I'm building a system using a microcontroller (like an Arduino maybe) to automatically control the temperature of a kettle of liquid being heated by an LP gas burner with a PID algorithm to turn the burner on and off.
I'm having difficulty figuring out how to sense presence/absence of the flame so I can deactivate the igniter and then monitor for flame blowout. I looked at flame sensor rods as used in furnaces (rectifier type), but can't find anything on how to interface one to the microcontroller.
I considered using a thermopile, but they seem to be used mostly for pilot flame, so I'm not sure if would work for the main flame. I looked at a fire sensor (transistor based) for the Arduino, but it doesn't detect natural gas flame, so I'm not sure if would work for LP.
I need a solution.
Safety is not a big concern since this will never be used indoors, and will always be monitored constantly while in operation. A common approach for this is to manually ignite the burner and monitor a thermometer in the liquid. The burners are periodically adjusted using a ball valve. I'd just like to make the process a little easier, but have no intention of leaving it unattended. So I guess you could say that adding a
flame detector is just a secondary extra safety measure.
Thanks everyone for your input. I've began analyzing an electric alternative. I'll need to go 220V with around 5500W elements in the liquid, but it is definitely doable. I can use a SSR to feed the power and regulate the temperature. It's definitely a cleaner and simpler alternative, so I may go that way. Thanks again for being so responsive.
Now, I need to finalize on the microcontroller selection. I'm thinking maybe an Atmel. I see there are some opinions already posted on this. Anyone have specific suggestions on models, and rational for the proposed selection?