Planet Arduino

Watch any movie about the years of prohibition, and you’ll probably see character gain admittance to a speakeasy by using a secret knock on the door. In the old movies, a little sliding door would open so the doorman could check you out and let you in. With [‘s] electronic lock, the secret knock automatically unlocks the door. You can see a video of how it works, below.

The device uses a piezoelectric speaker to detect the knocking. A speaker is a transducer and like many transducers, it will work — to some extent — in either direction. A servo motor manages the deadbolt. An Arduino runs the whole thing.

The code is relatively simple. It holds an array of projected delays between knocks and compares what it hears to those delays. If you complete the sequence, the door unlocks. We probably would add some extra security if we were locking up the country’s gold supply, but for a light-duty lock, it should be fine.

The circuit is simple, too. There is an analog input tied to a resistor and the sensor. The Arduino is perfectly capable of driving a small servo directly. Add a battery and it is done.

It’s been a while since we’ve seen knock-operated locks around here, but they used to be all the rage. Here is a nice simple one, one that uses logic chips, and of course one built from 555s. If knocking isn’t your style, try replacing the piezo with a button or even a capacitive sensor. You can’t knock it!

When [::vtol::] wants to generate random numbers he doesn’t simply type rand() into his Arduino IDE, no, he builds a piece of art. It all starts with a knob, presumably connected to a potentiometer, which sets a frequency. An Arduino UNO takes the reading and generates a tone for an upward-facing speaker. A tiny ball bounces on that speaker where it occasionally collides with a piezoelectric element. The intervals between collisions become our sufficiently random number.

The generated number travels up the Rube Goldberg-esque machine to an LCD mounted at the top where a word, corresponding to our generated number, is displayed. As long as the button is held, a tone will continue to sound and words will be generated so poetry pours forth.

If this take on beat poetry doesn’t suit you, the construction of the Ball-O-Bol has an aesthetic quality that’s eye-catching, whereas projects like his Tape-Head Robot That Listens to the Floor and 8-Bit Digital Photo Gun showed the electronic guts front and center with their own appeal.

Filed under: Arduino Hacks

In our eyes, there isn’t a much higher calling for Arduinos than using them to make musical instruments. [victorh88] has elevated them to rock star status with his homemade electronic drum kit.

The kit uses an Arduino Mega because of the number of inputs [victorh88] included. It’s not quite Neil Peart-level, but it does have a kick drum, a pair of rack toms, a floor tom, a snare, a crash, a ride, and a hi-hat. With the exception of the hi-hat, all the pieces in the kit use a piezo element to detect the hit and play the appropriate sample based on [Evan Kale]’s code, which was built to turn a Rock Band controller into a MIDI drum kit. The hi-hat uses an LDR embedded in a flip-flop to properly mimic the range of an actual acoustic hi-hat. This is a good idea that we have seen before.

[victorh88] made all the drums and pads out of MDF with four layers of pet screen sandwiched in between. In theory, this kit should be able to take anything he can throw at it, including YYZ. The crash and ride cymbals are MDF with a layer of EVA foam on top. This serves two purposes: it absorbs the shock from the sticks and mutes the sound of wood against wood. After that, it was just a matter of attaching everything to a standard e-drum frame using the existing interfaces. Watch [victorh88] beat a tattoo after the break.

If you hate Arduinos but are still reading for some reason, here’s a kit made with a Pi.

Filed under: Arduino Hacks, musical hacks

If you need a truly random event generator, just wait till your next rainstorm. Whether any given spot on the ground is hit by a drop at a particular time is anyone’s guess, and such randomness is key to this simple rig that estimates the value of pi using raindrop sensors.

You may recall [AlphaPhoenix]’s recent electroshock Settlers of Catan expeditor. The idea with this less shocking build is to estimate the value of pi using the ratio of the area of a square sensor to a circular one. Simple piezo transducers serve as impact sensors that feed an Arduino and count the relative number of raindrops hitting the sensors. In the first video below, we see that as more data accumulates, the Arduino’s estimate of pi eventually converges on the well-known 3.14159 value. The second video has details of the math behind the method, plus a discussion of the real-world problems that cropped up during testing — turns out that waterproofing and grounding were both key to noise-free data from the sensor pads.

In the end, [AlphaPhoenix] isn’t proving anything new, but we like the method here and can see applications for it. What about using such sensors to detect individual popcorn kernels popping to demonstrate the Gaussian distribution? We also can’t help but think of other ways to measure raindrops; how about strain gauges that weigh the rainwater as it accumulates differentially in square and circular containers? Share your ideas in the comments below.

[via r/electronics]

Filed under: Arduino Hacks, misc hacks

Marco Mauro is a physicist currently employed as Scientific Coordinator at Novaetech, the first Spin-off Company of the National Institute for Astrophysics (INAF) in Italy. He shared with us all the info about a project he’s been working on  and based on Arduino Micro.

