Put A Smoke Detector To Some Use

While we’re certainly not denying that smoke detectors are useful, there’s a certain kind of tragedy to the fact that most of them will never realize their true purpose of detecting smoke, and alerting us to a dangerous fire. On the other hand, [Ben] really unlocks the potential hidden deep in every smoke detector with his latest project which uses the smoke-detecting parts of a smoke detector to turn on the exhaust fan over his stove.

The project didn’t start with the noble aim of realizing the hidden and underutilized quiescent nature of a smoke alarm, though. He wanted his range exhaust fan to turn on automatically when it was needed during his (and his family’s) cooking activities. The particular range has four speeds so he wired up four relays to each of the switches in the range and programmed a Particle Photon to turn them on based on readings from an MQ-2 gas-detecting sensor.

The sensor didn’t work as well as he had hoped. It was overly sensitive to some gasses like LPG which would turn the range on full blast any time he used his cooking spray. Meanwhile, it would drift and not work properly during normal cooking. He tried disabling it and using only a temperature sensor, which didn’t work well either. Finally, he got the idea to tear apart a smoke detector and use its sensor’s analog output to inform the microcontroller of the current need for an exhaust fan. Now that that’s done, [Ben] might want to add some additional safety features to his stovetop too.

29 thoughts on “Put A Smoke Detector To Some Use

    1. Good point, especially since our kitchen gets quite a bit of use (certainly more than the ‘average’ American one at least). I’d considered other sensors but getting a reading on the actual smoke was key to really take advantage of the multi-speed fan. I also wanted it all to be hidden from view.

      If it dies eventually I might look at something else, or just buy another cheapo smoke alarm if it lasts long enough.

    2. A flame detector “should” not be a solution. Normally you do not want/have flames when cooking. Except when you use a gas range, then you have the fume extraction all the time when you cook. Not only when it is necessary.

    3. I would actually use two temperature sensors. One above the hood for room temperature reference and one at the hood. The temperature difference can be used to figure out the stove is on and different fan speeds.
      Smoke detectors or optic sensors could be clotted up over time during to grease.

  1. Situation: “The smoke detector sometimes goes off when I’m cooking.”
    Most people: “That’s really annoying.”
    This person: “You know what would be even better? Putting it closer to the food and making it more sensitive. Then it could detect every time I’m cooking.”

      1. Always amazes me when people can’t boil water without lighting the kitchen on fire. Or the need to replace the pan after every meal.

        I think it also works as a great warning for other things in life. Can’t boil water without a need to call the fire department. Well then, no drivers license for you.

      1. Yes it is called vegetable oil. It is just a spay one oil that makes it fast and easy to oil a pan. I find it funny how people from outside the US think they have a complete understanding of the US population of 327 million people just from TV, movies, and what they read on the internet.

        1. ^This.
          It’s simply vegetable oil in a convenient spray can. The largest name brand of it that I am aware of is “Pam”.
          I find it fascinating that despite the fact that all of us around the world grow up with different culture, brands, morals, beliefs, expectations, conditions, culture, and education, and yet so many of us seem utterly shocked that things in their little corner of the world aren’t how things are everywhere else.

    1. It’s not *just* oil, because the story says when it was used the detector reacted to LPG. That needs some explaining!

      Nothing wrong with a spray of oil – I use oil in a pump spray – that’s pure oil, no additives, I know because I fill it myself. It’s easier to use less than pouring from a bottle.

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