Sensor Package Aims To Predict Acid Rain

December 1, 2025 by Lewin Day 6 Comments

Acid rain sucks, particularly if you run a fancy university with lots of lovely statues outside. If you’d like to try and predict when it’s going to occur, you might like this project from [Mohammad Nihal].

When rain is particularly acidic, it’s usually because of the combination of sulfur dioxide or nitrogen dioxide and moisture in the atmosphere. This combination ends up making sulfuric acid or nitric acid that then falls to the ground as precipitation. The low-pH rain that results can harm ecosystems, melt statues, and just generally give everyone a hard time.

[Mohammed] decided to try and predict acid rain by building a simple device based on an Arduino Nano. It records SO2 levels with an MQ-136 gas sensor, and NO2 levels with an unspecified MEMS-based sensor. There’s also a DHT11 temperature & humidity sensor in the mix, which is important since moisture content plays a role. The Arduino reads these sensors and uses a simple predictive algorithm to create an “Acid Rain Risk Score” that is displayed on a 16×2 character LCD. It’s all wrapped up in a fun 3D printed enclosure that looks like a cloud.

There are some limitations to the device. Namely, it doesn’t necessarily have a great read on atmospheric SO2 and NO2 levels in the atmosphere, particularly at altitudes where rain is formed, because the sensor sits inside the device indoors. However, the basic concept is there, and improvements could certainly be made with some upgrades and further research.

A small, colorful synth built for a 3-year-old. It has five pots, four sliders, and a tiny screen.

Baby’s First Synth Was Daddy’s First Project

November 22, 2025 by Kristina Panos 7 Comments

We absolutely adore inspired labor-of-love tales such as this one. [Alastair] wanted to build a synth for his daughter’s third birthday in spite of having no prior hardware knowledge. It became the perfect excuse to learn about CAD, microcontrollers, PCB design, and of course, 3D printing.

So, why a synth for a toddler? Aside from plain old ‘why not?’, the story goes that she received a Montessori busy-type board which she seemed to enjoy, and it reminded [Alastair] of the control surface of a synth. He wondered how hard it could be to build something similar that made sound and didn’t require constant button presses.

[Alastair] began his journey by dusting off a 15-year-old Arduino Inventors Kit. The initial goal was to get potentiometer readings and map them to 12 discrete values, and then emit MIDI messages. This was easy enough, and it was time to move to a synth module and an Elegoo Nano.

The full adventure is definitely worth the read. Be sure to check out the pink version in action after the break. You really don’t wanna miss the lil’ panda bear. Trust us.

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Universal Control For The Last Mac You’d Ever Expect

August 1, 2025 by Tyler August 8 Comments

Universal control is a neat feature on Macintosh computers, allowing you to slide your mouse seamlessly from device to device. Of course you need a relatively recent version of MacOS to make it work, right? Not necessarily– thanks to [Bart Jackobs] MacFriends, universal control has come to the Macintosh Classic.

The Arduino is perfect for this purpose, but choosing it ruined a perfectly good pun and we can never forgive that.

Well, not exactly universal control, but similar functionality at any rate. [Bart] can slide his mouse from one side of his retina display over onto the glorious 512 x 342, 1-bit display of his Macintosh Classic, just as if the 68k powered antique was a modern device. As you might expect, the Motorola 68000 in that old Mac is getting a teensy bit of help– though sadly for our love of puns, from an Arduino Nano and not any kind of Teensy.

The Arduino is emulating a mouse and keyboard on the Apple Desktop Bus using code based on the abduino by [akuker]. [Bart]’s custom software on the modern Mac captures the mouse and keyboard inputs to pipe to the Arduino via USB serial. Apple’s Universal control doesn’t require a wired connection between the two machines, of course, but then, it doesn’t work on the Classic. One could imagine redoing this project for Bluetooth communication to have that a same Clarkian feeling of technological magic Apple has always wanted to convey– but nothing was wireless in 1990 except for telegrams and a handful of telephones, so the project is appropriate as-is.

As much as we might resent that micro-controller for ruining a pun, if you want to hook into the ADB– perhaps to use old peripherals with an emulated Macintosh— an Arduino will do the job. So would a Teensy, though, and then we’d have our pun.

Our thanks to [Bart Jakobs] for the tip. Don’t forget to send in your own: the endless maw of the tipsline is always hungry.

