Show HN: A subtly obvious e-paper room air monitor

Cool project. I've done something similar using defunct crypto Awair AQI sensors tied into Home Assistant. They have an LED panel in the front that can show overall AQI or any of the pollutants they track: https://www.getawair.com/products/element

The sky is the limit as to what you can do with Home Assistant automations.

It's surprising how quickly a room with a closed door and one person can go from ~ambient CO2 levels to 1000ppm+.

There are lots of commercial gadgets like that.

Most of the affordable CO2 meters are relative, not absolute. They set their 400 PPM level based on the lowest value they ever see. That's usually OK, but it's not good enough for places with permanent people occupancy, such as nursing homes. Absolute detectors with NIST calibration are available but around US$500.[1]

[1] https://www.forensicsdetectors.com/products/carbon-dioxide-d...

You should find a friend's garage, shop or hackerspace with a brake, and metal cutting tools.

I have a similar monitor for equipment metrics, and the cardboard design is similar to the stand I made out of metal. I powder coated the metal light beige and it looks professional.

This is cool! How does it compare to e.g. an Aranet4? I got one to detect when there is a high risk of COVID-19 aerosols lingering and generally carry it in my bag. That way I can check the reading using my phone.

> The air gets "stale": humidity often rises above 60 %

Wouldn't it be easier to just turn on the air conditioner?

I was looking for cheap co2 sensors that can be deployed on RPi but I guess they all feel expensive.

I lived in one house that initially had hot water baseboard heat. A hot-air furnace was retrofitted into a closet and got its "fresh air" from a hole in the closet door (i.e. there was no incoming air). During the winter the air would get extremely "stale." Bathroom smells would linger for hours. It was oppressive.

Germans sure love their Lüften

I found that the e-ink display on my Aranet4 is, by itself, so distracting on screen updates that I had to move it out of my field of view. It's a full-screen flash. Before buying it, I thought e-ink was a good choice for these types of devices, but now I wish they had gone with a cheap segmented LCD. I wonder if you could actually use this to your advantage here, since you want it to be distracting, and you are in control of the refresh.

Slightly off-topic

Home Assistant has been running here for several years, and there are quite a few mammals in a relatively small space (humans and dogs). Air quality plays a significant role in well-being. I spent some time tinkering around to find good sensor solutions (I still use esp32 with bme280/dallas and mhz19 for other rooms), and after some back and forth, I purchased an Awair Element. At first glance, it seems quite expensive, but the sensors alone would cost me 1/3 of the price.

We love it. The little LED that indicates air quality, which I didn't even notice at first, is extremely helpful. The sensors are so accurate that I can see when someone has cooked something, when cleaning products have been used, or when we have a dog visiting. A simple API+web server (which I never needed), as the Home Assistant integration works great.

Great device.

> The air gets "stale": humidity often rises above 60 %,

Fun - I have the opposite problem, humidity goes down to almost nothing and we have to use humidifiers to keep it around 40% to avoid horrible nose/throat/skin dryness.

Forced air hvac is probably why.