Cute CO2 Gauge Tells You When To Crack A Window

March 19, 2024 by Kristina Panos 25 Comments

[Cyrill] has a good home automation scheme going: there are a number of physical switches set around the place that control the essential functions. The only problem is that in the winter time, this results in a great deal of phone checking as [Cyrill] tries to monitor the CO₂ level. Tired of all this screen time, [Cyrill] set about to create an incredibly cute (and useful) Co₂ monitor that plainly shows the current level and how bad it is, relatively speaking.

A large servo and an ESP32-S2 make up the guts of an analog CO2 sensor.

Behind that adorable face is a DS3225 servo being driven by a Wemos S2 mini, both of which [Cyrill] happened to have handy. Although the 25 Kg servo may be complete overkill for the situation, [Cyrill] reports that it is quieter than your average AliExpress alternatives, which makes it well worth it in our book. Then it was on to Inkscape to make the gauge itself. [Cyrill] says they’re an Inkscape noob, but that face could have fooled us.

Finally, it was time to integrate it into Home Assistant to get readings from the CO₂ sensors. This was easier said than done, but [Cyrill] does a nice job of explaining how to get the ESP32-S2 up and working.

If you’re out there monitoring CO levels in your home, beware of fake sensors that cropped up during the height of the pandemic and are likely still at large.

Retro Unit Converter Is A Neat Little Gadget

March 15, 2024 by Lewin Day 10 Comments

These days, unit conversions aren’t something we have to worry about so much. If you’re sitting at a computer, you can usually just tap away in your browser to get a quick conversion done, or you can ask your smartphone for an answer. [HackMakeMod] wanted a bespoke device for this, though, and built a tiny little retro-styled unit converter.

It’s a straightforward build that uses a handful of familiar components. An ESP8266 D1 Mini development board is the heart of the operation, running off a small battery harvested from a disposable vape pen. It runs a 0.96 inch OLED display which has a menu system for selecting from a whole bunch of different unit conversions. Navigating the menu is done via a rotary encoder with an integrated push button. Everything’s wrapped up in a neat 3D printed enclosure that was given a nice worn, weathered finish after printing.

[HackMadeMod] also clearly thought about usability, too. Turning the encoder dial faster ramps up the numbers exponentially so you’re not stuck jogging for ages when you need to enter a bigger figure.

It’s not something a lot of us would have a use case for, given that smartphones are always there and probably faster to use. However, it is a tidy little gadget, and a well-presented one at that. Video after the break.

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Celebrating Pi Day With A Ghostly Calculator

March 14, 2024 by Tom Nardi No comments

For the last few years, [Cristiano Monteiro] has marked March 14th by building a device to calculate Pi. This year, he’s combined an RP2040 development board and a beam-splitting prism to create an otherworldly numerical display inspired by the classic Pepper’s Ghost illusion.

The build is straightforward thanks to the Cookie board from Melopero Electronics, which pairs the RP2040 with a 5×5 matrix of addressable RGB LEDs. Since [Cristiano] only needed 4×5 LED “pixels” to display the digits 0 through 9, this left him with an unused vertical column on the right side of the array. Looking to add a visually interesting progress indicator for when the RP2040 is really wracking its silicon brain for the next digit of Pi, he used it to show a red Larson scanner in honor of Battlestar Galactica.

With the MicroPython code written to calculate Pi and display each digit on the array, all it took to complete the illusion was the addition of a glass prism, held directly over the LED array thanks to a 3D-printed mounting plate. When the observer looks through the prism, they’ll see the reflection of the display seemingly floating in mid-air, superimposed over whatever’s behind the glass. It’s a bit like how the Heads Up Display (HUD) works on a fighter jet (or sufficiently fancy car).

Compared to his 2023 entry, which used common seven-segment LED displays to show off its fresh-baked digits of Pi, we think this new build definitely pulls ahead in terms of visual flair. However, if we had to pick just one of [Cristiano]’s devices to grace our desk, it would still have to be his portable GPS time server.

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Goldilocks Beverage Coaster Tells You When It’s Just Right

March 13, 2024 by Kristina Panos 16 Comments

If you ask us, morning is the only excuse we need for a hot caffeinated beverage — weather be damned. Wherever [gokux] is, they may be experiencing actual winter this year, given that they are out there getting cozy with a hot cup of what-have-you. But how do they know it’s at the right temperature for drinking? Enter the temperature-monitoring smart coaster.

