Author Topic: Reverse engineering a big old American smoke detector  (Read 2812 times)

Offline klugesmith

  • High Voltage Engineer
  • ****
  • Posts: 412
  • Karma: +13/-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: 227
  • Karma: +5/-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: 179
  • 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: 412
  • Karma: +13/-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 120VAC Mains Ramped Builds
[Solid State Tesla Coils (SSTC)]
Magneticitist
Today at 03:00:04 AM
post Re: Muon Decay
[Detection, Counting and Measurements]
alan sailer
Today at 02:16:57 AM
post Re: Help on my "first" SSTC (LabCoatz SSTC 2.0)- Popping transistors
[Solid State Tesla Coils (SSTC)]
TiagoBS
January 20, 2022, 06:56:35 PM
post Re: Muon Decay
[Detection, Counting and Measurements]
Da_Stier
January 20, 2022, 05:19:26 PM
post Re: Muon Decay
[Detection, Counting and Measurements]
alan sailer
January 20, 2022, 03:53:54 PM
post Re: Muon Decay
[Detection, Counting and Measurements]
Uspring
January 20, 2022, 01:20:19 PM
post Re: Muon Decay
[Detection, Counting and Measurements]
Da_Stier
January 20, 2022, 10:11:21 AM
post Re: Muon Decay
[Detection, Counting and Measurements]
alan sailer
January 19, 2022, 08:22:49 PM
post Re: Muon Decay
[Detection, Counting and Measurements]
Mads Barnkob
January 19, 2022, 06:49:36 PM
post Re: Etching PCBs with a SLA 3d printer
[Printed Circuit Board]
hardboiled99
January 19, 2022, 07:37:27 AM
post Primary Coil Winding Technique
[Solid State Tesla Coils (SSTC)]
alan sailer
January 18, 2022, 10:34:48 PM
post Re: Muon Decay
[Detection, Counting and Measurements]
alan sailer
January 18, 2022, 08:46:53 PM
post Re: Muon Decay
[Detection, Counting and Measurements]
Mads Barnkob
January 18, 2022, 08:08:53 PM
post Re: GDT Testing
[Solid State Tesla Coils (SSTC)]
ZakW
January 18, 2022, 07:15:22 PM
post Muon Decay
[Detection, Counting and Measurements]
alan sailer
January 18, 2022, 06:49:48 PM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
304er
January 18, 2022, 08:47:53 AM
post Re: QO-100 / EShail 2 Uplink amplifier development adventures
[Radio Frequency]
Da_Stier
January 17, 2022, 09:13:32 PM
post Re: QO-100 / EShail 2 Uplink amplifier development adventures
[Radio Frequency]
Da_Stier
January 17, 2022, 09:05:56 PM
post Re: Help on my "first" SSTC (LabCoatz SSTC 2.0)- Popping transistors
[Solid State Tesla Coils (SSTC)]
Mads Barnkob
January 17, 2022, 07:45:48 PM
post Re: General Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
January 17, 2022, 07:41:34 PM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
Mads Barnkob
January 17, 2022, 07:38:25 PM
post Re: SSTC with push-pull configuration
[Solid State Tesla Coils (SSTC)]
Mads Barnkob
January 17, 2022, 07:31:03 PM
post Re: GDT Testing
[Solid State Tesla Coils (SSTC)]
Mads Barnkob
January 17, 2022, 07:28:02 PM
post Re: Induction heater Driver for Flyback?
[Voltage Multipliers]
MRMILSTAR
January 16, 2022, 09:00:02 PM
post Induction heater Driver for Flyback?
