• 8 Posts
  • 269 Comments
Joined 2 years ago
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Cake day: June 13th, 2023

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  • Maybe the best way to think about it is not dark, but the absence of more light.
    On a DMD projector, we use tiny micromirrors for each pixel which flash thousands of times per frame of video.
    The flash/no-flash ratio decides how much light makes it out of the projector. This gives us over a thousand light levels per colour channel, from near dark, to full light.
    When the mirrors are not in position, the light output is very low. (1/1000th of the full output, on a projector with a static 1000:1 contrast ratio)

    The screen is designed to reflect light well, which means in a non-perfect room, it will have a light floor of the reflected ambient light, plus whatever still makes it through the projector (as Cygnus mentioned, room treatment).

    If you do treat a room well enough that the small amount of light that makes it through the projector at all-off is a problem, you can do things like fitting an ND filter to the lens (reducing the full light output, while also reducing the minimum).
    Or you can use the dynamic iris fitted to some projectors (which reduces the amount of light being put out based on the overall scene illumination, similar to the way LCD TVs lower the backlight level to “reach” contrast ratios of 100000:1).


  • The biggest one was probably a combo of having an anemometer, and heat/humidity sensors in each room.

    When it’s cold outside, the top floor of the house (loft conversion) loses more heat. But it loses significantly more heat when it’s cold, and the wind is blowing parallel to the floor joists.

    I realised that because they’re not perfectly sealed (old house), enough air pressure means that the floor void can easily hit external temperatures, meaning the rooms have cold on twice as many sides.

    I will (eventually) get some suitable insulation in them to stop this.








  • For a low tech solution, you could use cold chain labels.
    They indicate when a temperature threshold is breached. So you’d at least know when a vial was spoiled. They’re not cheap, mind, when you only want a few.

    But I know that’s not solving the problem in the way you wanted to!

    If you only need to know when a threshold is exceeded, you could make something simple using (for example) an esp with a PAYG SIM card and a temperature sensor.

    Then set it up to SMS an alert when temperatures go out of bounds. And pick the SMS up in HASS (various ways). That way, you’ll only be spending a few cents each time there is an issue.

    You could also use mobile data if you felt more fancy, and post straight to HASS.









  • I use them, and I love them.

    They’re banned from the internet, and never complain.
    I use both SD cards inside the cameras, and dumps over SFTP.

    The general standard of integration with HASS is very good (IR control, alerts, streams, etc.)
    If you want to access streams over a VPN, make sure that you configure the IP addresses manually in the app, rather than letting it auto-find (took me a while to work this out).

    Doorbell cam: Lovely bit of kit. Button press and person detection hooks in nicely with HASS things.
    I really like being able to answer delivery people (and be silly with visitors). 2-way audio works well in the app, I keep meaning to try integrating it with HASS now the latest version has capability baked in.

    810A: Decent picture quality, the only fly in the ointment is that it uses H265 for full res, and a lot of open source things don’t officially support it.

    510: Good value, and decent quality image. There is a firmware floating around that adds pet detection features too.


  • Hue bulbs now work on standard zigbee.
    I’d have to double check that the newest ones still do, but unless Signify are being complete bell-ends, it should just work.

    I switched mine over after I got fed up with that bloody hub requiring an app to do any serious config, and randomly disconnecting.
    The response time seems better when using HASS too. Bulbs that are not yet paired can be easily added to the network, ones that have been paired need to be deprogrammed first.

    This is how the Hue RGB bulb I have can be controlled in HA:

    It’s fair to say that there really isn’t one standard yet for home automation.
    You’re likely to end up with multiple radios just due to availability of products.
    I started with a zigbee dongle, then got a z-wave one when I started finding products I wanted that only came in z-wave.
    Then I got an SDR dongle to use 433MHz (lots of cheap gear uses 433)

    I personally haven’t touched thread/matter yet.

    The really nice thing about HASS is that if you can get it to talk to HASS…It can be integrated with anything else you integrate with HASS.
    For example, I have some cheap zigbee push buttons.
    One click toggles the hue bulbs for that room on/off. Two clicks toggles a daylight mode.
    Press+Hold toggles a dim yellow mode for night.

    Or for another, I have central water heating.
    The toggle for heating on/off is a simple smart switch.
    This is linked to a virtual thermostat in HASS, which in turn is fed by a simple thermometer that also feeds into HASS.

    You can often make really nice integrations by keeping the hardware as simple as possible, then stitching it together with HASS.
    Rather than buying one thing for all, and hoping it integrates well.