2025 One Hertz Challenge: Valvano Clock Makes The Seconds Count

July 14, 2025 by Tyler August 3 Comments

A man named [Jim Valvano] once said “There are 86,400 seconds in a day. It’s up to you to decide what to do with them.” — while we couldn’t tell you who [Jim Valvano] was without a google search*, his math checks out. The quote was sufficiently inspirational to inspire [danjovic] to create a clock count those seconds precisely.

It’s a simple project, both conceptually and electrically. All it does is keep time and count the seconds in the day– a button press switches between counting down, counting up, and HH:MM:SS. In every mode, though, the number displayed will change at one Hertz, which we appreciate as being in the spirit of the challenge. There are only four components: an Arduino Nano, a DS3231 RTC module, a SSD1306 128×64 OLED module, and a momentary pushbutton. At the moment it appears this project is only on breadboard, which is a shame– we think it deserves to have a fancy enclosure and pride of place on the wall. Wouldn’t you be more productive if you could watch those 86,400 seconds ticking away in real time? We think it would be motivating.

Perhaps it will motivate you to create something for our One Hertz Challenge. Plenty of seconds to go until the deadline on August 19th, after all. If you’d rather while away the time reading, you can check out some of [danjovic]’s other projects, like this Cistertian-inspired clock, or this equally-inscruitable timekeeper that uses binary-coded octal.

*Following a google search, he was an American college basketball coach in the mid-20th century.

Adding Automatic Emergency Braking To An RC Car

July 2, 2025 by Lewin Day 1 Comment

Modern RC cars can be pretty darn fast. That’s fun and all, but it also makes it easy to crash them into things. This problem inspired [Narrow Studios] to whip up something to offer a bit of protection.

The concept is simple enough—the RC car just needs some way to detect obstacles and stop before hitting them. The build relies on ultrasonic sensors as rangefinders to spot solid objects in the path of the vehicle. An Arduino Nano is in charge of reading the sensors. When it appears the car is approaching a wall or similar obstacle, it fires off a PWM signal to the car’s motor controller commanding it to brake. The additional hardware is held to the car with a bunch of custom printed brackets.

The setup isn’t perfect; the video notes that if you insist on accelerating quickly when close to a wall, you still have a fair chance of hitting it. That’s largely put down to the refresh time of the sensors and the overall system, which could be improved with further work. Still, if you’re always crashing your RC car into walls or curbs, this kind of thing might appeal to you.

We’ve featured some other great RC projects before, too.

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Blinds Automated With Offline Voice Recognition

February 10, 2025 by Lewin Day 7 Comments

Blinds are great for keeping light out or letting light in on demand, but few of us appreciate having to walk over and wind them open and shut on the regular. [DIY Builder] resented this very task, so set about creating an automated system to do the job for him.

The blinds in question use a ball chain to open and close, which made them relatively easy to interface with mechanically. [DIY Builder] set up a NEMA 17 stepper motor with an appropriate 3D-printed gear to interface with the chain, allowing it to move the blinds accurately. The motor is controlled via an Arduino Nano and an A4988 stepper motor driver.

However, that only covered the mechanical side of things. [DIY Builder] wanted to take the build a step further by making the blinds voice activated. To achieve this, the Arduino Nano was kitted out with a DFRobot Gravity voice recognition module. It’s a super simple way to do voice recognition—it’s an entirely offline solution with no cloud computing or internet connection required. You just set it up to respond to simple commands and it does the rest.

The result is a voice activated blind that works reliably whether your internet is up or not. We’ve seen some other great projects in this space, too. Video after the break.

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A mini Cyclone game consisting of an Arduino, an LED ring, and button, plus a scoreboard on a 16x2 LCD.

2024 Tiny Games Contest: Mini Cyclone Tests Reaction Time

August 29, 2024 by Kristina Panos 3 Comments

Round and round goes the red LED, and if you can push the button when it overlaps the green LED, then you win. Cyclone is almost too simple of a game, and that’s probably part of why it’s so addictive.

Want to make one for your desk? All it takes is an Arduino Nano R3 or comparable microcontroller, an RGB LED ring with 12 LEDs, a 16×2 LCD, a buzzer, and a momentary push button switch.

Interestingly, there aren’t successive levels with increasing speed, but each round begins with a randomized speed value. Of course, this can all be easily changed in the code, which is modified from [Joern Weise]’s original.

This is a tinier version of [mircemk]’s original project, which uses a 60-LED ring and does contain levels. As usual with [mircemk]’s builds, this project is mounted on their trademark 3 mm PVC board and covered with peel-and-stick wallpaper. Be sure to check out the demo and build video after the break.

Don’t forget! You have until Tuesday, September 10th to enter the 2024 Tiny Games Contest, so get crackin’!

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