A secret lair isn’t much fun if it’s a pain to get into, so Instructables user SPECTREcat decided to automate his hidden doors using an Arduino Uno. This drives four linear actuators via a MultiMoto shield, which both pull and turn the bookshelf in such a way that the books stay in place.

When opening, the doors first pull apart with one set of actuators, then turn with the other two to allow enough space for a person to pass through. Instead of drilling a hole through the maple plywood shelves, SPECTREcat chose to use a reed switch that’s activated on the other side by a magnet taped inside a DVD cover.

Beyond that, there’ s a PIR sensor that automatically closes the doors if motion isn’t detected for two hours. There’s also an emergency ingress/egress feature in the event of a power failure.

Looking for a hidden bookcase of your own? You can find more on the project’s electronics here, and see how the doors were constructed mechanically in this separate write-up.

After making his first drum with a laser cutter, Ryo Kosaka redesigned it as a 3D-printed structure so more people could build it.

If you’d like to practice playing the drums, but would rather not disturb your family, roommate, neighbors, dog, etc., then an electronic version is probably a good idea. Since you’re reading our blog, making one would be even better!

Although details on how it was interfaced software-wise with the Arduino Uno aren’t included in his log, the drum itself looks quite good. It’s 3D-printed out of several individual pieces, which are glued together using thick paper to help hold everything intact. The sectioned design means that you only need a 120mm x 120mm print area to produce this 8-inch drum pad.

Kosaka also goes into how to set up the piezo sensor for drum use in his write-up, which should be quite useful for this design, or even something derived from it. You can check out the project page for more details as well as Thingiverse for the print files. Additionally, Kosaka recommends this Rockband controller to MIDI Instructable or this one featuring a homemade electronic drum kit.

We’ve all seen geodesic domes in one form or another, whether as a modern experiment, as housing from a bygone era, or perhaps as a gigantic structure in Orlando (technically a geodesic sphere). Jon Bumstead apparently wasn’t satisfied with current dome options, and instead created his own, integrating elements from programmable LED tables to make it interactive.

The resulting build is quite spectacular. Each triangular section able to be lit up with an RGB LED, and further information is output to five MIDI signals in order to produce sound. This means that up to five people can play the dome as an instrument simultaneously. If that wasn’t enough, the Arduino Uno-based dome is programmed to play a version of Simon or Pong, and can be set up to display a light show!

I constructed a geodesic dome consisting of 120 triangles with an LED and sensor at each triangle. Each LED can be addressed individually and each sensor is tuned specifically for a single triangle. The dome is programmed with an Arduino to light up and produce a MIDI signal depending on which triangle you place your hand.

Pretty cool, right? Head over to the project’s Instructables page to see more, or if you’d like information on constructing the dome itself, check out Domerama.

If remembering to hit your foot pedal at the right time during shows is a challenge, this device will take care of it for you.

As creator Franco Molina points out, there’s a lot to worry about when playing guitar in front of an audience. Actually playing is one thing, but you have to pay attention to the crowd, move around on stage, make sure you don’t have any wardrobe malfunctions, and… hit a footswitch to change between clean and distorted channels when appropriate.

Molina’s device may not be able to help you with everything on that list, but by listing to a specially encoded ‘click track’ from a computer or MP3 player, it can automatically switch amplifier modes when appropriate. It does this by using an Arduino Uno along with an amp to listen to the track, then switch a relay to simulate a footswitch.

If you’d like to build your own, check out Molina’s Instructables project page!

There are certainly many ways to generate an old-looking portrait with moving eyes, but this method from Sonic Robots is simple and seems quite effective. The basic formula is to buy a Victorian-like frame, get a picture of a loved/hated/random person (preferably tweaked to resemble an antique oil painting), then put a strip of paper with eyes printed on it behind the person’s eye sockets.

This eyeball strip is pulled by a servo via a fishing line, and importantly, a rubber band keeps tension on it from the other side. This allows it to quickly snap back into place, creating an effect where the eyes randomly move then stay in place for a while, hopefully causing someone to question his or her sanity.

Since everything is Arduino Uno-based, this could be expanded to include sensors for eye control, or even lighting effects as desired.

You can find more details on the project on SonicRobots.com and its code on GitHub.

