Arduino Hacks

3096 Articles

2025 One Hertz Challenge: Estimating Pi With An Arduino Nano R4

August 9, 2025 by 10 Comments

Humanity pretty much has Pi figured out at this point. We’ve calculated it many times over and are confident about what it is down to many, many decimal places. However, if you fancy estimating it with some electronic assistance, you might find this project from [Roni Bandini] interesting.

[Roni] programmed an Arduino Nano R4 to estimate Pi using the Monte Carlo method. For this specific case, it involves drawing a circle inscribed inside a square. Points are then randomly scattered inside the square, and checked to see if they lie inside or outside the circle based on their position and distance of the circle’s outline from the center point of the square. By taking the ratio of the points inside the circle to the total number of points, you get an approximation of the ratio of the square and circle’s areas, which is equal to Pi/4. Thus, multiply the ratio by 4, and you’ve got your approximation of Pi.

[Roni] coded a program to run the Monte Carlo simulation on the Arduino Nano R4, taking advantage of the mathematical benefits of its onboard Floating Point Unit. It generates 100 new samples for the Monte Carlo approximation every second, improving the estimation of pi as it goes. It then displays the result on a 7-segment display, and beeps as it goes. [Roni] readily admits the project is a little too close in appearance to a classic Hollywood bomb.

We’ve seen some other neat Pi-calculating projects before, too.

Continue reading “2025 One Hertz Challenge: Estimating Pi With An Arduino Nano R4” →

Experience Other Planets With The Gravity Simulator

July 27, 2025 by 8 Comments

As Earthlings, most of us don’t spend a lot of extra time thinking about the gravity on our home planet. Instead, we go about our days only occasionally dropping things or tripping over furniture but largely attending to other matters of more consequence. When humans visit other worlds, though, there’s a lot more consideration of the gravity and its effects on how humans live and many different ways of training for going to places like the Moon or Mars. This gravity simulator, for example, lets anyone experience what it would be like to balance an object anywhere with different gravity from Earth’s.

The simulator itself largely consists of a row of about 60 NeoPixels, spread out in a line along a length of lightweight PVC pipe. They’re controlled by an Arduino Nano which has a built-in inertial measurement unit, allowing it to sense the angle the pipe is being held at as well as making determinations about its movement. A set of LEDs on the NeoPixel strip is illuminated, which simulates a ball being balanced on this pipe, and motion one way or the other will allow the ball to travel back and forth along its length. With the Earth gravity setting this is fairly intuitive but when the gravity simulation is turned up for heavier planets or turned down for lighter ones the experience changes dramatically. Most of the video explains the math behind determining the effects of a rolling ball in each of these environments, which is worth taking a look at on its own.

While the device obviously can’t change the mass or the force of gravity by pressing a button, it’s a unique way to experience and feel what a small part of existence on another world might be like. With enough budget available there are certainly other ways of providing training for other amounts of gravity like parabolic flights or buoyancy tanks, although one of the other more affordable ways of doing this for laypeople is this low-gravity acrobatic device.

Continue reading “Experience Other Planets With The Gravity Simulator” →

Transparent PCBs Trigger 90s Nostalgia

July 25, 2025 by 43 Comments

What color do you like your microcontroller boards? Blue? Red? Maybe white or black? Sadly, all of those are about to look old hat. Why? Well, as shared by [JLCPCB], this transparent Arduino looks amazing.

The board house produced this marvel using its transparent flexible printed circuit (FPC) material. Basically, the stuff they use for ribbon cables and flex PCBs, just made slightly differently to be see-through instead of vaguely brown.

The circuit in question is a Flexduino, an Arduino clone specifically designed to work on flexible substrates. It looks particularly good on this transparent material, with the LEDs glowing and the white silkscreen for contrast. If you like what you see, you can order your own circuits using this material directly from JLCPCB’s regular old order form.

Most of all, this project reminds us of the 1990s. Back then, you could get all kinds of games consoles and other electronics with transparent housings. There was the beloved PlayStation Crystal, while Nintendo did something similar with the N64 while adding a whole line of tinted color and charcoal versions too. Somehow seeing a bit of the inside of things is just cool. Even if, in some cases, it’s just to avoid smuggling in prisons.

It took decades before you could get custom PCBs quickly and easily. Now, board houses are competing for the enthusiast (consumer?) market, and competition is spurring development of crazy stuff like transparent and even glow in the dark PCBs. What next? We’re thinking edible, ROHS and WEEE be damned. Drop your thoughts in the comments.

Thanks to [George Graves] for the tip!

