hacking a smoke detector

adding an ESP-12 with some flipflop magic and MQTT

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I started a youtube video for this but noticed that I need to plan this out more, or I will get 50min videos of me mumbling and rambling... so what's better than starting a project to organise your thoughts? This way I can also watch some editing tips videos on youtube.

This will touch thematics such as self drive piezos, logic gate, IoT stuff, powering things and MOSFETs. A lot to cover in a short video.

Here's the plan:

  • When the alarm / beeper turns on, the ESP will send a message over the internet.

Here are the problems and how I might solve them:

  • beeper signal is not steady
    • work with a flip flop to get around that
    • maybe use PIN7 on the chip (I/O can also be used to activate escape lights, auxiliary alarms, ...)
  • regulator for ESP12 is power hungry (high Quiescent Current)
    • use a MOSFET to turn on power to the regulator

sch - 421.57 kB - 01/02/2017 at 15:52


brd - 86.46 kB - 01/02/2017 at 15:52


  • parts considerations

    davedarko08/19/2017 at 09:23 1 comment 35nA thing that controls pwr converter and shutdown via gpio. only works with up to 5v though, not nine volt battery. so minimal power conversion still would be necessary.

  • vulcan needed, must be good in logic.

    davedarko01/14/2017 at 00:54 0 comments

    01:49 am - no boards ordered.

    When breadboarding around I've noticed that I made a fatal mistake in that I've connected every GND signal, where there should have been two GNDs that will only be connected when the MOSFET is turned on by the 4001 NOR gate RS Flipflop. So at this point the boards can only be used as breakout boards.

    I still have to test the transistor circuit, I think I have it the other way around. I'll test that tomorrow to be fully sure this time. I think I have to pull it low with a resistor and use a PNP instead to reset the flip flop.

  • already revisioning

    davedarko01/02/2017 at 18:26 0 comments

    I thought about using "dual 2 input nor gates" for the flip-flop circuit, because of space and maybe I could add a battery monitoring circuit to it then. But those aren't as cheap as 4001 chips.


    I think I messed up two things:

    1. the signals are not right - the NOR gate outputs should be the other way around
    2. I have no transistor on the ESP to change the state of the flip flop

    I guess I have to wait on the parts and test... meh. Wasted day

  • not only youtube inspirations

    davedarko01/02/2017 at 12:07 0 comments

    Amazon Dash button seems to work in the same way (button activates power supply, device shuts down afterwards)

    This video (and also projects from @Radomir Dopieralski) inspired me to use the Wemos form factor

  • design choice: Wemos shield

    davedarko01/02/2017 at 11:48 4 comments

    I thought a bit about the design and decided to make it compatible to the Wemos D1 board, but also put a minimal "FTDI + ESP12" configuration on there, so the maker can decide what he will build.

    Since GPIO15 is pulled low anyway and I'm able to use it - why not make it the latch off pin.

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