Flame sensor

I'm designing a burner control for my beer home brew system. I use a plc to control the pumping and will use it for flame ignition and safety also. I
all ready have the ignition parts and I'm looking for a flame safety device with a contact output. I know I could purchase a commercial flame safety relay but that is cost-prohibitive. Does anybody know how a gas clothes dryer flame sensor operates(eBay item 120335493311 at $9.95 is an example)and if it has a contact output? I could probably go to a HVAC contractor and find something in their junk pile but I was searching for a simpler and slightly more elegant solution than cannibalizing a furnace, another option is a flame rod, amp to convert mv to 5vdc and a relay. Or are their any other thoughts for a simple flame safety device with a contact output that is off the shelf and not high dollar.
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Flame sensor and a mv relay as in a gas fireplace. Chances of getting the combination at $10 may be low but chances of failure with a cheap replacement can be rather more costly
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Don Kelly snipped-for-privacy@shawcross.ca
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Not familiar with gas fireplace flame supervision. Are you referring to a complete unit or individual parts? Is the sensor a flame rod or thermocouple. Any leads on where to get a millivolt relay?

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mine is a "flame rod" (which is now apparently old technology ) but a thermocouple would work. Most gas fireplaces use millivolt relays- so they are independent of the grid. I suggest that you contact the gas fireplace vendors.
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Don Kelly snipped-for-privacy@shawcross.ca
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Maybe try an "old man Newson" device?
Kirk Johnson. "Stretching it wide since 1975!"
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No idea what an "old man Newson device" is ???

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Bit like an ol man Elvis boy.

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Your best bet is going to be to buy a flame supervision/igniter unit of the type used in gas appliances, as a spare part or a working part rescued from a scrapped appliance.
Ignition modules used in modern UK gas appliances are of the ionisation type -- an electrode in the flame detects the flame by conduction through the flame. This is often also the spark ignition electrode, although some use a separate detection electrode at the far end of the burner to ensure flame ignition has run the whole burner length. Some modules are intended to light the main burner directly, sometimes at reduced gas flow until flame is detected, and some are designed for two-stage ignition - a pilot flame first, and when ignition is detected the main burner gas valve is opened. On loss of flame, the gas valves are closed.
Note there may be legal requirements related to safety of gas appliances and installation in your area, which you should make yourself aware of.
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Andrew Gabriel
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Look at some of the ignition controllers made by Fenwal, available from HVAC suppliers, especially the models designed to be used in campers and other RVs. They have some fully functional ignition control units with built-in flame detection circuitry for well under $100. You can control power to the device to cause it to spark and use the valve control output as a contact output for ignition failure detection and control the valve yourself, or just use its built in functionality and let it control the gas valve etc. I would be very careful doing it yourself though, as it will almost certainly be against code/law in your locale, and may be unsafe since you are unlikely to think of all the "what-ifs" safety controls built into the certified products. Do a search for CSA B149.3 and NFPA 86 Section 5 for the applicable regulations. Also keep in mind that natural gas is usually heavier than air, so make sure the area around your burner is well vented and there are no wells or enclosed spaces nearby that can accumulate unsafe / explosive levels of unburnt gas.
TK
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