A Cheap DIY Smoke Detector That Can Save Lives

2014-07-19-16.33.53 A faulty wire, a discarded burning cigarette, or a left-on curling iron can trigger sparks of fire to engulf everything nearby until all that’s left is brittle mounds of smoldering ash. Which is why smoke detectors are so important. They are life saving devices that can wake people up sleeping inside, well before the silent, but deadly carbon monoxide starts to kick in. But what happens if no one is home, and the alarm begins to blare? The place burns down into the ground without the owners knowing.

So when [Martin] purchased a battery-powered smoke detector and rigged it up to notify him exactly when the piezo siren is activated, the evolution of the automatic fire alarm continued into the realm of wireless internet-connected things.

His home automation system (a Raspberry Pi running Node-Red) links to a Funky ATTiny84-based sensor and transmits the data wirelessly, redirecting the information to his phone. SMS messages can be sent, as well as emails and pushbullet notifications. Once the piezo siren starts to sing, the system alerts him that smoke has been detected and that he should check on it as soon as possible.

The electronics fit perfectly inside the case waiting for any smoky disturbance in the room to light up. And what makes this project even better, besides the life saving capabilities and the instant push notifications, is that it was hooked up for the cheap. No need to buy a brand-new, expensive Nest protect, when all it takes it a sensor or two and a Raspberry Pi to hack the fire alarm that already sits in the house.

This video coming up after the break shows how simple it is to make.

For more projects similar to this, check out this leaking water detector developed from an old smoke alarm, and this beefed-up fire detector with built in video, temperature, and internet connectivity. You might also like this very tiny gamma radiation detector that uses a very small photodiode and a miniature solar cell as well.

25 thoughts on “A Cheap DIY Smoke Detector That Can Save Lives

  1. I don’t want to be the guy bashing the project, but what would be the use of your smoke detector warning you if you’re out of the house? Did you develop firefighter skills in the mere seconds you realized what was happening?
    If no one is home, consider yourself lucky. Please be safe. :-)
    (in before “because he can” and “not fun if safe” crowd)

    Otherwise the project seems well done, although it would be expected.

      1. I can see a Web 2.0 app/site, where neighbours respond to your internet connected smoke alarm, because you sign up to respond to their alarms.

        Better hope that it isn’t the power adapter for the router or Raspberry Pi that is on fire!

    1. While I agree if your out when the smoke alarm goes off your laughing, but the article says he has home automation and if his system has cameras then he could check to see if its a real fire he can call 911 to have the Firemen put the wet stuff on the red stuff.

  2. The new mains connected smokies also have an interconnect terminal, so that if one goes into alarm, all the connected ones also go into alarm. The interconnect does not run at mains (at least on the ones I have installed), so it shouldn’t be to hard to rig a notification without having to bust open the unit.

    1. Might even have that cable in the basement if it’s a newer home. I had asked about that when we moved into our new house- there was a patch panel in the basement with a bundle of wires next to it, one of which had a cap on it. I asked what made that particular wire so important and was informed that it was connected to the forth wire on all the detectors, which the units used to signal each other and also the home alarm system.

  3. There are 3 wire smoke alarms that {obviously may cost more} that have an “interconnect” wire to gang the alarms together. This would also seem to be an off the shelf way to integrate the whole deal into a security system or{the interwubs}.

  4. Some sidebars:

    The primary object of a smoke alarm is to save the lives of people within the building.

    Here in Australia smoke alarms are typically audible in the house next door, and I certainly know every time the women at the far end of the block of flats burns her toast.

    The sound level required by AS 1670.1 [5] is 75dB of ~3100 Hz “at the pillow”. Most alarms claim 120dB or more at 1m range. There is a strong argument for reducing the alarm tone to 520 Hz but this presents difficulty obtaining the required SPL.

    Just a little point, carbon-monoxide is actually the least of your worries with the smoke from a fire in the home – it’s the almost instant knock-down effect of a good whiff of Hydrogen cyanide.

    “The most common cause of death in fires is the inhalation of noxious gases rather than thermal injury. Hydrogen cyanide gas, the most toxic product of combustion, seldom is recognized as a significant hazard in smoke inhalation. … Sources of cyanide toxicity include the increased use of synthetic polymers in building materials and furnishings.”

