Open Activity Tracker Webcast

August 28, 2013 by Eric Evenchick 2 Comments

The Upverter team loves their FitBit activity tracking devices, but wanted access to raw data. They decided to build their own Open Activity Tracker that would pump data onto an SD card or to a Bluetooth device for processing.

The device uses MPU-9150 motion tracking IC to gather information on movement. This chip combines an accelerometer, gyro, and compass. It also does on-board processing, providing useful data to your host processor over I2C. The only bad news is that it’s a LGA package, which aren’t fun to solder by hand.

The design also has a SD card, Bluetooth module, pressure sensor, and e-ink display. These are all connected to a low power ARM microcontroller.

The team has been webcasting their design sessions, and tonight [Eric Evenchick] (that’s me) will be joining them as they try to cram all of these components onto a PCB. You can watch the live webcast starting at 8:30pm Eastern.

You can watch the previous design sessions after the break.

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Building A ‘high-end’ USB Audio DAC

August 27, 2013 by Mathieu Stephan 63 Comments

As [Jan-Erik] had already built a simple USB connected Digital-to-Analog Converter (DAC), he decided to make the high-end version of it.

The prototype you see in the picture above is based on:

the PCM2707C from Texas Instruments which takes care of the USB communication and outputs I2S audio data
the PCM1794A, a 132dB SNR 24-bit 192kHz DAC which receives I2S protocol
the OPA4134, a high performance audio operational amplifier

The on-board +3.3V and -5V voltages are generated by inductor-less power supplies. As [Jan-Erik] mentions in his write-up, the ‘high-end’ was put between single quotes because the PCB is single sided and uses through hole passive components. The board was designed using Kicad, etched by himself and put in a machined enclosure. All the production files can be downloaded from his website so you may produce it within a day.

Building An Ethernet Connected RFID Reader

August 26, 2013 by Mathieu Stephan 14 Comments

For the last few years, [Lt_Lemming] was the president of Brisbane’s hackerspace. Until several months ago, access to the local was done using 125KHz RFID tags and an Arduino board with a prototyping shield. As the hackerspace gained members and moved to bigger facilities, [Lt_Lemming] decided to build himself a more compact and advanced platform.

His Simple NetworkAble RFID Controller (SNARC) is a platform which can be connected to an Ethernet network and different RFID readers in order to implement smart access control functionalities. Through hole components were selected so even solder apprentices may assemble it. The PCB was designed using Fritzing, and development can even be done inside the Arduino IDE as ISP and serial headers are available on the board. Finally, an N-channel mosfet controls the door locking mechanism.

The project is open hardware and software, and all the sources can be downloaded from [Lt_Lemming]’s github repo.

Building An Audio Box Out Of Thrown Away Boards

August 24, 2013 by Mathieu Stephan 9 Comments

The last time [Mark] was at the scrap yard, he managed to find the analogue input and output cards of an old Akai DR8 studio hard drive recorder. These cards offered great possibilities (8 ADC inputs, 12 DAC outputs) so he repaired them and made a whole audio system out of them.

The repair only involved changing a couple of low dropout regulators. Afterwards, [Mark] interfaced one of his CPLD development boards so he could produce some sine waves and digitize signals generated from a PC based audio test unit. He then made the frame shown in the picture above and switched to an Altera Cyclone IV FPGA. To complete his system, he designed a small board to attach a VGA screen, and another to use the nRF24L01 wireless module.

Inside the FPGA, [Mark] used a NIOS II soft core processor to orchestrate the complete system and display a nice user interface. He even made another system with an USB host plug to connect MIDI enabled peripherals, allowing him to wirelessly control his creation.

Update: Whistled Platform Upgraded For Simple Word Recognition

August 22, 2013 by Mathieu Stephan 20 Comments

Some people may remember the whistled platform I [limpkin] designed a while back, which recognizes different whistles to control your lighting. Recently, I designed a firmware that transforms the board into a word recognition device, as the 50MHz ARM Cortex M4’s processing capabilities are good enough to do so.

The simple algorithm works by correlating successive Fast Fourier Transforms (FFT) of the amplified microphone output with the FFTs of a template word previously stored in memory. Simply connect the Whistled to your power supply, say the word you’d like it to recognize and you’re good to go.

As you will see in the video embedded after the break (sorry for the accent…), I briefly explain basic principles about word/sound recognition and what you can do to improve your algorithm performances. The source files can be downloaded, as well as the code for my whistle detection algorithm which wasn’t available the first time we looked at the project.

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A Fast And Easy-to-use Vision Sensor

August 21, 2013 by Mathieu Stephan 45 Comments

At Hackaday we don’t often feature kickstarter campaigns, but this one is worth noticing in our opinion. It is called Pixy, a small camera board about half the size of a business card that can detect objects that you “train” it to detect.

Training is accomplished by holding the object in front of Pixy’s lens and pressing a button. Pixy then finds objects with similar color signatures using a dedicated dual-core processor that can process images at 50 frames per second. Pixy can report its findings, which include the sizes and locations of all detected objects, through one of several interfaces: UART serial, SPI, I2C, digital or analog I/O.

The platform is open hardware, its firmware is open source and GPL licensed, making the project very interesting. It is based on a 204MHz dual core ARM cortex M4 & M0, uses a 1280×800 image sensor and can stream the processed camera output to your computer. You can get one Pixy in the kickstarter campaign for $59, which is not that expensive for what it is.

Building An Analog Whistle Detection Device

August 20, 2013 by Mathieu Stephan 11 Comments

Hackaday readers may remember a whistle detection device that I [limpkin] designed some time ago. As [Kevin] saw the new Staff roll call, he discovered this project and wanted to make his version of it.

In contrast with the original Whistled where all the signal processing is done in an ARM Cortex m4 microcontroler, [Kevin] uses discrete components, operational amplifiers and an Arduino Uno to detect someone’s whistle. In his video (embedded below), he goes into great lengths to explain how his circuit works along with the theory behind it. In his setup, his microphone’s signal is amplified, passed through a 1KHz-3KHz passive band-pass filter to a non-inverting amplifier with a 1000x gain (!) and finally to a voltage comparator. The Arduino measures the frequency of the signal coming out from the comparator and triggers a relay if the whistle is a ramp-up / ramp-down.

If you want to make the comparison between the two versions of the electronics, here is the link to the original whistled project.

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