Dumb smoke detector to smart smoke detector the cheap way

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:bangbang:
Disclaimer: NEVER EVER tamper with a smoke detector and NEVER EVER rely lifes on tampered devices like this.
Moreover Photosensors decay over time and make the sensor useless after ~10years after production, rendering them useless
:bangbang:

Hi Guys,

my landlord had to replace my old smoke detectors and told me to throw the old ones into e-waste.
In my case it was a UniTec EIM-211 Smoke detector.

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I am pretty sure that most of the consumer detectors are working the same and since many smart smoke detectors are pricy as hell I decided to share my experiences and lessons I made with you, because it took alot of time for me…

This smoke detector has a soldered in 3v battery and needs to be replaced completely etc. Some need 9v, which might make the whole thing a bit more complicated…

But since mine uses 3v, I removed the battery and connected it to 3.3v and GND on my ESP32.

I then removed the annoyingly loud piezo buzzer and measured voltage.
In my case the “buzz” was ~3v. This means that the buzzer pins might get reused as “sensor” for my ESP.

I did some maths and came to the conclusion that wiring an octocoupler with 330ohm on Pin1 might do the trick, simulating a button press on GPIO4 and GND

I wired everything up, created a simple ESPhome sketch

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substitutions:
####
####
  # Buttons
  octocoupler_pin: GPIO04

esphome:
  name: esp32d1mini-smartsmoke
  friendly_name: esp32d1mini-smartsmoke

esp32:
  board: esp32dev
  framework:
    type: arduino

# Enable logging
logger:

# Enable Home Assistant API
api:
  encryption:
    key: "changeme"

ota:
  - platform: esphome
    password: !secret ota_pw

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: esp32d1mini-smartsmoke
    password: !secret fallback_pass

captive_portal:




binary_sensor:
  - platform: gpio
    pin:
      number: ${octocoupler_pin}
      mode: INPUT_PULLUP
      inverted: true
    name: "Press"
    filters:
      - delayed_on: 10ms

This basic proof of concept - sketch works like a charm and “spams” my sensor states.

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Hope this might help someone to make his smoke detector smart :slight_smile:

Oh yeah and obligatory: I am not responsible for damages done with that detector and dont use it as only smoke detector.
This was just a fun-project I was trying to upcycle e-waste

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Hello The-May,

Except the radioactive element in the device has a halflife and after a few years becomes ineffective in detecting properly.

If it is over 8 YO, it is likely completely useless…

Dispose of as per instructions on the label.

4 Likes
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Oh! Good to know haha. The detector is barely 5 years old and detected smoke before it was swapped out.

1 Like
4

As you can read on the device: the fotocell ones are useless after 10 years, yours is good for another 3 years. “Zu erzetzen” applies to the device, not the battery. The reason it explicitly states batteries are not replaceable is because the battery outlasts the device. The fotocell detector degrades.

If I was your insurance company, I would not pay for fire damages on account of the fact that you messed with the smoke detector. Personally I would not bet my family member’s lives on them either.

5

Wise choice on using an optocoupler. I used a 4N25 in one of my projects which seemed to require 40mA to drive the output.

1 Like
6

Thanks for the clarification.
I rather interpreted this as a “we are not liable after that time, so dont blame us” or a “best before” which doesnt automatically spoils food after that time and did not know that the radioactive thingi there literally decays/becomes useless.

Best example: “best before” on water in Germany, which is just a legal thing and less of a useful thing. :slight_smile:

And regarding “if i would be your insurance company”: yup. Thats why I would never solely rely on this appliance primarily :slight_smile:

7

I was using the PC817 ones and they seemed to work fine… I saw them on some docs and just used them without reading much…

8

As for the fotosensor, it really is no longer reliable. When there is fire, you have but seconds. If you value your life more than the price of the device, replace it before the date passes, not after. This is not a case of the food may taste slightly off, in this case people may die.

2 Likes
9

Thanks for making that clear. I am going to clarify this in the beginning of the Post and add a disclaimer etc.
Thank you very much.

10

The way to calculate risk is:

The risk is the chance that it happens multiplied by the damage when it happens.

If the chance that something happens is low but the damage is high (death), then the risk is still high. For food past the date the damage is low, so the risk is less. Even if the chance is the same.

11

The model pictured is a photoelectric sensor. No radioactive substances involved.

1 Like