Starting a gass burner using an ignitor?

[kchaloup]

I'm trying to design a circut to start a gas burner by using an solid state ignitor like the ones used in BBQ grills or gas stove tops. I've found some ICs made by STM designed for fire ignition circuits. The question that I have is once the fire has been started how can you detect it so that you disable the ignition circuit? I've noticed on some gas stove top no additional sensors are used other than the ignitor itself.

 

[geo57]

In industrial applications this is usally done using flame scanners which detect UV, IR, or both. Your home hot water heater (if it's gas) uses a thermocouple assembly. This would most likely be your best bet, if you are designing some type of electronic system. It would fairly easy to add the thermocouple circuitry. George Griggs
Sr Process Controls Engineer

 

[busbar]

Not sure of its specific electrical characteristic, but in US’ consumer-grade natural-gas-fired equipment for the last couple of decades, it appears that something is sensed by nothing other than across the ignitor spark gap.

 

[Lewish]

I don't know if this helps, but my gas furnace, which heats my house, has a UV detector to detect the flame and turn the ignitor off. It is controlled by a PIC processor.
As a side note, all burning hydro-carbons emit UV when adequate oxygen is present. That is why oxy-gas welders wear goggles.

 

[purplepete]

I'm not sure if they're still used but a long time ago we used the conductivity of the flame as a means of flame detection in igniters (for small systems).
One electrode sat into the flame area, sometimes you'd need to "ground" the base of the flame to ensure conductivity. A solid-state relay was switched on when current passed through the ionised flame.

 

[buzzp]

If the igniter is the only device close to the flame. Then there is usually a third conductor of which a current is induced when there is flame. This current is measured to verify there is flame present. (the ones I am used to are 1-2uA)Other devices may use a Cadmium cell like honeywell, C554A. These are essentially 'eyes' that will change resistance based on the light (wont work well unless there is next to no light within the burner assembly-probably not the case with a gas stove). There are a variety of other components that you can use as well.
I do not believe there was any flame detection on gas stoves since there is limited amount of fuel coming through the pilot valve.
My experience is with diesel fired burners and propane.

 

[TravisWolfe]

Another name of a type of flame sensor is a Flame Rod. Essentially the same as the gentleman above commented on, that when there is a flame there is ionization present which induces a current in the rod and hence senses flame. The current is fairly low...around 2 microamps or so.

 

[jbartos]

Suggestion: Visit
thread237-31888

http://www.epinions.com/content_61891055236

http://www.tssa.org/fuels/pdf/october_2001_gas.pdf

(for safety)

http://www.southbendnc.com/manuals/combi.pdf

(for Combi)
etc. for more info