This IR theremin speaks in four voices

It’s the end of the semester for Scott McKenzie (sjm298) and Alex Rablau (ar568) – both of whom successfully participated in Cornell’s ECE4760 class with the creation of an infrared theremin capable of speaking in four voices.

As HackADay’s Kristina Pano reports, the classic theremin design employs each of the player’s hands as the grounded plate of a variable capacitor in an LC circuit.

“For the pitch antenna, this circuit is part of the oscillator,” Pano explained. “For the volume antenna, the hand capacitor detunes another oscillator, changing the attenuation in the amplifier.”

However, McKenzie and Rablau put a twist of sorts on the traditional theremin by using two IR sensors to control volume and pitch, respectively.

 Essentially, the sensors are tasked with computing the location of each hand, outputting a voltage inversely proportional to its distance from the hand. Meanwhile, Atmel’s ATmega1284P converts the signal to an 8-bit binary number for processing.

“McKenzie and Rablau built four voices into it that are accessible through the push-button switch. The different voices are created with wave combinations and modulation effects,” Panos continued. “In addition to Classic Theremin, you can play in pure sine, sawtooth and FM modulation.”

Although the duo say they are pleased with the current version of the theremin, they are looking forward to implementing further improvements.

“Future iterations of the design could bypass the pulse-width-modulation by using an external digital to analog converter for output actuation. This would free up CPU time to leave additional cycles and memory for more complicated sounds. Also, in its current state, our theremin requires an external amplifier and speaker connected through a standard 3.5mm audio jack,” the two concluded.

“In order to make our theremin truly portable, a built-in amplifier and speaker would be necessary. Furthermore, our input from the user comes in the form of a single-axis distance sensor. Movements which the user makes which are orthogonal to this axis are not seen by our theremin, and produce no response. This is the biggest discrepancy between our theremin and the real theremin, which responds to all user movements of all magnitudes.”

Interested in learning more? You can check out McKenzie’s and Rablau’s theremin here and read about designing a pseudo theremin with Atmel and Adafruit here.

Designing an addressable RGB LED coffee table

A Maker by the name of Alexander has just completed building an addressable RGB LED Coffee Table at a local hackerspace (Sector67) in Madison, Wisconsin.

To kick off the project, Alexander purchased two 4′x8′ pieces of 2.8mm bamboo plywood – after learning art of woodworking at Sector67.

“Having never used a laser cutter before either, Alexander was quickly fed up with the crappy laser interface software, so instead, he hand wrote the shapes as SVGs in notepad and then converted them to DXFs,” explained HackADay’s James Hobson.

“That sounds like a rather slow way to do it, but he thinks it ended up being quicker since it’s all straight lines. Two hours of laser time later, and he had a series of slotted strips to create the grid for the LEDs.”

To illuminate the table, Alexander chose big 12mm RGB LEDs ordered from eBay, which arrived in four strands of 50. A 5V 12A PSU provides power, with an Atmel-based Arduino tasked with addressing.

Interested in learning more about the addressable RGB LED coffee table? You can check out the project’s official page and additional images here.

Atmel powers HackADay’s (offline) Password Keeper

The HackADay crew has chosen Atmel’s ATmega 32U4 microcontroller (MCU) to power its offline password keeper. Known as “Mooltipass,” the platform is also equipped with an easily readable screen, a read-protected smart-card (AT88SC102) and flash memory to store encrypted passwords.

“Atmel’s ATmega 32U4 is the same microcontroller [found] in the Arduino Leonardo, allowing us to use the numerous libraries that have been developed for it. In the final schematics, we’ll add an expansion connector so users may connect additional peripherals (we may switch to a FOUR4 layers PCB at this point),” explained HackADay’s Mathieu Stephan. “The microcontroller’s USB lines are protected from ESD by the IP4234CZ6. For encrypted password storage, we found the cheap 1Mbit AT45DB011D FLASH which also has 2/4/16Mbits pin compatible versions. If our beta testers find that 1Mbit is not enough, upgrading the Mooltipass would be easy.”

As noted above, Atmel’s AT88SC102 was chosen to be the secure smart-card, which offers 1024bits read/write protected EEPROM. In terms of the display, Stephan says the team has temporarily opted for the OLED screen shown in the picture above, although the creation of another mooltipass version with an IPS LCD is more than likely.

“These components choices made the voltages electronics fairly simple. The whole solution is powered by the ~5V coming from the USB, and the ~3.3V required by both the flash and the display is provided by the ATmega32U4 internal LDO regulator (~55mA @ 3.0 to 3.6V),” Stephan continued.

