Unpacking an Old Smoke Detector

 I have been meaning to open this for a while now. This PCB came off an old smoke detector I found in a pile of electronic trash. A lot of these old smoke detector have two major enclosures inside the main unit. The one on the right houses the loudspeaker that plays a ~10kHz sound (also goes off for low battery. The one on the left houses an Am-241 button. The Am-241 releases a torrent of alpha particles into a metal plate. The metal plate is thus partially charged at any given time. If smoke enters the black enclosure, it attenuates the alpha particles at a much greater rate than normal air. The lack of alpha particles charging the metal plate causes the attached chip to send an alarm signal to the loudspeaker.

Hard to see here, sorry, but the small dark circle in the middle of the metal plate is an Am-241 button.

-

2 comments:

Subscribe to: Post Comments (Atom)

Resonant Shower Cavity and Aquarium in Monterey, CA

  Jellys in the tank I took a photo of Last night, I was humming in the shower of my cheap motel in Monterey. As I hit a low note in my litt...

  • Motivation Parallels
    Acoustics and looking at beam patterns I have my own temporary place during these hectic times. It's a one bedroom apartment on ...
  • Static Hosting with AWS
    I have been spending some of my spare time learning the ropes of Amazon Web Services (AWS). This service is great for handling large scale n...
  • Balloon Recovery Photos
     I plan to post some videos of the weather balloon flight in the coming days. The photos here show the tangled wires and molex on the insu...