Using an Arduino Uno along with an Adafruit Wave Shield, Brent Chapman added more features to the Little Tikes Cozy Coupe including a push-to-start ignition and a sound system.

Although Chapman notes that the Coupe comes with some onboard entertainment options, he thought “his client” deserved something a bit more high-tech. This meant that he retrofitted the classic toy with several pushbuttons that allow him to select a fun song to play and replaced the key with a giant arcade button. He also 3D-printed a replacement hood for the car to cover the electronics, since the original was modified to fit them inside.

Per the second video on the project’s page, his little client seems to be hesitant at first, but eventually starts happily car-dancing along to Mickey Mouse Clubhouse’s  “Hot Dog Dance” tune that parents will probably be familiar with.

You can see the entire build, including videos and code, here or follow Chapman on Twitter to see what he’s up to next!

The Cozy Coupe gets a much needed upgrade thanks to @arduino and the wave shield from @adafruit – https://t.co/9Y4UE5Z4Vu #ArduinoMonday pic.twitter.com/U1xWwQF9Bx

— Brent Chapman (@brentmore) January 9, 2017

Sure, if you’re going to get a new ride, a model from the twenty-teens would be nice, but for hacking purposes, the simplicity of an older cars makes modification fairly simple. It also makes hot-wiring easy, and as they don’t generally have an alarm system, these vehicles are often targets for theft.

After his friend’s VW Beetle was stolen, Instructables user Ben Schroeder (aka “Pantopush”) decided that he needed to protect his 1966 Bug. So, as any Maker would do, he took matters into his own hands with a GPS-enabled Arduino Uno in a locked glove compartment.

Now, unless the unit is turned off, if it detects that the car is moving, it uses a relay to switch the horn on. Simple, effective (hopefully), and could be expanded to flash the lights or even text the owner with the location of the car.

Need a low-cost anti-theft system of your own? You can find the full writeup on Schroeder’s project page.

You may know that a neodymium magnet is more powerful than something you usually find on a refrigerator, but by how much?

Most people, even those willing to harvest magnets from disk drives, accept that some magnets are stronger than others. This, however, wasn’t quite good enough for Anthony Garofalo, who instead converted a prototype voltmeter he made using an Arduino Uno and a tiny OLED display into something that displays the magnetic, or Gauss level. It also shows whether it’s observing the north or south pole of the magnet, which certainly could be useful in some situations.

Though full documentation isn’t available right now, Garofalo says that he’ll make it available once he repackages everything in a smaller format with an enclosure. If you’d like to see more of his work, including the voltmeter he based this off of, be sure to check out his Instructables page and some other neat stuff on his YouTube channel!

If you had a Teddy Ruxpin in the ’80s and ’90s, you probably remember inserting special tapes and hearing him read stories to you. Whether you loved or hated the little bear, it was hard to forget his weirdly moving mouth and eyes. Today though, with small and cheap development boards readily available, this mechanical system is just begging for a retrofit.

In this project, hacker “Tinkernut” employed an Arduino to sense the intensity of a sound input, and in turn used it to allow Ruxpin to lip sync to any audio source. This could be a song, story, or even output from a virtual assistant.

He chose the latter option, and after installing Alexa on a Raspberry Pi, used the two boards in tandem to control the retro toy. With this setup, he can ask it such questions as “how tall is the empire state building?” and have it answer back with audio and a semi-synced bear mouth.

Have an old Ruxpin lying around? Give new life to it by following Tinkernut’s instructions here.

If you really don’t want someone messing with your valuables, a programmable box may be just what you need!

Locking mechanisms generally work using one method—a key, for example—to keep them secure, or perhaps two in certain circumstances. This box, designed as a final project for an electrical and computer engineering class at Cornell, instead makes the user go through four steps to get to the “treasures” inside.

Once the user has input the correct code, set potentiometers to the correct position, knocked on the box in the correct sequence, and finally scanned his or her fingerprint, a solenoid unlatches the box’s. It seems like a great project for an ECE class. On the other hand, the unit is wooden, so if you did forget the authentication procedure, it wouldn’t be too hard to manufacture a literal back door!

A cool idea nevertheless, and certainly something that could help protect your snacks or other items from a sneaky roommate. You can see more about this lockbox on the Cornell-hosted project page.