At the heart of this build is a GY-906 infrared temperature sensor, which senses the warmth (or lack thereof) and displays the degrees on a small OLED screen thanks to a Seeed Xiao SAMD21. To make things simple, there is also an ideogram that corresponds to the current temperature — snowflake for too cold, danger sign for too hot, and thumbs up for that just-right range. Although this coaster is mostly 3D-printed, the mug sits on a slotted piece of aluminium that is removable for easy cleaning. This would be a good-looking and useful addition to any desk.

This is isn’t the first temperature-indicating beverage coaster we’ve seen. The most recent one ultimately used a probe, which is likely about as accurate (and messy) as you can get with these things.

2024 Home Sweet Home Automation: Plantpal Is A Friend To You Both

March 8, 2024 by Kristina Panos 7 Comments

One easy way to get started on the home automation front is with something that makes a house a home in the first place — lush, green plants. As nice as it is to have them around, it can be difficult to care (or remember to care) for them all the time.

Plantpal makes easy work of that, with an e-paper display that makes it plain as day how your plant is feeling. As you might expect, it features a soil moisture sensor, but what might be unexpected is that it’s capacitive instead of the usual resistive type. This way, no traces are exposed to the elements of plant life. It also has a BME688 sensor to monitor air quality and CO₂, so your plant has the chance to thrive.

Around back you’ll find an ESP32-C6, an AEM10941 for solar energy harvesting, and another set of solar panels. Be sure to check out the project’s GitHub if you want to learn more about this adorable and useful device.

Beverage Coaster Indicates Ideal Drinking Temperature

March 8, 2024 by Kristina Panos 9 Comments

When temperatures plummet, there’s nothing like a hot beverage to keep you warmed up inside. [Palingenesis] aka [Tim] sure does fancy a nice cuppa, but only within a certain temperature range is it ideal to drink. In an attempt to signal when the time is just right, he created various iterations of a hot beverage coaster.

To be clear, this is a plywood sandwich that does not keep the beverage warm, though that would be an interesting addition to the project. Rather, it indicates when the beverage’s temperature is just right using LEDs. When it’s too hot, the red LEDs are lit. The green LEDs flash while it’s just right, and once [Tim]’s tea has gone cold, the blue LEDs take center stage.

The brains of the operation is an STM8S103F module, aka the Blue Pill, which is paired with a DS18B20 temperature sensor. [Tim]’s original coaster has one in a TO-92 package embedded in the top layer, but ultimately he went with the probe version as it reads a truer temperature by virtue of being directly in the liquid. Be sure to check out the video after the break which covers planning the original version.

If you do want to keep you drink warm, here’s an ESP8266-based solution. If you’re more into looks, check out this blinkencoaster.

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A graph from the article, showing dead zones and error bars for the ESP32 ADC

RP2040, ESP32, And An Atmega Have An ADC-Off

March 7, 2024 by Arya Voronova 31 Comments

[Simon Monk] got frustrated with bad ADC performance when tinkering with an ESP32 board, and decided to put three of the nowadays-iconic boards to the test – a classic ESP32 devboard, a Pi Pico with an RP2040, and an Arduino Uno R3 with an ATmega328P. To do that, he took a bench PSU, added a filter circuit to it, went through the entire ADC range for each board, took a large number of samples at different points and plotted the results. The plots show us both linearity and precision, as well as ADC dead zones, and the results are quite surprising.

The ESP32 doesn’t only have the most limited ADC with maximum 1V input, it also produces the worst results out of all three, with large error bars and sizeable dead zones at both ends. The Pi Pico, despite being colloquially known for its subpar ADC, produces better results than the ESP32. However, both of them are dwarfed by the ATMega328P’s performance. If you need a dedicated ADC, it might just be a good idea to put an ATMega328P on your board.

The example code is provided, and we are wondering whether there are methodology errors. For instance, the ATMega328P code is written in Arduino-supplied C++, but ESP32 and RP2040 in particular used MicroPython, which does more than just running the code, and MicroPython for ESP32 in particular creates a WiFi access point – something known to induce noise into ADC readings. Nevertheless, this is a fun comparison, and we like when hackers do microcontroller standoffs like that – for instance, check out this review from 2017 which pits a dozen microcontrollers of the time against each other!