flame sensor

[seayaker]

I need to make this flame sensor open the solenoid which lets the gas flow to the burner, so If the flame goes out the gas will shut off. If I connect a 3v battery to the solenoid it will open and the gas will flow, my meter says it draws 0.22 amps, The flame sensor puts out a very slight signal so I got this - AD620 Mirco Milli Volt Signal Amplifier.

I have it connected to a 12 v battery. When I hold a lighter so the flame touches both the burner which is connected to ground and the flame sensor which is connected to the + output I can get it to read 3v briefly. When I touch the burner and sensor with my finger it will stay at 3v but will not output enough power to open the solenoid. What do I need to do to get it to open when I apply a flame?

 

[Eufalconimorph]

Which flame sensor? Link the datasheet, there are too many different types with entirely different operating principles to know anything from just "flame sensor". Likewise for the solenoid. Do you have a circuit diagram? It's difficult to follow what's connected where from your description. The AD620 IC is an instrumentation amplifier, it can't drive a solenoid directly, 220mA is a lot higher than the 7.5mA the datasheet specifies for all the typical operating characteristics.

 

[waross]

Why not use an off the shelf furnace or hot water tank gas controller.
Flame sensing is done by a thermo-couple which puts out enough current to hold the valve open.
Don't re-invent the wheel.

 

[danw2]

flame sensing is a safety circuit that is used to prove flame and has to fail safe. Commercial products pass agency approval. Buy commercial flame sensing/safety components.

 

[seayaker]

Why not use an off the shelf furnace or hot water tank gas controller.
Flame sensing is done by a thermo-couple which puts out enough current to hold the valve open.
Don't re-invent the wheel.

I was going to do that first then someone said all I need is this AD620 IC. The furnace controllers have several other switches I'd have to bypass somehow. They have a purge fan and a flag switch and maybe something else. All this is for is so if the flame goes out the gas shuts off. It will be outside and lite manually. If you know how to make make something like this work please let me know.

31501 RV Furnace Ignition Control Circuit Board For Atwood & Dometic 33488 33727

 

[MintJulep]

Don't reinvent the wheel.

https://www.eng-tips.com/threads/more-about-gas-fired-home-appliances.206868/

 

[3DDave]

Pat's Pub link?

 

[LionelHutz]

Use a gas valve with a thermocouple.

 

[seayaker]

I considered that, the burner is already set up for the flame rod, the solenoid works fine if I could get the sensor rod to control it. Wouldn't that be safer, more reliable? I have to be able to turn the gas on to light it, will the thermocouple open if I hold a lighter to it? In my search for a solution I found several other people trying to do the same thing. Apparently no one makes a module without the igniter. I took the one apart the one that was on the burner (it was fried). It had 3 flame rods connected, I believe one was the igniter and the other 2 were the flame sensors. They were both connected to the inductor. someone posted that it probably had two sets of probes polarized in opposite directions. Subtract one signal from the other and calibrate the difference for flame vs no flame). I believe that's how it worked. If you have any knowledge of this please let me know.

 

[3DDave]

See https://www.pjrc.com/pilot-light-flame-sensor-for-burning-man-art/

 

[seayaker]

Thanks, I saw that. I don't have the tools or experience to try something like that and make it trustworthy. I'm trying to find out if I can bypass the igniter and use the flame sensor part of this board.

 

[waross]

There are approved industrial flame sensor boards that sense a flame and give an output.
You do the ignition, manual or automatic, and control the pilot valve and the main valve.
There were many furnace and hot water tank, gas control valves with manual lighting.

 

[seayaker]

There are approved industrial flame sensor boards that sense a flame and give an output.
You do the ignition, manual or automatic, and control the pilot valve and the main valve.
There were many furnace and hot water tank, gas control valves with manual lighting

There are approved industrial flame sensor boards that sense a flame and give an output.
You do the ignition, manual or automatic, and control the pilot valve and the main valve.
There were many furnace and hot water tank, gas control valves with manual lighting.

Great where do I get one?

 

[3DDave]

The other source of the OPs information: https://forum.allaboutcircuits.com/threads/flame-sensor-circuit.205328/ to review before making any other replies.