[Voltage Multipliers]
abstruse1
January 16, 2022, 07:35:26 PM
post Re: SSTC with push-pull configuration
[Solid State Tesla Coils (SSTC)]
Bambinz
January 16, 2022, 12:21:40 PM
post Re: SSTC with push-pull configuration
[Solid State Tesla Coils (SSTC)]
davekni
January 15, 2022, 07:10:03 PM
post Re: SSTC with push-pull configuration
[Solid State Tesla Coils (SSTC)]
Bambinz
January 15, 2022, 06:31:33 PM
post Re: SSTC with push-pull configuration
[Solid State Tesla Coils (SSTC)]
Magneticitist
January 14, 2022, 08:47:43 PM
post Re: SSTC with push-pull configuration
[Solid State Tesla Coils (SSTC)]
davekni
January 14, 2022, 08:39:07 PM
post Re: Unusual Youtube channel activity
[General Chat]
davekni
January 14, 2022, 08:14:17 PM
post Re: Unusual Youtube channel activity
[General Chat]
Mads Barnkob
January 14, 2022, 08:12:13 PM
post Unusual Youtube channel activity
[General Chat]
MRMILSTAR
January 14, 2022, 05:51:52 PM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
304er
January 14, 2022, 08:51:57 AM
post Re: SSTC with push-pull configuration
[Solid State Tesla Coils (SSTC)]
Bambinz
January 13, 2022, 08:20:02 PM
post Re: Help with SSTC feedback circuits with 4046 IC and Schmitt Triggers
[Solid State Tesla Coils (SSTC)]
davekni
January 13, 2022, 05:27:40 AM
post Re: General Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
thedoc298
January 13, 2022, 03:10:32 AM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
304er
January 12, 2022, 06:18:15 PM
post Re: Single mosfet bifiliar gdt
[Solid State Tesla Coils (SSTC)]
alan sailer
January 12, 2022, 05:45:26 PM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
MRMILSTAR
January 12, 2022, 03:29:04 PM
post Re: Help with SSTC feedback circuits with 4046 IC and Schmitt Triggers
[Solid State Tesla Coils (SSTC)]
AFreshLad
January 12, 2022, 01:30:38 PM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
304er
January 12, 2022, 09:09:13 AM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
MRMILSTAR
January 11, 2022, 08:05:27 PM
post Re: Nokia Siemens 3G Flexi 2100MHz 50W Amplifier Teardown
[Radio Frequency]
Mads Barnkob
January 11, 2022, 07:42:12 PM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
Duane B
January 11, 2022, 07:33:15 PM
post Re: 8x MOT transformer, weird power draw
[Transformer (Iron Core)]
AstRii
January 11, 2022, 06:19:49 PM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
304er
January 11, 2022, 05:19:46 PM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
MRMILSTAR
January 11, 2022, 04:31:28 PM
post Re: 8x MOT transformer, weird power draw
[Transformer (Iron Core)]
AstRii
January 11, 2022, 03:21:37 PM
post Re: GDT Testing
[Solid State Tesla Coils (SSTC)]
davekni
January 11, 2022, 06:50:49 AM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
Duane B
January 11, 2022, 06:34:20 AM
post Re: Help on my "first" SSTC (LabCoatz SSTC 2.0)- Popping transistors
[Solid State Tesla Coils (SSTC)]
davekni
January 11, 2022, 06:24:13 AM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
davekni
January 11, 2022, 06:15:08 AM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
MRMILSTAR
January 11, 2022, 05:25:31 AM
post Re: Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
Duane B
January 11, 2022, 12:07:22 AM
post Strange reading for grid feedback coil voltage
[Vacuum Tube Tesla Coils (VTTC)]
MRMILSTAR
January 10, 2022, 10:56:48 PM
post Re: Hi! 811 A tesa coil
[Vacuum Tube Tesla Coils (VTTC)]
Duane B
January 10, 2022, 09:38:53 PM
post Re: Help on my "first" SSTC (LabCoatz SSTC 2.0)- Popping transistors
[Solid State Tesla Coils (SSTC)]
ZakW
January 10, 2022, 07:50:13 PM
post Re: GDT Testing
[Solid State Tesla Coils (SSTC)]
ZakW
January 10, 2022, 07:19:17 PM
post Re: Help on my "first" SSTC (LabCoatz SSTC 2.0)- Popping transistors
[Solid State Tesla Coils (SSTC)]
TiagoBS
January 10, 2022, 03:13:08 PM
post Re: GDT Testing
[Solid State Tesla Coils (SSTC)]
davekni
January 10, 2022, 04:21:46 AM
post Re: Hi! 811 A tesa coil
[Vacuum Tube Tesla Coils (VTTC)]
304er
January 10, 2022, 03:59:09 AM
post Re: 8x MOT transformer, weird power draw
[Transformer (Iron Core)]
davekni
January 10, 2022, 03:54:59 AM
