Plasma ConductanceCool Fact - flame is a plasma and will conduct current. I tried using two wires stuck into the flame. The flame has a fair amount of resistance. One of the wires was connected to 5V. The other was connected to a voltmeter. There were dozens of mV present when the flame was on and zero when it was not.
I think this could be used with an analog input as a flame sensor.
|100X Amplification Circuit for Thermocouple|
|Digital IR Flame Detector|
IR Flame DetectorSensors are available that detect the IR signature of a flame. Most of these provide analog output only, but I found some that also include a digital output. This is provided by a built in level compare circuit with an adjustable level. Because this method is so simple to interface with, this is what I decided to use. One big problem quickly became apparent - the sensor is triggered by incandescent lights and sunlight. It worked fine under florescent lights.
I was successful in using this configuration for brewing. The IR sensor works, but has the false trigger problem. It works for me but won't work in many environments. My plan is to rebuild the brewing interface with analog input capability and try one of the other methods.
|IR sensor mounted on a small block of wood and placed under the flame.|