Turning An Ordinary Pen Into A Covert Radio Receiver

February 8, 2015 by Rick Osgood 28 Comments

[Ben Krasnow’s] latest project will be good for anyone who wants a complicated way to cheat on a test. He’s managed to squeeze a tiny FM radio receiver into a ballpoint pen. He also built his own bone conduction microphone to make covert listening possible. The FM radio receiver is nothing too special. It’s just an off the shelf receiver that is small enough to fit into a fatter pen. The real trick is to figure out a way to listen to the radio in a way that others won’t notice. That’s where the bone conduction microphone comes in.

A normal speaker will vibrate, changing the air pressure around us. When those changes reach our ear drums, we hear sound. A bone conduction mic takes another approach. This type of microphone must be pressed up against a bone in your skull, in this case the teeth. The speaker then vibrates against the jaw and radiates up to the cochlea in the ear. The result is a speaker that is extremely quiet unless it is pressed against your face.

Building the bone conduction mic was pretty simple. [Ben] started with a typical disk-shaped piezoelectric transducer. These devices expand and contract when an alternating current is passed through them at a high enough voltage. He cut the disk into a rectangular shape so that it would fit inside of the clicker on the ballpoint pen. He then encased it in a cylinder of epoxy.

The transducer requires a much higher voltage audio signal than the litter radio normally puts out. To remedy this problem, [Ben] wired up a small impedance matching transformer to increase the voltage. With everything in place, all [Ben] has to do to listen to the radio is chew on the end of his pen. While this technology might help a cheater pass an exam, [Ben] also notes that a less nefarious use of this technology might be to place the speaker inside of the mouthpiece of a CamelBak. This would allow a hiker to listen to music without blocking out the surrounding noise. Continue reading “Turning An Ordinary Pen Into A Covert Radio Receiver” →

Sonar Built From Piezo And Microphone

January 26, 2015 by Mike Szczys 22 Comments

[Jason] has continued to plug along with his sonar build and recently showed up a monostatic active sonar using a piezo element and microphone. Regular readers will remember [Jason’s] experiments from a Fail of the Week post which focused on his water-proofing woes from a much earlier prototype.

We find this offering far more engaging. He has ditched the ultrasonic module seen in those experiments. The new rig drives the piezo element using a 27V source. After each ping is sent out, the microphone input is immediately captured to detect the return of the audible sound. [Jason] mentions that the TI Launchpad he’s using for the project is fast enough for these experiments but he may switch to a Teensy 3.1 in order to double the RAM and thereby increase the sample size he is able to record.

Of course this is intended for underwater ROVs so his next iteration will involve a DIY hydrophone. We can’t wait to see that one as the process of converting this test rig into one that works underwater evades us. If you have some tips on that topic please let us know in the comments.

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Cheap DIY Microscope Sees Individual Atoms

January 13, 2015 by Matt Freund 144 Comments

This is not an artist’s rendering, nor a physics simulation. This device held together with hardware-store MDF and eyebolts and connected to a breadboard, is taking pictures of actual atomic structures using actual measurements. All via an 80¢ piezo buzzer? Madness.

This apparent wizardry is called a scanning tunneling microscope which takes advantage of quantum tunneling. The device brings a needle atomically close to the object to be measured (by hand), applying a small voltage (+-15V), and stopping when it starts to conduct. Depending on the distance between the tip and the target, the voltage varies and does so precisely enough to identify whether an atom is underneath or not, and by how much.

The “pictures” are not photographs like a camera might take from a standard optical microscope, however they are neither guesses nor averages. They are representations of real physical measurements of specific individual atoms as they exist on the infinitesimal area being probed. It “sees” by measuring small voltage changes. Another difference lies in the “scanning.” The probe examines atoms the way one would draw ASCII images – single pixels at a time until an entire atom was drawn. Note that the resolution – as shown in the pictures – is sub-atomic. Sizes of atoms are apparent as are the distances between them. In this they are closer related to the far more expensive Scanning Electron Microscope technology, but are 10-100x zoomier; resolving 0.00000000001m, or 0.00000000039″.

HAD - STM4 — Scan Head – Piezo cut into quadrants

One would presume that dealing with actual atoms requires precision machining vast orders of magnitude beyond the home hobbyist but, no. Any one of us could make this at home or in our hackerspaces, for nearly free. Apparently even sharpening a tip to a single atom is, as [Dan] says “not as hard to achieve as you might think!” You take some tungsten wire and pull on it as you cut so that it shatters diagonally. There are better ways he suggests, but that method is good enough.

