Author Topic: Reverse engineering a big old American smoke detector  (Read 1752 times)

Offline klugesmith

  • High Voltage Engineer
  • ****
  • Posts: 361
  • Karma: +11/-0
    • View Profile
Reverse engineering a big old American smoke detector
« on: March 15, 2020, 09:50:48 PM »
Just noticed the thread about big old Soviet smoke detector, which makes this one seem as safe as baby ducklings.  Told this story yesterday, in almost the same words, on another forum.

Here is an old stock Pyrotronics F5B smoke detector head, similar to the F3/5 head. They are still available for people maintaining old installations, but typically cost well over $100 on ebay.

Ionization-type smoke detectors seem to have started in the 1960's. Preventing fires in industrial & institutional settings easily justified the proliferation of 80 microcurie Am-241 alpha particle sources. Those produce enough air ionization that a cold cathode trigger tube can switch the alarm circuit.

I got the pictured device to turn on a neon lamp, within a few seconds of being exposed to smoke from a smoldering popsicle stick. My circuit is shown below, on the right. The original application uses Base Units (sockets) with resistors and a neon indicator lamp, and if any reader has one I'd love to know the circuit details.

.
These old smoke detectors, just like modern ones with less than 1 uCi of radioisotope, use a reference ionization chamber as the high impedance on top of voltage divider. Cheaper than a many-gigaohm resistor, and it automatically compensates for pressure and temperature and decay of the alpha particle source.

I found out that the internal construction is similar to this unfinished drawing.  The ion chambers in schematic above were rendered accordingly.


It came as a surprise that the larger ionization source, which irradiates the smoky chamber, is directly visible through the window-screened ports. Close enough that energetic alpha particles, not just ions, could be escaping from the enclosure. Let's check with some alpha-viewing fluorescent film, like what's sold for making spinthariscopes.


Set shutter time to 30 s, aperture f/1.4, ISO 12800. Lights off, not completely. Go...


This device could be disassembled without any screwdriving, wrenching, or cutting. 
Not sure if that's a good idea, or a thing to talk about.
Even if it were reassembled and tested as a working smoke detector, good as new, ready to protect lives.

Offline John123

  • High Voltage Engineer
  • ****
  • Posts: 223
  • Karma: +4/-0
  • All the gear, no idea. UK
    • View Profile
Re: Reverse engineering a big old American smoke detector
« Reply #1 on: March 16, 2020, 05:57:16 AM »
Looks quite big in the photo compared to the ones inside modern detectors.

How come they were designed as replaceable parts, do they wear out and become unreliable over time?

Offline johnf

  • High Voltage Technician
  • ***
  • Posts: 156
  • Karma: +5/-0
    • View Profile
Re: Reverse engineering a big old American smoke detector
« Reply #2 on: March 18, 2020, 07:34:09 PM »
I think the part has been made much like tubes were made
in fact that looks like a standard octal tube base with a few pins missing.
this would fit well with early electronics manufacture allowing all to be tested before the detector head was put in

Offline TheMaxii2007

  • High Voltage Enthusiast
  • *
  • Posts: 3
  • Karma: +0/-0
    • View Profile
Re: Reverse engineering a big old American smoke detector
« Reply #3 on: June 02, 2020, 04:19:02 AM »
Hello My old smoke detector Am-241 (72 microcurie )  ;)






« Last Edit: June 02, 2020, 04:32:01 AM by TheMaxii2007 »

Offline klugesmith

  • High Voltage Engineer
  • ****
  • Posts: 361
  • Karma: +11/-0
    • View Profile
Re: Reverse engineering a big old American smoke detector
« Reply #4 on: June 04, 2020, 06:30:09 AM »
Welcome to the forum, and thank you for the interesting report.

The sectional drawing you shared is much better than anything I've seen before.
It sure beats measuring parts and drawing things from scratch.
Does the document it came from include details of the circuit in base unit?

Is there a model number and/or date code on your device? 
How come the nominal activity is 72 uCi, vs 80 uCi in my specimens and in the F3/5 model we can read about?

Might as well share a picture I made with alpha-viewing film, to get an idea of relative activity in the outer and inner chamber irradiators, next to a modern sub-1-uCi source.
« Last Edit: June 04, 2020, 06:49:45 AM by klugesmith »

Offline TheMaxii2007

  • High Voltage Enthusiast
  • *
  • Posts: 3
  • Karma: +0/-0
    • View Profile

High Voltage Forum

Re: Reverse engineering a big old American smoke detector
« Reply #5 on: June 06, 2020, 10:44:15 PM »

 


