metal mirror inside the kiln and let the sensor see the flame reflection off the mirror.
Is that any help?
Paul
Note - a flame will conduct electricity...
Why not use a standard thermocouple kind of probe that home furnaces use? Pick one up at Home Depot, sits if the flame of the pilot light 24/7 and lets the controller know it save to turn the gas on full.
http://www.homedepot.com/ search thermocouple.
They last 2-3 years, always seem to go bad in the middle of the coldest night in February! I keep a couple spares on hand.
Might work by simple metallix expansion - probe gets hot, other end gets pushed out.
Paul: the air for combustion is drawn into the burner outside the furnace(the whole burner is outside the furnace).
I will need to add an exhaust port to my design but because of the way the burner sits, the flame is partially concealed for easy view. Plus the exhaust will be on top, to allow burnout fumes to escape(from wax burnout for casting).
In doing more google searching, there seems to be something called a flame rod. It uses a metal rod(kinda like a thermocouple) and it runs an AC current that will be affected by a flame, if present, or not.
They seem to be available as integral with the ignition electrodes used to light burners, but how to interface with an arduino is beyond me.
I know this is an old thread but since it popped up on google, I will go ahead and post my solution for this particular challenge. My requirement was very similar, I was using a torch apparatus to heat my DIY forge for use in some metal tempering. my solution was to add a 90 brass adapter to the propane tube placing it behind the air intake for the torch head then drilled a hole in the bend of the adapter in such a way the if i had a longer drill, it would have gone right thru the vortex and out the front of the torch. I mounted the sensor with photo transistor aimed down the gas pipe looking at the flame from the backside. I used a small ceramic insert to protect led from direct contact with the brass. Its far enough away from the flame as to avoid damage .