The ordinary piezo buzzer that is key to the measurement is chopped into quadrants with an ordinary X-Acto knife by hand. Carefully, because it is fragile, but, nothing more to it than that. There are two better and common methods but they cost hundreds of dollars, not 80 cents. It should be carefully glued since soldering heat will damage it, but, [Dan] soldered his anyway because it was easier. Continue reading “Cheap DIY Microscope Sees Individual Atoms” →

Sound Reactive Drums Of Trailing Light

January 4, 2015 by Sarah Petkus 8 Comments

If you’re going to be the drummer in a band for a Back to the Future themed New Years Eve party, you really need to add something to your gig that captures that kitschy futuristic ambiance as seen by the 80s. Rainbow LEDs will do the trick.

For his drum set’s reactive trailing light display, [Alec Smecher] was inspired by a similar project he’d seen in the past where Neopixels were added to a regular drum kit and activated with several individual microphones. Since the microphones ultimately heard all of the thundering noise from every drum and cymbal at once, there was a lot of bleed over in the response of the LEDs. To remedy this, [Alec] used piezo pickups which listen to discrete surface vibrations rather than sound in order to clean up the effect produced by the lights. Each of the five LED strips lining the stands of his cymbal and inside of his drums were programmed to react with a burst of light equal in brightness to the intensity of the vibration sensed by the piezo.

To insure everything kept together amidst all the constant motion and shaking during performance, [Alec] soldered his connections directly onto his Trinket’s pins as well as the fragile pickup of the piezo. The pickup of the sensors were taped directly against the skin of his drums and along the inside of each cymbal to maximize responsiveness. After ringing in the new year appropriately as the ‘band from the future’, [Alec] reports that his colorful addition worked fantastic the whole night.

Those interested in building their own can find a nice schematic on [Alec’s] blog as well as the code he used on github. Difficulty level taken into account, this is a great first project for a musician who has yet to dabble in electronics… and seeing that it’s a brand new year, there’s no better time to have a go at something new.

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Create A Buzz With The Mini Electric Ukulele

November 5, 2014 by Theodora Fabio 6 Comments

Everyone’s heard of the “World’s Smallest Violin,” but we think it’s time for something more upbeat. [Simone Giertz] of Punch Through Design has created a mini electric ukulele using a LightBlue Bean. The Bean is an Arduino-compatible microcontroller that you can wirelessly program using Bluetooth low energy (BLE).

The ukulele’s frame is made of laser-cut plywood. Four 1M ohm resistors are soldered to individual wire strings. A different set of wire strings in the ukulele’s neck are connected to the same ground as the Bean. In order to play this tiny instrument, a finger must be kept on the “ground” strings while the other “tone” strings are touched by a different finger. [Simone] uses Arduino’s Capacitive Sensing Library to determine which string is being touched and what the tone will be (indicated in Hz). A piezo buzzer provides the sound. There is no need to fret when the battery is depleted from using this at an all-night luau: the frame can be unscrewed with easy access to the battery. [Simone] has uploaded the Bean’s code to GitHub.

There’s no shame going solo, but we’d enjoy a show of dueling mini-ukuleles. A duet with the 3D-printed ukulele is always a possibility. Or, play this little guy while running up and down some piano stairs while the kettle fife blows off some steam. It’ll be a musical way to brighten anyone’s day. Check out the video of the mini ukelele after the break. You can also see more of [Simone’s] work at her website.

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Pumpkin with a motion detector to deter squirrels

Scare Off Squirrels And Tweet About It With The Jack-O’-Lantern Warning System

October 31, 2014 by Theodora Fabio 3 Comments

[Stephpalm] had carved a pumpkin for the first time in two decades. Unfortunately, the neighborhood squirrels were all too pleased with her work and devoured it. Her original goal for the jack-o’-lantern was to have its lights controlled over the internet. These hungry critters inspired another project instead – The Jack-’o’-Lantern Squirrel Early Warning System. There have been hacks that have dealt with pesky squirrels before, such as a trap and an automatic water turret, but they didn’t have the ability to post to social media like this system does.

The system consists of a Spark Core, a passive infrared (PIR) sensor, and a piezo buzzer. When the motion sensor is triggered the buzzer sounds, scaring away any peckish creatures lurking nearby. [Stephpalm] used an NPN transistor and 1k-Ohm resistor to provide enough current to drive the buzzer. All of these components were connected using jumper wires and a breadboard that sits on top of the pumpkin. As a nod to her original idea, [stephpalm] then created “Pumpkin Watch Code” and loaded it into the Core. It posts preset messages to a Twitter account every 45 minutes of inactivity or whenever a pesky squirrel is detected. The messages can be personalized for anyone who wants to make one of these themselves.

We wonder if it would be better to place the breadboard inside the jack-o’-lantern and carve out a couple of holes on top for the PIR sensor’s wires to come out of. That would offer some protection from the elements and prevent it from getting knocked over. We think this project could be adapted for many other uses. After the break, see a video of the system in action!

Continue reading “Scare Off Squirrels And Tweet About It With The Jack-O’-Lantern Warning System” →

Kickstarter Monitor Will Brighten Your Day

October 16, 2014 by Bryan Cockfield 16 Comments

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.