Cheap Open-source Pace Clock Keeps Your Practice On Schedule

May 10, 2011 by Mike Nathan 10 Comments

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Pace clocks are used in a variety of sports, from swimming to track. The systems are typically expensive however, often beyond the reach of smaller organizations and underfunded programs. For their electrical and computer engineering final project, Cornell students [Paul Swirhun and Shao-Yu Liang] set out to build a much cheaper alternative to commercial pace clocks, with a far simpler wireless user interface.

Their clock uses an ATmega32a to handle all of the processing which is paired with a RN-42 Bluetooth module for communicating with Android smartphones. Their seven-segment displays are built using custom PCBs that they designed and fabricated for the project which are controlled by TLC5940NT LED drivers. The Android software allows users to connect to the pace clock remotely, creating any sort of multi-layered swimming or running routines.

When the project was completed, the pair tallied their total hardware cost to be under $250 apiece at low production volumes. Even when taking assembly time into account, their solution is several magnitudes cheaper than similar commercial systems.

Stick around if you are interested in seeing a demo video of their final product in action.

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DIY Sound Localization Sensor

May 10, 2011 by Mike Nathan 32 Comments

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Sound localization is very popular in law enforcement circles due to its accuracy and ability to quickly separate gunshots from other similar noises. These systems don’t come cheap, and after trying to build one himself, [Fileark] knows why.

He thought it would be neat to build a sound localization sensor based on how the human ear determines a sound’s source. Once he got started however, he realized just how hard it was to do localization just right.

He used an LM324N op-amp as a volume comparator, which he says works decently enough though he figures there are ICs out there that can do a better job. [Fileark] reports that the sound detector works well when the source is within about a foot of the sensors, but performance deteriorates at greater distances. He may consider using an ARM Cortex-M3 as his sound processor if he builds a second version, since the Arudino he used just doesn’t have enough power to sample and run calculations within the 10-50 microsecond window he requires.

Keep reading to see a video of his sound localization sensor in action.

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Roll Your Own Capacitors – High Voltage Edition

May 10, 2011 by Mike Szczys 13 Comments

[Grenadier] tipped us off about his method for building your own high-voltage capacitors. He thought the paper and foil capacitor project was a nice introduction to the concepts, but at the same time he knew he could produce a much more powerful device.

For the dielectric he is using acetate film. This is the material from which overhead transparency sheets are made. He stuck with aluminum foil for the two plates. Just roll the foil flat with a rolling-pin, use thin wire to minimize the air that will be trapped between the dielectric layers, and make sure the foil plates are at least 4cm shorter than the acetate film on each end to prevent leakage. After rolling and securing the capacitor with zip ties you’ll be ready for the 3nF worth of fun seen in the video after the break. [Grenadier] mentions that this can be improved further if you were to vacuum impregnate the device with beeswax.

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Jeri Ellsworth’s Shooting Gallery

May 9, 2011 by Caleb Kraft 8 Comments

Back with another interesting vidoe, [Jeri Ellsworth] once again brings us an amusing and educational hack. This time she’s made a “shooting gallery” in the style of the old arcade games that actually used projectiles. In her version however, she’s using LEDs in the targets which are detected by the gun. In an effort to keep the feel the same, she rigged up a pinball bell to ding at the appropriate times and it is quite effective.

As usual, she does a great job of breaking everything down and explaining how it all works. She shows us around her prototype so you can see how it is constructed, if you can make it through the solder gun shootout in the beginning. If she were to continue with this project beyond the functional prototype stage, we’d love to see small video clips being displayed for the targets pepper’s ghost style. Maybe we’re just having fond memories of Time Traveler.

Roll Your Own Capacitors

May 9, 2011 by Mike Nathan 30 Comments

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Rolling your own electronics components can be fun, but can also help in explaining how certain items actually work. [Addie] from The Toymakers recently set off to figure out how capacitors work, by making her own.

She understood the general concept behind capacitors and how they are constructed, but she wanted to see how it was done first-hand. To construct her capacitor, she selected aluminum foil as her conductor, and saran wrap as the dielectric. She admits that her first attempt was a failure, but undaunted, she carried on. Friends suggested that her conductors were a bit too small to hold any reasonable charge, so she tried larger sheets of aluminum foil to no avail.

She kept at it and found success after using several feet of foil to construct her capacitor. She charged it with a handful of AA batteries and was excited to see her multimeter come to life when she touched the leads to the cap.

While you likely wouldn’t use a hand-made capacitor in your next build, it is a fun experiment to do with children interested in learning about electronics.

[via Adafruit blog]

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Digital Picture Frame Reverse Engineering

May 7, 2011 by Mike Nathan 22 Comments

coby_frame_hack

A few months ago [Jason] got his hands on a free Coby DP700WD digital picture frame and thought it would be fun to hack. After realizing that the frame did not run any sort of Linux-based OS he figured his options were pretty limited, but he gave it a shot anyways.

The frame came with a set of built in images, and his goal was to swap them out for pictures of his own. He started by trying to read data from the frame’s serial flash chip, but found that the processor was preventing him from doing so. He de-soldered the chip from the frame, mounted it on a makeshift breakout board, and started reading up on SPI.

He was eventually able to read the device’s flash chip and swapped out the built-in images with his own. After a bit of trial and error, he was able to replace the frame’s boot screen with his own custom image as well.

If you are looking to do something similar, be sure to swing by his site – all of the tools and code he used to hack his frame are available for the taking.

Continue reading to see his modified picture frame in action.

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Mini Light Table Fits Inside A Briefcase

May 5, 2011 by Mike Nathan 38 Comments

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Hackaday forum member [Mike] was looking for project ideas when his girlfriend, an art major, suggested that he build her a light table to help with her various assignments. Having seen a few of these projects pop up from time to time, he figured he was up to the task. He started hunting around at his local thrift stores and finally came across what he was looking for – a hard-sided Samsonite briefcase.

He ripped out the bottom lining of the briefcase and proceeded to paint the inside white in order to properly reflect the lighting he would be adding shortly. A pair of under-cabinet lights were installed, and wired to be easily toggled on the outside of the case. He located some white acrylic to serve as the top of the table, trimming it to fit snugly in the case without any need for fasteners.

His girlfriend loved the table, though we would be interested in seeing a more portable version – it is built into a briefcase after all. We would love to hear your suggestions on how he might make this more portable, so let us know in the comments.