OpenQCM is a fully open source scientific microbalance capable of weighing mass deposition down to 1 billionth of gram:

The sensing core of the microbalance is a piezoelectric quartz crystal oscillator. The deposition of a very tiny mass on the surface causes the variation in the quartz frequency. openQCM belongs to a new generation of innovative smart sensor which boast high resolution and ultra high mass sensitivity. The open source strategy made the creation of openQCM available at low cost which represents a bit fraction of the cost of similar scientific products.

openQCM was built keeping in mind the emergent principles of the open source hardware movement. The open source hardware gives people the freedom to control their technology through the open exchange of all the project features, 3D design, electronics and software. The open hardware potentiality is even greater when it comes to hardware for scientific applications.

openQCM is exactly something like that, the first open hardware quartz crystal microbalance with applications in a wide range of scientific fields, such as chemical and biological sensing, material science.

openQCM has an Arduino Micro board inside at heart. By hacking the timer counter of the AtMega32U4 Arduino microcontroller, it is possible to measure the quartz crystal frequency variations using the 16 Mhz microprocessor clock. openQCM team has designed an Arduino Micro shield with an embedded quartz crystal oscillator driver circuit and a temperature sensor. The output of the quartz crystal oscillator driver is fed to the Arduino Micro timer counter and the analog value of the temperature sensor is fed to the analog pin of the board. This configuration allow you measure the quartz crystal frequency with a resolution of 1 Hz, which roughly corresponds to a mass resolution of 700 pg over the entire quartz surface in air.

One of the major challenge of an open hardware project is that such devices require funding to prototype and manufacture. That’s why the openQCM team have selected the 3d printing technology to keep high quality and low cost. Using 3d printing to print out the prototypes via the SLS process from OS Formiga P100, P110, P395, and P730, the openQCM team created the device’s parts, which required a precision down to 60 µm.

The open source concept made openQCM publicly available so that anyone (scientists, technology enthusiast, makers, hobbyist …) can study, modify, and develop the hardware based on the original design. openQCM is now working and ready to win the heart of the scientific community and more.

Go and make one yourself!

Keeping up with a kickstarter campaign can be quite a task, especially if your project is real (looking at you, Scribble Pen!) and you’re trying to keep up with product fabrication and all the other logistics involved in bringing a product to market. [macetech] are currently in the middle of a campaign themselves and built a loud, bright alert system to notify them of any new kickstarter backers.

The project uses a LED marquee to display the current number of backers, but every time a new backer contributes to the project, a blindingly bright green arrow traffic signal is illuminated and a piezo speaker plays a celebration tune. All of these devices are controlled by an Arduino Yun which, with its built-in Atheros chipset, easily connects to the network and monitors the kickstarter page for changes.

[macetech] used some interesting hardware to get everything to work together. They used a USB-to-RS232 cable with and FTDI chip to drive the LED marquee and a PowerSwitchTail 2 from Adafruit to drive the power-hungry traffic signal. Everything was put together in a presentable way for their workshop and works great! All of the source code is available on their project page, and you can check out their RGB LED Shades kickstarter campaign too.

Filed under: Arduino Hacks

A simple alarm that will tell you (and everyone else in the room) whenever someone forgets to wash their hands.

Read more on MAKE

[Mastro Gippo] hit Shenzhen back in April and organized a challenge for himself: could he develop an electronic device from idea to product in only 24 hours? The result is the Grillino, a simple clone of the Annoy-a-Tron: a small, concealable device that makes chirping sounds at random intervals. It’s name was derived from a mix of the Italian word for a cricket—”grillo”—and, of course, “Arduino.”

Shenzhen was the perfect setting for his experiment, especially because [Mastro Gippo] was in town for the Hacker Camp we mentioned a few months ago. The build is pretty simple, requiring only a microcontroller, a battery, and a piezo speaker. What follows is a detailed journey of dizzying speed through the production process, from bags stuffed full of components, to 3D-printing a test jig, to searching for a PCB manufacturer that could fulfill his order overnight. Video and more below.

In his haste to arrive at a finished product, [Mastro Gippo] chose a faint-sounding buzzer, which turned out not to be piezo buzzers at all, but small speakers. Though this and other problems prevented him from completing the final version in under 24 hours, we’re impressed with [Mastro Gippo's] enthusiastic sprint through this build and with his stories of the Shenzhen environment. Check out his blog for the rest of the project details and some fond memories of his trip abroad.

Filed under: Arduino Hacks, Microcontrollers

You would think Hackaday would see more projects from public art exhibitions. They really do have everything – the possibility to mount electronics to just about anything in a way that performs interesting but an ultimately useless function. So far, though, [Richard Schwartz's] Flow of Time is on the top of a very short list of public art installations we like.

The idea behind the build is a German phrase that means something similar to ‘time trickles away’. [Richard]‘s project implements this by printing the current time onto the surface of a flowing river in [Richard]‘s native Innsbruck.

The build uses five micro piezo pumps to dispense food coloring from a bridge. Every minute, an Arduino pumps this food coloring in a 5×7 pixel digit to ‘write’ the time onto the surface of a river.

Surprisingly, [Richard]‘s installation doesn’t require much upkeep. The pumps only use about 70ml of food coloring a day, and the entire device – including the Raspi WiFi webcam – is solar powered with a battery backup.

You can see a video of the time printing on a river below.

Filed under: Arduino Hacks

Taking the time to build a reactive target range really adds to the fun of toy weapons. It lets you move beyond just point and shoot to actual games of skill.

The project is anchored by an Arduino board. It connects to a piezo element on the back of each of these sheet metal targets. Detecting when a projectile hits the target works pretty much the exact same way the ever popular Knock-block works. To provide interactive enjoyment each target has an LED which, when lit, indicates that the target is active. From here it’s just a matter of coding to add different challenges. So far [Viktor Criterion] has implemented quick draw, timed, and rapid fire modes. The demo after the break shows off everything, including the slick modular design he came up with to make the system portable.

We’d love to see these targets mounted on motorized tracks. Each round would have the targets moving closer to you at a faster pace to keep you on your toes.

Filed under: Arduino Hacks, weapons hacks