I have a project where I have installed LED lighting above my gas range and I want to turn that light on and off as the gas is turned on and off. The simplest way I think I can detect this is to have a flow meter that would send a signal as it was turned on and off to Arduino that could then turn the lights on and off. Thoughts? I am open to any other way to accomplish this as I just want it to be cheap and easy if possible.
Thanks!
Don’t play with the gas supply !!
Why not look for heat rising .
You might want the light on before or after the gas is off during a cooking exercise .
Eg boiling milk , overflows , turn gas off , light goes off .
This is purely a visual thing the light is to show that gas is on or off. Something like this but for gas....
Ask your local gas installation specialist because it is better for you, your family and for the house.
If your device uses a pilot light, gas is ALWAYS flowing!
For mounting the flowmeter you would have to dismount the gas-pipe and insert the flow-meter.
This means you change the gas-installation.
This is what user @hammy means if he says
do you have a formal graduation for gas-installations?
I am pretty sure you don't have a formal graduation for gas-installations.
Can you write down all the special things that you have to take care of for gas-installations?
Do you have the equipment / the measuring devices for leak testing?
I am very sure you don't.
Changing a gas-installation without the knowledge how to do it right is dangerous.
If you have the attitude: " oh I know enough how to do it"
then it is ten times more dangerous because then you are a careless person!
Imagine this:
I am sure you have minimum one person that you like or love.
Imagine this person would die caused by a gas-explosion.
Is it worth the risk? No! never!!
How many unconvenient things would you do each and every day to get this person back to life again?
I am sure a lot of things.
This means it is not worth playing with the gas-installation.
don't use a flow-meter !
Describe in detail what the whole project is.
There is a high chance that detecting the gas-flow can be done in other ways that leave the gas-installation as it is.
Where does the gas flow to?
I am pretty sure the gas will be burned. This means there is heat that you can detect.
Even if you have 10 different places where the gas is flowing to. Using 10 sensors to detect heat will be still pretty cheap.
I am very sure that there is some kind of a measuring-device that measures how much gas has been burned.
Post a picture of how this gas-volume-measuring device is looking like
and then let's see what solutions can be found
best regards Stefan
Would a PIR pointed down at the stove top be useful? Or an IR camera?
Why?
As much as I like the off the wall projects, I have to join with the choir and say don't do this. Or at least if you do it, use a flammable gas-rated flowmeter and have the entire assembly installed and inspected by a certified technician. Who will, of course, refuse to sign off on it...
YIIIIIIKESSSS!!!!!!!....looks like you'l be on cloud nine anytime soon then....... 
Pull one of the knobs off and see if you can fit a tiny micro-switch or something similar.
I second the switch on the knob concept. Perhaps a photo interrupter that only passes light with the knob fully off. Put a small reflector on th knob that is over the sensor when the knobs are off. Unless you know what you’re doing gas plumbing would be ill-advised. And expensive either way. Flow meters/switches aren’t cheap.
Spot on . It is likely to be illegal for you to do this as well .
You won’t find a suitable flow meter in any case that is small
Not illegal for homeowners in most states. Massachusetts has laws against it though. You know, the state where the gas company burned down half the houses in Merrimack County.
Stefan I appreciate your thoughts. I will not be the one installing whatever I come up with I will use a professional so please do not be concerned in that regard. I had a pro install my gas when I moved it in the kitchen paid $800 for 30 minutes so....
Anyways its extremely simple
I have a stove that has natural gas.
I want to detect when the gas is on and stove is lit.
I would be OK with just knowing the gas is on or off.
I would prefer not to do heat detection as this is not as accurate.
Once the signal is sent I want to then turn the LED lights that I have put within my tile to turn on and off depending on the state of the gas. Right now I have a manual switch.
Hope this is clear. I would ask that people tell me what to do vs what to not do.
Thanks
As in states of the USA? 
But @ajstuart might be outside the USA ... 
It would certainly be illegal in the UK. 
See posts #11 and #12 ...
Hi @ajstuart,
ahh ! I understand. Nice picture of the stove.
Do I assume right that the blue and yellow light are the LEDs?
Please post a picture of the gasvalve.
Or do you want to detect when you opened one of the knobs with which you regulate the heat of the burners ?
Hm - if this is the case: is this stove the only device that is supplied with gas?
or
does the heating and warmwater burn gas too?
Is the piping from your gas-counter to the stove all the way hard soldered unsolvable metal pipe?
or
Is there somewhere inbetween a solvable connection with threads?
This might be a place for inserting a flow-meter.
Though a stove does consume only a medium flow of gas.
So the flowmeter should be rather small.
And - of course the flowmeter must be certified for use in a natural gas supply-pipe.
Another idea might be a pressure-sensor that is certified for natural gas.
I know the pressure in the pipe towards the burners is rather low. But there are pressure-sensors down to 10 Pascal.
Can you please post a pitcure how the knobs to open/close the gasflow look like?
Depending on the design maybe something different than measuring gasflow is possible to do
best regards Stefan
I couldn’t tell if you wanted the response to be instantaneous or not. If a slight delay is tolerable, you could put a thermocouple wire near each burner and monitor each one.
Image of typical thermocouple from gas range flame sensor that looks easy to mount,
I wonder if the the "stove" also has an oven that is heated with gas?