  5. I picked up some 433Mhz smoke alarms (and door/window sensors, PIRs etc) dirt cheap on eBay and hooked them up to a jeenode (essentially arduino/atmega) plugged into raspberry pi running home automation software domotiga – few notes dotted around my blog http://tickett.wordpress.com/2013/11/08/further-433mhz-rf-hacking/
    jeenodes are also responsible for reading hot water/cold water/gas consumption and a bunch of environment bits- really must finish off the project sometime

  6. I wouldn’t want to directly modify a smoke detector as it is a piece of fire and safety equipment. i.e. liability, legal and insurance reason. These devices are certified, your mods decertified it.

    While easy for modding, doesn’t mean the noobs on the interweb that read this won’t screw up and DYI (Do yourself In).

    Smoke detectors are loud and have fixed frequency. It would be trivial to have a mic pick up right next to it. Piezo buzzer assembly from a dead one could be used as a mic as its resonance frequency would match and give you a high output. With a little of amplification, you can drive the rest of the your circuit.

    1. That is a very good point.

      Both ionic and optical smoke detectors are very finely tuned and can cause both false positives and false negatives from very small alterations.

      Even if you manage to make a connection filter that doesn’t alter the function you might make a cold solder or other damage to the alarm board. The only mod i would recommend is maybe a battery voltage monitor to make sure the alarm is operating, this could be made by patching into the battery compartment without harming the electronics board, just make sure the modded battery connection really connects to the smoke alarm…

      1. Most smoke detectors will give off a quick chirp when the battery is dying. If you do the acoustic coupling method of monitoring it, you could set up to monitor for this quick chirp as well, and have that send a notification of the low battery.

        1. Yes, but what if your battery was to die immediately (it happens), or you accidentally inserted a dead battery?

          Battery monitoring would also give you a chance to plan the battery change beyond waking up at 03:30 the day before an exam because the smoke detector is beeping…

          This is also irrelevant because i only mentioned battery monitoring as the only electrical mod i would recommend for a smoke alarm, i never said i recommended doing it, if you understand what i mean…

    2. Not only would your mods de-certify it, having a modified unit such as this as your primary smoke detector would likely void your homeowner’s insurance in many countries (the ins co’s look for any possible out they can find, and “tampering” with vital safety equipment would certainly be an out that they would seize upon). That said, I do like the idea of this project.

      I’d suggest having the required number of normal smoke detectors for your dwelling, and then adding some of these modded ones to their own separate circuit… don’t interface at all with the regular ones, leave them be. Then you’re covered (by the normal ones), but you’re still connected (by the extra/aux ones). Sure, it’s an extra battery or two to replace each year, but that’s a small price to pay for leaving your homeowner’s insurance policy intact.

    3. ^ this ^ – whatever certifying entities gave their blessing on the original unit are now null and void. the impact of that event on any insurance coverage could be quite bad.

      I don’t understand why he just doesn’t get a ‘centrally monitored’ alarm system. My home has multiple smoke, CO, security sensors – all connected to a 24×7 monitoring network. If anything trips I get notified… if I ignore it, the Fire Dept (and PD) show up at the front door anyway.

      1. Hmm, how about Price? The one you mention IS VERY VERY EXPENSIVE and can’t do really that much, the configurability is really lousy. I don’t own the house I live in. I rent, so I can’t really modify or do anything to the existing smoke alarms. They also are not connected, they are just simple units, so when a fire starts, and nobody is home, they will make a racket, till they melt from the fire and are more useless than an inflatable dart board. With the Raspberry Pi and an extra smoke alarm, the alarm will notify me, no matter where on earth I might be at that moment and I can check for real smoke via the camera that the raspberry pi has. Cheaper impossible, also no false alarms that get the fire department in motion and make you bill you for their useless intervention.

  7. IMO, it would be far easier to put a used smartphone somewhere in the house to monitor the distinct high-pinch noise of a smoke alarm. No risk of damaging the smoke detector.

  8. I have the same smoke detector at home. I’m really sorry if i ask u a silly question hahaha where is I’m not really known about the smoke detector circuit.I want to make iot smoke detector project so i need to connect smoke detector with Nodemcu-esp8266.So do i need to connect nodemcu with sensing chamber or just connect it to the buzzer, if I need which pin do I need to use?

  9. I have the same exact one but they cheaped out by using a 8 pin chip microcontroller versus a 16 pin chip that did the job!

    I really like the design of it, just displeased when they cheaped out on it.

    It doesn’t do a main important function: Warn of a LOW BATTERY! Even worse the circuit drains the battery in about 2 months! Which is terrible!

    i am wondering what i should do to get it to work like it should? Contact a smoke alarm manufacturer (like Kidde,First Alert) and ask if they can make a working circuit board for it OR just man up and use a name brand smoke alarm?
    What do you guys think?

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