post Re: GDT Testing
[Solid State Tesla Coils (SSTC)]
ZakW
January 09, 2022, 11:45:09 PM
post Re: Hi! 811 A tesa coil
[Vacuum Tube Tesla Coils (VTTC)]
jpvvv123
January 09, 2022, 11:04:25 PM
post 8x MOT transformer, weird power draw
[Transformer (Iron Core)]
AstRii
January 09, 2022, 04:22:11 PM
post Re: Hi! 811 A tesa coil
[Vacuum Tube Tesla Coils (VTTC)]
Duane B
January 09, 2022, 05:52:11 AM
post Re: GDT Testing
[Solid State Tesla Coils (SSTC)]
davekni
January 09, 2022, 05:10:50 AM
post Re: Performance issues regarding phase angle in SSTCs
[Solid State Tesla Coils (SSTC)]
davekni
January 09, 2022, 01:20:40 AM
post GDT Testing
[Solid State Tesla Coils (SSTC)]
ZakW
January 09, 2022, 12:38:28 AM
post Re: General Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
January 08, 2022, 06:36:28 PM
post Performance issues regarding phase angle in SSTCs
[Solid State Tesla Coils (SSTC)]
Max Seiringer
January 08, 2022, 03:21:31 PM
post Re: Hi! 811 A tesa coil
[Vacuum Tube Tesla Coils (VTTC)]
304er
January 08, 2022, 09:05:41 AM
post Re: Hi! 811 A tesa coil
[Vacuum Tube Tesla Coils (VTTC)]
jpvvv123
January 07, 2022, 10:20:10 PM
post Re: Hi! 811 A tesa coil
[Vacuum Tube Tesla Coils (VTTC)]
304er
January 07, 2022, 05:56:28 PM
post Re: First SSTC based on profdc9 PCB Pack
[Solid State Tesla Coils (SSTC)]
davekni
January 07, 2022, 05:15:38 AM
post Re: DRSSTC tuning
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
January 07, 2022, 05:01:21 AM
post Re: How to prevent secondary to secondary to primary arcs?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
January 07, 2022, 04:59:59 AM
post Tophat QCW 1
[Dual Resonant Solid State Tesla coils (DRSSTC)]
dbach
January 07, 2022, 02:27:35 AM
post How to prevent secondary to secondary to primary arcs?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
dbach
January 07, 2022, 02:19:40 AM
post Re: General Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Mads Barnkob
January 06, 2022, 09:33:06 PM
post Re: First SSTC based on profdc9 PCB Pack
[Solid State Tesla Coils (SSTC)]
alan sailer
January 06, 2022, 06:09:39 PM
post Re: DRSSTC tuning
[Dual Resonant Solid State Tesla coils (DRSSTC)]
kubajed
January 06, 2022, 04:48:22 PM
post Re: First SSTC based on profdc9 PCB Pack
[Solid State Tesla Coils (SSTC)]
SK1701
January 06, 2022, 03:05:55 PM
post Re: General Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
AstRii
January 06, 2022, 08:17:09 AM
post General Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
January 06, 2022, 04:42:25 AM
post Re: Hi! 811 A tesa coil
[Vacuum Tube Tesla Coils (VTTC)]
jpvvv123
January 06, 2022, 03:40:43 AM
post Re: First SSTC based on profdc9 PCB Pack
[Solid State Tesla Coils (SSTC)]
alan sailer
January 06, 2022, 12:18:38 AM
post First SSTC based on profdc9 PCB Pack
[Solid State Tesla Coils (SSTC)]
SK1701
January 05, 2022, 08:37:13 PM
post Re: Bus Supply Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Hydron
January 04, 2022, 05:58:10 PM
post Re: Bus Supply Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
AstRii
January 04, 2022, 01:37:02 PM
post Bus Supply Questions
[Dual Resonant Solid State Tesla coils (DRSSTC)]
flyingperson23
January 04, 2022, 04:12:34 AM
post Re: ZVS Driven Teslacoil
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Andrew321
January 04, 2022, 01:14:26 AM
post WTS: small secondary coils
[Sell / Buy / Trade]
dbach
January 03, 2022, 05:38:08 PM
post Re: 60hz synchronous motor on 50hz?
[Spark Gap Tesla Coils (SGTC)]
klugesmith
January 02, 2022, 01:17:37 AM
post Re: 60hz synchronous motor on 50hz?
[Spark Gap Tesla Coils (SGTC)]
paulj
January 01, 2022, 06:53:46 PM
post Re: Single mosfet bifiliar gdt
[Solid State Tesla Coils (SSTC)]
MHV
January 01, 2022, 06:39:05 PM
post DC powered coil. best topology?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Rafft
January 01, 2022, 02:05:43 PM
post Re: Full Bridge SSTC
[Solid State Tesla Coils (SSTC)]
Rafft
January 01, 2022, 11:54:25 AM
post Re: 60hz synchronous motor on 50hz?
[Spark Gap Tesla Coils (SGTC)]
klugesmith
December 31, 2021, 09:50:59 PM

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