“The +12V also needed by the display is generated by a $1 regulated charge pump DC-DC converter. If we had to use a conventional step-up, the component count (and cost) would be much higher. Notice that we put a P-MOSFET in series with the latter as the output voltage when the DC-DC is not working is not 0V but VCC (here +5V). We also used another P-MOSFET to switch the power supply going to the smart card.”

In addition, the HackADay crew selected two resistor networks R6&R7 as voltage dividers to transform 5V signals to 3.3V.

“Fortunately, the ATmega32U4 can receive LVTTL signals, so we don’t need level shifters to get the data coming from the 3.3v-powered flash memory,” he added.

Interested in learning more about the Atmel-powered Mooltipass? You can check out the project’s official dedicated Google Group page here.

An Uno-powered Photocell Piano

A Maker by the name of Asahillis has designed a Photocell Piano powered by an Atmel-based (ATmega328) Arduino Uno. Originally posted to Instructables, the DIY 6-note musical command center was recently featured on the HackADay website.

“When the user runs their hand over the top of the keys (photoresistors) they turn on audio notes, which can be tuned with potentiometers,” Asahillis explained. “This project utilizes [an Atmel-based] Arduino to turn the notes on and off. The tutorial includes a parts list, schematics and the code required to operate this musical device.”

According to HackADay’s Kristina Panos, the hack uses two circuits: one to generate the tones  and a second to mix them. Essentially, Asahillis adapted Forest Mims III’s schematics for the 555 Tone Maker and the 741 Audio Mixer to create the Photocell Piano.

“When the instrument is powered on, the code takes a 5-second reading of the ambient light, and sets a threshold based on its findings,” Panos explained. “Afterward, the first note will sound, indicating the piano is ready to be played. Each note has its own if-else statement that tells it to sound when its corresponding photoresistor reaches a value below the set threshold (when the player casts a shadow).”

Interested in learning more the Arduino-powered Photocell Piano? You can check out the original Instructables post here.

Building a DIY hearing aid with Arduino

A Maker by the name of “Ojoshi” has designed a DIY intelligent hearing aid prototype powered by an Atmel-based Arduino Mega (ATmega1280). The project, originally posted to Instructables, was recently featured on the HackADay website.

So, just how does the DIY hearing aid prototype work?

First, the platform employs an electret to capture audio, subsequently running it through a pre-amplifier to increase the gain 100x. The next stage consists of four filters – neatly dividing the input signal by frequency into four parts, which are passed into four LTC6910 programmable gain amplifiers, allowing the Arduino to control the gain of each channel. The LTC6910 then takes three digital inputs used to set the gain value.

“To determine which gain to use for each frequency band, the Arduino needs to know how much power is in each band,” explained HackADay’s Eric Evenchick. “An envelope detector averages the signal, which can be read by an analog input on the Arduino. Using this information, the hearing aid can boost specific frequencies when it detects conversation.”

As Evenchick notes, this hearing aid won’t quite fit in your ear, although there is quite a lot of interesting signal processing/action happening on the prototype.

Interested in learning more about Ojoshi’s DIY hearing aid prototype? You can check out the project’s official Instructables page here.

Ben Heck’s glue gun has Atmel under the hood

It’s probably safe to say that most Makers have experienced bad glue gun days. You know, the kind of day that start off nicely enough, only to be ruined by incessant dripping all over the workbench and basement floor. Some of us have even muttered “I bet this doesn’t happen to Ben Heck” under our collective breaths.

As it turns out, master modder Ben Heck probably hasn’t suffered from a bad glue gun day since designing an innovative device that HackADay’s Brian Benchoff describes as “more like an extruder from a 3D printer” than your typical dispenser.

“By far, the most difficult part of this project was the glue stick extruder. For this, Ben used a DC motor with a two-stage planetary gear system,” Benchoff explained.

“This drives a homemade hobbed bolt, just like the extruder in 99% of 3D printers. The glue stick is wedged up against the hobbed bolt with a few 3D printed parts and a spring making for a very compact glue stick extruder.”

On the electronics side, Ben included an Atmel-based AVR board, a thermistor attached to the hot end of the glue gun, a solid state relay for the heater and analog controls for speed /temperature settings.

“The finished product is actually pretty nice. It lays down consistent beads of hot glue and thanks to a little bit of motor retraction won’t drip,” Benchoff added.

