• Nicer enclosure, MP3 playback, amplifier

    Heinz-Bernd Eggenstein • 04/18/2022 at 21:20 • 0 comments

    Finally some progress,

    As an enclosure that is compatible with Neo-Scandinavian interior design (aka IKEA), I gutted a cheap FM radio set that has a nice bamboo front panel, and enough depth to fit one or more Pico's or Raspis. On the video you can see the enclosure opened with the orginal PCB. The breadboard has a Raspberry Pi Pico that does three things:

    1. Using CircuitPython, it plays the sound of a klaxon (stored in an MP3 file)
    2. the generated PWM audio signal is then passed to an audio amplifier
      (see https://learn.adafruit.com/mp3-playback-rp2040 )
    3. a small OLED display is used to show an alert message

    I tried several amplifiers and ended up with a PAM8302A breakout board from Adafruit, as it gave me the loudest sound at acceptable distortion, and matches well the 2W , 8 Ohm speaker that came with the FM radio enclosure. 

    Well, is this overkill? The input is 3.3V PWM, the output from this amplifier is 5V PWM, so probably something much simpler would have worked, but ... I don't care at rhis moment. 

  • But...why???

    Heinz-Bernd Eggenstein • 04/03/2022 at 13:18 • 0 comments

    OK, so with the help of an internet service run by NASA, we can get some advance warning for the next galactic core-collapse supernova, when a star in our own galaxy goes kaboom  and forms a black hole or a neutron star.

    So what? Why would we want to have advance warning for this?

    Will it kill us all and we will want to give our loved ones a last hug?


    No it won't. Well, theoretically it could if it was very very very close indeed, but none of the stars that are sufficiently close are expected to go kaboom anytime soon, so you are pretty safe for now.


    Won't a galactic core-collapse supernova be so obvious an bright that we will know instantly where to look? Why do we need advance warning?  

    A typical core-collapse supernova can outshine its host galaxy and is an intrinsically very bright event indeed. The problem here is that we are sitting in the middle of the galactic disk and the next galactic cc-SN will likely also be in the galactic disk (but at some distance), so we will very likely have no unobstructed  line-of-sight to the event. We will likely have to watch it through some  spiral arms, dust clouds etc in between, which will dim the light of the supernova very efficiently at least in the visual part of the spectrum, where our eyes and most of our cameras are sensitive. If we want to follow the next galactic cc-SN right from the beginning, we will likely need to do some searching to actually spot it as fast as possible. It might not be a bare-eyes event. This is consistent with the fact that humanity missed a few cc-SN in our galaxy in the last couple of hundred years where we only later found the supernova remnants.

    So in the event of a neutrino trigger announcing a galactic core-collapse SN, it will be an all-hands-on-deck situation where we will want every telescope available getting ready to hunt for the optical counterpart. Professionals and amateurs can  contribute to this quest. 

    And that is where tools like the one developed in this project can be useful. We want something that will wake you up at night when an alarm is raised.

  • But....how?

    Heinz-Bernd Eggenstein • 04/02/2022 at 15:59 • 0 comments

    OK, so the task of this project is to produce a nice-looking gadget that will alert the user about a burst of neutrinos reaching Earth, announcing that a star in the Milky Way galaxy had its core collapse under its own weight after running out of fusion fuel. The next step in this cataclysmic event will be that the former core will be converted into a black hole or a neutron star, while the remaining material of the star will "explode" and will form a supernova.

    OK, but can we detect the initial burst of neutrinos with consumer-grade stuff like detectors and electronics? 

    NO. Absolutely NOT. No WAY!

    The only instruments that can detect such burst are scientific neutrino detectors that require huge bodies of water (as ice, sea water or water liquid water in huge underground caverns). Luckily, these scientific events will almost instantly share the detection of such a burst with the world, e.g. thru the SNEWS project (SuperNova Early Warning System). There are several ways to receive alerts from SNEWS, for this project,I plan to use the GCN service provided by NASA).

    So here is the plan:

    Set project requirements:

    • low power : This thing might run for decades without raising an alarm, as galactic core-collapse supernovae are that rare
    • reliable: we don't want to miss that once-per-generation alert so the thingy should indicate when it has a fault
    • nice looking: should not be an eyesore  sitting next to the TV in the living room or near your bed in the bedroom
    • portable: so you can take it with you on travels. For now I'm ok with Ethernet connectivity tho, WiFi can come later


    And the project plan is something like this:

    1. For prototyping: port the Python library PyGCN by Leo Singer et al to CircuitPython, maybe trimming it down to the bare minimum needed
    2. For prototyping: solder a Wiznet5k Ethernet hat to a raspberry Pi Pico µC and make it connect to the public GCN server from NASA
    3. For prototyping: Make some simple circuit to sound a buzzer after a SNEWS (test) alert until the alert is reset by pressing  a key 
    4. Maybe think about an alternative audio output that uses a MP3 etc recording, e.g. from a klaxon
    5. Add an OLED display to the design
    6. Take a nice little FM radio, and try to integrate what we have into it after gutting it. Possible reuse:
      1. the speaker
      2. the volume control knob
      3. existing pushbuttons to reset the alarm or test it
      4. cutouts/windows for the display
      5. the power-supply if possible?