* Recent Topics and Posts

post Re: Capacitor Bank Series-Parallel Configuration
[Capacitor Banks]
klugesmith
Today at 03:51:26 AM
post Re: Primary Frequency too High
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
Today at 01:27:18 AM
post Re: Primary Frequency too High
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
Today at 01:19:19 AM
post Re: Syntherrupter - A Feature-rich, Polyphonic Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
SimonNwardUK
April 22, 2021, 10:36:43 PM
post Primary Frequency too High
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
April 22, 2021, 06:52:48 PM
post Re: Capacitor Bank Series-Parallel Configuration
[Capacitor Banks]
MrScrOggs
April 22, 2021, 01:20:02 PM
post Re: Corona discharge
[General Chat]
Uspring
April 22, 2021, 12:57:35 PM
post Re: B64290l0048x830 core for gate drive Help
[Dual Resonant Solid State Tesla coils (DRSSTC)]
GrantV
April 22, 2021, 10:59:28 AM
post Re: B64290l0048x830 core for gate drive Help
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
April 22, 2021, 05:56:48 AM
post Re: Capacitor Bank Series-Parallel Configuration
[Capacitor Banks]
MRMILSTAR
April 22, 2021, 05:38:10 AM
post Re: UD2.7 Thru Hole
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
April 22, 2021, 02:41:13 AM
post Re: Capacitor Bank Series-Parallel Configuration
[Capacitor Banks]
MrScrOggs
April 22, 2021, 02:41:08 AM
post B64290l0048x830 core for gate drive Help
[Dual Resonant Solid State Tesla coils (DRSSTC)]
thedoc298
April 21, 2021, 09:18:14 PM
post Re: Capacitor Bank Series-Parallel Configuration
[Capacitor Banks]
MRMILSTAR
April 21, 2021, 08:38:20 PM
post Re: MidiStick Polyphonic USB Midi Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Mads Barnkob
April 21, 2021, 08:15:13 PM
post Re: UD2.7 Thru Hole
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
April 21, 2021, 08:08:15 PM
post Re: Corona discharge
[General Chat]
Mads Barnkob
April 21, 2021, 07:59:41 PM
post Re: Capacitor Bank Series-Parallel Configuration
[Capacitor Banks]
Mads Barnkob
April 21, 2021, 07:40:40 PM
post Capacitor Bank Series-Parallel Configuration
[Capacitor Banks]
MrScrOggs
April 21, 2021, 04:29:42 PM
post Re: gdt high frequency ring
[Solid State Tesla Coils (SSTC)]
davekni
April 21, 2021, 06:12:33 AM
post UD2.7 Thru Hole
[Dual Resonant Solid State Tesla coils (DRSSTC)]
alan sailer
April 21, 2021, 03:52:44 AM
post Corona discharge
[General Chat]
T3sl4co1l
April 21, 2021, 12:16:22 AM
post Re: Mains Fullwave CWDRSSTC
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Vdekje
April 20, 2021, 10:48:45 PM
post Re: Welcome new members, come say hello and tell a little about yourself :)
[General Chat]
Vdekje
April 20, 2021, 10:33:53 PM
post Re: Project: FreakyDRSSTC MK1
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
April 20, 2021, 07:32:37 PM
post Re: gdt high frequency ring
[Solid State Tesla Coils (SSTC)]
balazs
April 20, 2021, 07:29:04 PM
post Re: Some questions about DRSSTC's, and guidance to build one.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
April 20, 2021, 07:25:30 PM
post Re: What driver to use for first DRSSTC build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
April 20, 2021, 06:55:36 PM
post Re: What driver to use for first DRSSTC build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
thedoc298
April 20, 2021, 06:48:29 PM
post Re: What driver to use for first DRSSTC build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
futurist
April 20, 2021, 03:42:58 PM
post Re: Some questions about DRSSTC's, and guidance to build one.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
mrsebe
April 20, 2021, 01:54:01 PM
post Re: MidiStick Polyphonic USB Midi Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
TMaxElectronics
April 20, 2021, 04:53:09 AM
post Re: Project: FreakyDRSSTC MK1
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
April 20, 2021, 02:32:21 AM
post Re: gdt high frequency ring
[Solid State Tesla Coils (SSTC)]
davekni
April 20, 2021, 02:28:12 AM
post Re: Some questions about DRSSTC's, and guidance to build one.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
April 20, 2021, 12:20:45 AM
post Re: Some questions about DRSSTC's, and guidance to build one.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
MRMILSTAR
April 19, 2021, 09:59:08 PM
post Re: Help for people buying the "12-48 Volt 1800/2500 Watt ZVS induction Heater"
[Electronic Circuits]
petespaco
April 19, 2021, 09:35:16 PM
post Re: Some questions about DRSSTC's, and guidance to build one.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
AstRii
April 19, 2021, 08:48:07 PM
post Re: gdt high frequency ring
[Solid State Tesla Coils (SSTC)]
balazs
April 19, 2021, 05:03:29 PM
post Intensifying screen
[X-ray]
Merces
April 19, 2021, 04:45:03 PM
post Some questions about DRSSTC's, and guidance to build one.
[Dual Resonant Solid State Tesla coils (DRSSTC)]
mrsebe
April 19, 2021, 04:36:43 PM
post Whoohoooooo
[Dual Resonant Solid State Tesla coils (DRSSTC)]
GrantV
April 19, 2021, 12:29:03 PM
post Please, Share SSTC schematics with me
[Solid State Tesla Coils (SSTC)]
hashtala
April 19, 2021, 10:02:46 AM
post What driver to use for first DRSSTC build
[Dual Resonant Solid State Tesla coils (DRSSTC)]
thedoc298
April 19, 2021, 06:04:03 AM
post Re: Mitsubishi CM300DY-24H IGBT
[Beginners]
thedoc298
April 19, 2021, 02:48:40 AM
post Re: Mitsubishi CM300DY-24H IGBT
[Beginners]
Mads Barnkob
April 18, 2021, 08:04:18 PM
post Mitsubishi CM300DY-24H IGBT
[Beginners]
thedoc298
April 18, 2021, 07:10:24 PM
post Re: gdt high frequency ring
[Solid State Tesla Coils (SSTC)]
balazs
April 18, 2021, 01:11:28 PM
post Re: Drsstc Driver Board for Tesla Coil Driver Optic Fiber Splice
[Dual Resonant Solid State Tesla coils (DRSSTC)]
iw1esu
April 18, 2021, 12:26:48 PM
post Re: Mains synced sstc questions
[Solid State Tesla Coils (SSTC)]
Magneticitist
April 18, 2021, 02:36:34 AM

Sitemap 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 
SimplePortal 2.3.6 © 2008-2014, SimplePortal