We couldn’t agree more!

Designing an Atmel-Arduino RFID car starter

A Maker by the name of Pierre recently decided to celebrate the purchase of his first car by designing a DIY RFID electric starter.

According to the HackADay crew, an Atmel-based Arduino Nano (ATmega328) is tasked with controlling two relays which turn the car on and off.

“Instead of adding a button for ‘push to start,’ Pierre opted for a 13.56MHz RFID module,” explained HackADay’s James Hobson. “Now when he passes his RFID badge across the dash, the car turns on — if it’s held there for over a second, the car starts. Another pass and it will turn off.”

Pierre’s ultimate goal is to move the circuit closer to the wheel and use an NFC ring to start the vehicle.

Interested in learning more about starting a car with RFID tech? You may want to check out HackAday’s archived story about a Maker named Jair2K4 who actually implanted an RFID chip into his hand.

Building a speaking ultrasonic distance sensor

A Maker by the name of Klaus recently built a “speaking distance sensor” to help him park his car.

According to the HackADay crew, the platform is built around an Atmel-based Arduino Uno (ATmega328), an HC-SR04 ultrasonic distance sensor and Adafruit’s Wave Shield.

“Originally, this parking/distance sensor used a small TFT to display the distance to an object, but after a few revisions, Klaus redesigned the device to speak the current distance, courtesy of an SD card and a soothing female voice,” explained HackADay’s Brian Benchoff.

“Right now, the voice is set up to speak the distance from an object to the sensor from 10 cm to 1 m in 5cm increments. This isn’t the limit of the sensor, though, and the device can be easily reconfigured to sense a distance up to four meters.”

Currently, the board lacks an on-board amplifier/speaker, although adding a small amplifier (courtesy of Adafruit) should be sufficiently loud to be heard inside the noisiest parking lots and out in the street.

Interested in learning more about building an Atmel-based speaking ultrasonic distance sensor? You can check out the project’s official page here.

Christmas lights with an Atmel-based Arduino

Thanksgiving may be over, but Christmas and twinkling holiday lights are headed our way. And really, what could be more appropriate for Makers than strings of artfully strung Christmas lights controlled by an Atmel-based Arduino?

One such DIY LED array recently came to our attention, courtesy of the folks at HackADay.

Indeed, a Maker by the name of Anx2k created permanently mounted Christmas lights using LEDs left over from another project. More specifically, the RGB pixels are mounted underneath the tiles on the roof, three per tile, two facing up on either side of the tile and one facing out at an angle in the middle.

“All the wires [run] into his attic where he has an electrical box serving as the main control hub. He uses an Arduino Uno (ATmega328) to control them and a 460W computer power supply to provide the juice,” explained HackADay’s James Hobson.

“The LED modules themselves are Adafruit RGB pixel strings. There’s actually three of the LED modules per tile – two shining up to illuminate the tile, and one shining out.”

As you can see in the video above, Anx2k configured a number of slick patterns for the Arduino Uno to run, including color drop, blended Christmas, spectrum chase, Christmas alternate, random stars and rainbow.

DIY thermal imaging with the Arduino Nano

Many of us have undoubtedly coveted thermal imaging cameras at least once, especially after watching a sci-fi movie or two.

As HackADay’s Brian Benchoff notes, thermal imaging cameras can be an invaluable and practical tool if you are trying to figure just where your latest electronics project will explode/implode next, or attempting to locate a near invisible (and annoying) crack in a glass window.

Fortunately, a Maker by the name of Kaptein QK recently came up with an inexpensive and relatively easy method of making your own thermal imaging camera.

“Kaptein based his camera off of a non-contact IR temperature gun. This device is useful for spot checking temperatures, but can’t produce an IR image like it’s $1000 cousins,” explained Benchoff.

“By taking the thermopile out of this temperature gun, adding an op-amp, an A/D converter, and connecting it to an Arduino Nano (ATmega328) with pan and tilt servos, Kaptein was able to slowly scan the thermopile over a scene and generate an image.”

Although Kaptein’s DIY camera works quite well at this stage, the Maker will likely make additional improvements to the platform in the future.

“[For example], getting rid of the servos and moving to mirrors would hopefully speed everything up, [while] replacing the 8-bit grayscale display with colors would give a vastly improved dynamic range,” Benchoff added.

Interested in learning more about building a DIY thermal imaging with an Atmel-based Arduino Nano? You can check out Kaptein’s forum post here for additional details.