Beefing up a smoke alarm system with video, temperature, and connectivity

Here’s a little smoke detector hack which [Ivan] has been working on. He wanted to extend the functionality of a standard detector and we’re happy to see that he’s doing it with as little alteration to the original equipment as possible (this is a life-saving device after all). He sent all the build images for the project to our tips line. You’ll find the assembly photos and schematic in the gallery after the break.

As you can see his entry point is the piezo element which generates the shrill sound when smoke as been detected. He connected this to his own hardware using an optoisolator. This allows him to monitor the state of the smoke alarm on his server. It then takes over, providing a webpage that display’s the board’s temperature sensor value and streams video from an infrared camera.

Of course this is of limited value. We’ve always made sure that our home was equipped with smoke detectors but the only time they’ve ever gone off was from normal cooking smoke or after an extremely steamy shower. But still, it’s a fun project to learn from and we’ve actually got several of the older 9V battery type of detectors sitting in our junk bin.

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Leaking water detector from an old smoke alarm

[Thomas Clauser] had his basement flood last year when a hurricane swept over New England. The problem with flooding or leaking water is that chances are you won’t notice until it’s too late. He decided to protect against this in the future by building his own leaking water detector. It’s a simple device that sits on the floor of his basement and triggers an audio alarm if water begins to cover the floor.

He used an old smoke detector for the build; a nice choice since it’s loud, and designed for long-term battery operation. It also has a button for testing if the detector is working. [Thomas] removed the PCB from the smoke detector case and soldered wires onto the test button contacts. He cut a sponge to squeeze it inside of a PVC pipe connector housing. That sits against the floor, with the wires for the test button contacts placed through the sponge. If water is soaked up by the sponge it completes the circuit and triggers the alarm.

A few other design features really make this a nice setup. He notched out the bottom of the PVC connector so that water can flow freely, and added a switch to one of the probe wires lets him kill the alarm when inspecting the damage.

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