Which way do non-polarized film capacitors go? There is an answer.

orienting-non-polarized-film-caps

If you, like us, thought that capacitor orientation only matters for polarized varieties like electrolytic capacitors you should read through this article. [Bruce Trump] looks at why some film capacitors have a stripe printed on one end and why their orientation can matter.

He has an image rolled into his post showing both axial and dipped capacitors with a black stripe printed on one end of the package. This is an indicator of what is going on inside of the component. The end with the line has a conductive foil layer which acts as a shield. But it seems that this shield will do its job better if you do a better job of designing for the capacitor.

The diagram above shows two op-amp circuits, both using a non-polarized capacitor that will affect the circuit if it receives external interference. [Bruce] discusses various aspects of this phenomenon, mentioning that although these careful layouts can be tested in your designs to prove which has more benefits, simulated applications (using SPICE) will perform exactly the same.

Comprehensive home PCB fabrication tutorial

home-pcb-fabrication

From what we’ve seen we’d say [Jianyi Liu] is really good at etching PCBs at home. Now you can learn from his experience. He just published a mammoth guide to fabricating your own PCBs at home. That link goes to his index page which leads to all eight parts of the guide.

He starts off by mentioning that fab house boards are rather inexpensive these days. This will save you a lot of trouble (like acquiring the equipment and raw materials needed to get up and running) but you can’t beat the turnaround time of doing it yourself.

After discussing the particulars about trace width, copper thickness, and a few design considerations he lays out his board and prints the artwork to a sheet of transparency film. A pre-sensitized board is cut to size before a trip through an exposure rig with the film taped onto it. The image above shows him rinsing the board after applying the developer chemical. From here he uses cupric chloride he mixed himself to etch the board. [Jianyi] recommends populating the components before cutting the panel apart — a task which he accomplishes with a hack saw.

Stellarino brings Wiring-style coding to the Stellaris Launchpad

wiring-for-stellaris-launchpad

[Sultan Qasim] wrote in to tell us about the work he’s been doing on the Stellarino library. It’s goal is to break down the coding barriers present for those looking to move from Arduino to ARM. This is accomplished by facilitating Wiring-stlye code for the Stellaris Launchpad ARM development board.

Right off the bat [Sultan] mentions that the interface is Wiring-like, but is not compatible with it. This means you can’t just plop your existing sketches into a C file and get them to work with the addition of a simple include file. But what it does do is provide access to the functions to which seasoned Arduino users have grown accustomed. You can see some examples above, including analogWrite(), digitalRead(), and a simple delay function.

We had a quick look at the library. It uses StellarisWare components which are stored in the ROM of the chip (these are all preceded by ‘ROM_’). The one thing missing is the UARTstudio library which apparently carries a license incompatible with GPL.

Months of failure lead up to this EL panel dimmer that pulses to the music

el-panel-dimmer

Way back in March [Ch00f] took on a for-hire project to make a suit that lights up to the music. He decided to build something based around a pulsating EL panel. He’s put a lot of time and tried of a few different techniques, but he finally has a working EL panel dimmer.

This is a saga we’ve kept our eye on. The fall seems to have been good to him, after a failure using TRIACS he managed to adjust the brightness of some EL wire by messing with the current going to the driver’s oscillator. Standing on the shoulders of that success he designed the board seen above by getting serious about audio signal processing. There’s a microphone on the board which picks up sound which is then processed into a signal responsible for the brightness of the EL panel.

There’s a demo video after the break, but you’ll want to dig into his article to get all the gritty details.

[Read more...]

Sound reactive Christmas tree makes folks happy

public-square-holiday-tree-is-sound-reactiveThis non-traditional Christmas tree in Victoria, British Columbia is bringing people together this holiday season. It boasts over 800 lights that react to sound. You can see the pulsing and color changing that go along with some Tuba carols in the clip after the break.

The art installation was commissioned by the Downtown Victoria Business Association. A great big cherry tree was adorned with strings of individually addressable RGB LED Christmas lights. They are controlled by a system which calculates changes based on onset, energy and frequency analysis of sound picked up by multiple microphones. The effect is delightful and it’s not just musicians getting in on the fun. Passersby can’t seem to help themselves from yelling, clapping, and singing to make the tree sparkle.

Also included in the project is an interactive stop-motion animation film. It’s projected on the side of a building and invites viewers to send a text message to interact with it. A video of this is also found after the jump.

[Read more...]

Reverse geocache based on STM32 and GPS wristwatch

reverse_geocache

[Renaud Schleck] somehow got lucky enough to find a GPS wristwatch in the trash. It had a broken LCD screen so its wouldn’t be of much use on that next hiking trip, but he knew it still had potential. He used the GPS module and a few other parts to build this reverse geocache box.

Reverse geocache is a container that is locked, opening only in a pre-defined geographic location. We’ve seen plenty of these projects around here, like this one that talks, or this one which was given as a Christmas gift. They’re popular projects both because of the unique method of getting at the prize inside, and because it doesn’t take a whole lot of hardware to build one. Once [Renaud] had the GPS module he simply need a user interface, locking mechanism, and a microcontroller to pull it all together.

The interface uses a screen from an old cellphone and one push button. The latching system is a tiny geared motor salvaged from a Laptop optical drive. These, along with the GPS watch board are all monitored by the STM32 microcontroller which he programmed using OpenOCD and the Bus Pirate.

[via Reddit]

Stellaris Launchpad and booster packs used as frequency analyzer

stellaris-frequency-analyzer-using-booster-packs

[Jordan Wills] got tired of being limited to eight pixels of resolution and having jumper wires littering his work space. He set out to upgrade his Stellaris Launchpad frequency analyzer project using booster packs. You may remember the initial iteration of the project which used an 8×8 LED matrix to map audio spectrum. With this upgrade he’s really putting the power of that ARM chip to use.

His first improvement with this project was to spin his own audio input board. It has a standard headphone jack for input and a few passive components to shift the signals to rest nicely within the ADC measurement range. The shield has two double pin headers and a group of four stand offs to serve as legs. This way it plugs into the female headers on the bottom of the Launchpad and provides a stable base for the assembly.

The second portion of the setup is an LCD booster pack for the hardware. Kentec manufactures this 3.5″ 320×240 LCD (EB-LM4F120-L35) complete with a resistive overlay making it touch sensitive. The increase in resolution, and availability of different colors gave [Jordan] plenty to work on. Since this add-on is designed for the Launchpad and has a driver library already available he was able to focus on adapting the FFT output for display and adding in new features. Don’t miss seeing what he’s accomplished in the clip after the break.

[Read more...]

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