Proximity Sensor Recommendation Fire Pit

[Dogman]

I am installing a new Copper fire pit and the gas control is an electrically operated 24v valve similar to gas fireplace. I want to be able to put a cover on the Fire Pit when it is not in use just to keep debris and rain out of it. However, I want to put in an interlock so that if somebody (Wife) doesn't pay attention and remove the cover first she won't accidently turn it on and heat up the Copper cover. So I could use a simple magnet contact and connect it as an input zone on my M1 but using a magnetic contact would mean the cover would have to be perfectly positioned and so I would rather just use a proximity sensor of some sort to detect that the cover is installed. Does anyone have any good suggestions or sources for a small prox sensor that can be used outside and is relatively robust?

 

[Vycor]

Hmm not sure... circular prox sensor... i like the idea, i do but to keep it "idiot proof" is tricky...

my thoughts... make the cover ONLY fit on a certain way... maybe a notch or something to force it... what about if someones knocks it off, the wind/dog/kids/landscaper? then your gas valve is on... when your gas valve is on, is it pumping out as or its just opened, ready for you to open it manually? its a neat idea but im just worried about the security of it, now you basically have a potential open gas valve that can get triggered by something falling off.

also, whats the magnetic contact doing again, detecting if its on or not right? what will that solve? the cover will be OFF when in use so your contact wont work.

heres my thought... put the contact somewhere near it that REQUIRES the lit to be placed on it, now thats a better security option. no gas until that lid is in the right spot... sort like a KEY in order to get any gas...

 

[SteveQ]

If the cover is light tight, you could put a dusk/dawn sensor inside the lid, or perhaps a motion sensor! It should trigger when the lid is removed. That trigger would then satisfy one of the conditions that would allow the fireplace to ignite.

Steve Q

 

[Vycor]

If the cover is light tight, you could put a dusk/dawn sensor inside the lid, or perhaps a motion sensor! It should trigger when the lid is removed. That trigger would then satisfy one of the conditions that would allow the fireplace to ignite.

Steve Q

LOL, but doesnt a dusk/dawn sensor detect when its dark. If its dark in the lid, it'll be triggered (its closed)... when he takes it off... umm its gonna be dark out still, at least whenever i light fires its dark out... sooo it'll still think (its closed)

 

[potts.mike]

The way I read it he wants the fire not to turn on when the lid is on. If your willing to put a sensor in the lid then an ultrasonic rangefinder might work. Depending on how the pit is designed you could maybe put a pressure transducer under one of the legs. I think magnetic is probably your best bet though. Maybe use more than one to get decent coverage.

 

[pete_c]

One thing for sure for whatever you use or if you use the base is to make sure it doesn't melt.

 

[Dogman]

One thing for sure for whatever you use or if you use the base is to make sure it doesn't melt.

I do plan on using a cover that is also copper so even if it does ignite then there will not be a melted mess at least unless it is on awhile. I thought about the optical sensor but as someone pointed out I plan on using the firepit at night so that is not the best approach. I also thought about indexing the cover so it only fits on one way but I would rather not do that unless there is no other option that is why I was thinking about a Hall Effect prox sensor if it would work in my case. I was hoping someone might have some experience with these to see if I can make one work.

I forgot to mention that the gas valve is also a combination ignitor with a thermo couple so if it were to inadvertently turn on it would not just spew gas it would ignite the fire ring as well and if it can't ignite the fire ring then it does shut off the gas. The ultrasonic rangefinger is an interesting thought so maybe I will check that out but I still think some sort of prox sensor would be my best bet.

 

[rbroders]

How about a simple pressure switch. When the cover is on it pushes down the switch and breaks the contact. Keep it away from the flames, of course. I like this switch because it is sealed: Sealed Limit Switch

Also, I think I would skip the Elk, just wire the ignitor circuit directly through the switch. One less thing to go wrong.

--Bob

P.S. I also like the idea of using a 120V timer on the fireplace switch. Thus you can't leave it on all night long by mistake. You could turn on the timer, and then when removing the cover, the fire would "magically" light...

 

[Rupp]

Which fire pit did you purchase? I'm looking and have looked forever tring to find one that I like.

 

[IndyMike]

I use the following on my deadbolts to verify that they are thrown. They're available in PNP and NPN outputs. With a little resistor programming, they interface to the ELK nicely.

http://www.automationdirect.com/static/spe...roxrectaps4.pdf

These use a "tuned coil" that detects the presence of ferrous metals (shifts the coil frequency). I've tried them with a variety of metals, but not copper. If you're interested, I can try a test.

There are a number of different form factors and bodies available at automation direct (metal bodies as well). I have not tried the other products.