Arduino Saves Heat Pump

July 16, 2025 by 28 Comments

For home HVAC systems, heat pumps seem to be the way of the future. When compared to electric heating they can be three to four times more efficient, and they don’t directly burn fossil fuels. They also have a leg up over standard air conditioning systems since they can provide both cooling and heating, and they can even be used on water heating systems. Their versatility seems unmatched, but it does come at a slight cost of complexity as [Janne] learned while trying to bring one back to life.

The heat pump here is a Samsung with some physical damage, as well as missing the indoor half of the system. Once the damage to the unit was repaired and refilled with refrigerant, [Janne] used an Optidrive E3 inverter controlled by an Arduino Mega to get the system functional since the original setup wouldn’t run the compressor without the indoor unit attached. The Arduino manages everything else on the system as well including all of the temperature sensors and fan motor control.

With everything up and running [Janne] connected the system to a swimming pool, which was able to heat the pool in about three hours using 60 kWh of energy. The system is surprisingly efficient especially compared to more traditional means of heating water, and repairing an old or damaged unit rather than buying a new one likely saves a significant amount of money as well. Heat pump projects are getting more common around here as well, and if you have one in your home take a look at this project which adds better climate control capabilities. to a wall mount unit.

The underside of the scanner is shown. Four power supply units are visible on the lower side, and assorted electronics are visible on the top side. In the middle, two linear tracks adapted from a 3D printer run along the length of the scanner, and several motors can be seen mounted between the rails.

A Scanner For Arduino-Powered Book Archiving

June 29, 2025 by 4 Comments

Scanners for loose papers have become so commonplace that almost every printer includes one, but book scanners have remained frustratingly rare for non-librarians and archivists. [Brad Mattson] had some books to scan, but couldn’t find an affordable scanner that met his needs, so he took the obvious hacker solution and built his own.

The scanning process starts when a conveyor belt removes a book from a stack and drops it onto the scanner’s bed. Prods mounted on a rail beneath the bed straighten the book and move it into position for the overhead camera to take a picture of the cover. Next, an arm with a pneumatic gripper opens the cover, and a metal bar comes down to hold it in place.

The page-turning mechanism uses two fans: one fan blows from the side of the book to ruffle the pages and separate them, while the other is mounted on a swiveling arm. This fan blows away from the page, providing a gentle suction that holds the page to the arm as it turns the page over. Finally, a glass plate descends over the book to hold the pages flat, the camera takes a picture, the glass plate retracts, and the scanner moves on to the next page.

It is hard to imagine, but have a look at the video in the post if you really want to see it in action.

Continue reading “A Scanner For Arduino-Powered Book Archiving” →

Projector on left with red arrow pointing towards object, another red arrow points towards a piece of paper and then camera.

Pictures From Paper Reflections And A Single Pixel

June 29, 2025 by 27 Comments

Taking a picture with a single photoresistor is a brain-breaking idea. But go deeper and imagine taking that same picture with the same photoresistor, but without even facing the object. [Jon Bumstead] did exactly that with compressed sensing and a projector. Incredibly, the resulting image is from the perspective of the projector, not the “camera”.

This camera setup is very similar to one we’ve seen before, but far more capable. The only required electronics are a small projector and a single photodiode. The secret sauce in this particular design lies in the pattern projected and the algorithm to parse the data.

Continue reading “Pictures From Paper Reflections And A Single Pixel” →

The Most Satisfying Way To Commit

June 20, 2025 by 8 Comments

Have you ever finished up a bit of code and thought that typing “git push” in a terminal is just not a satisfying finish? So did [penumbriel], so he built a big red button he could smash instead.

This is a very simple hack: an Arduino sits inside a 3D-printed case that holds a big, red button. The case itself is very sturdily made to withstand a good satisfying smack: it has thick walls, brass insets, and rubber feet to protect the de The code for the Arduino is very, very simple: it spoofs a USB HID using the standard keyboard library, and automatically types out “git push” whenever the button is pressed. Or smashed, because you know you’re going to want to slam that thing. So far, so good– very innovative for 2006, right?

The detail that made this project stand out in 2025 was the technique [penumbriel] used for lettering– we’re always looking

With a simple soap-and-water mask, the cured silicone peels right off, leaving a clean label.

for new ways to make a good front panel. In this case, the letters were printed as a valley and filled with silicone adhesive. To protect the top surface of the print, soapy water was used as a mask. The silicone would not adhere to the wet plastic, so all [penumbriel] had to do was peel it off after it had cured, leaving solid white inside. It’s a neat trick, and a great way to use up an old tube of silicone before it goes hard. You could also use it for injection molding, but this is a great use for the dregs.

This might go well next to the programmer’s macro pad we featured a while back, but it really needs to stay as a big red button for maximum satisfaction.