Month: October 2011

Do You Know WHY You’re Supposed To Use Decoupling Capacitors?

October 25, 2011 by 57 Comments

[Bertho] really enjoyed pawing through the pile of projects submitted to the 7400 logic contest. But one thing kept hitting him with the vast majority of the entries: decoupling capacitors were missing from the circuits. If you’ve worked with microcontrollers or digital logic chips you probably know that you’re supposed to add a small capacitor in between the voltage and ground pins for decoupling purposes. But do you know why? [Bertho] put together a great post that looks that the benefits of using decoupling capacitors in your circuits.

He set up a circuit using a 74HC04 inverter and put it to the test. The image above shows current measurments with the inverter under load. Images on the right show a decoupled circuit and the ones on the left shows a circuit without that capacitor. You can see that the decoupled circuit has much smoother signals when driven high. But it’s not just the smoothness that counts here. [Bertho] goes on to discuss the problem of slow rise-time caused by a dip in current flowing into a chip’s VCC pin. It can take a long time to get above the threshold where a chip would recognize a digital 1. Throwing a capacitor in there adds a little reservoir of current, just waiting to fill in when the power rail dips. This feeds the chip in times of need, keeping those logic transitions nice and snappy.

Singing House Lights Up Halloween Again This Year

October 25, 2011 by 19 Comments

[KJ92508] is flooding the neighborhood with light again this year. Everyone knows of that one house in town that really goes all out, but few put on a show anything like this one. The four Jack-o’-lantern faces lead the way with the opening sequence from A Nightmare Before Christmas. Each has at least four different mouth poses, and two eye orientations which are surprisingly well synchronized with the audio. The image above shows mostly orange lighting, but the home is outfitted with addressable RGB LEDs for a full color performance. In fact, it has seen an upgrade this year, increasing the channels by eight-fold to 1144! Don’t miss the performance which we’ve embedded after the break.

We had considered not featuring this, since we looked in on the same home last year. But the number of tips that rolled in made us think that a lot of you missed it, or are just delighted by the multitude of blinky lights. Either way, it’s worth the four minutes out of your day– it will either put a smile on your face, or make you glad not to live across the street from this guy.

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Recovering A Corrupted EEE PC BIOS

October 25, 2011 by 23 Comments

recovering_eeepc_bios

[Jeremy] had an ASUS EEE PC 1000HE netbook on his hands which had succumbed to a corrupted BIOS. In most situations, people replace a motherboard when the BIOS is damaged beyond repair, but considering the price of motherboards, especially those built for portable devices, he simply refused to go that route.

Instead, he took it apart and did a little investigation to find out what SPI flash chip ASUS used in the netbook. With that information in hand, he put together an SPI flash programmer using a breadboard and a DLP-USB1232H USB to UART module. He couldn’t program the flash chip in-circuit, so he had to desolder it and deadbugged it onto his programmer. Using a few Linux-based flashing tools, he was able to reprogram the chip with a functioning BIOS in short order, saving him from a costly motherboard replacement.

While some motherboard manufacturers have built in secondary BIOS chips to prevent the need for this sort of recovery, it’s nice to know that the process is relatively straightforward, provided you have some basic soldering and Linux skills.

This also isn’t the first time we’ve seen someone recover an EEE PC from the brink – if you’re looking for an Arduino-based alternative, be sure to check this out.

Wicked Use Of HTML5 To Display Sensor Data

October 25, 2011 by 33 Comments

This project shows you one possible way to use HTML5 to fully integrate sensor data from a microcontroller into our technological lives. Now, when we saw this tip come through our inbox we thought it would be an interesting example to learn from but we weren’t ready for how truly cool the setup is. Take a look at the video after the break and you’ll see that scanning the QR code on the project box will immediately start a 10ms resolution live stream of the accelerometer data. Furthermore, the browser page that the phone loads allows you to send what you’re currently viewing to the main frame of a browser running on a different computer with the touch of a button. In this way you can build a dashboard of streaming sensor data. Talk about the future of home automation. Imagine a QR code on your thermostat that allows you gain access to your home’s heating, air conditioning, humidifier, and water heater performance and controls just by snapping a pic? The sky’s the limit on this one so let us know what you’d use it for by leaving a comment.

In this case an mbed microcontroller is handling the data acquisition and pushing that to a server via a WiFly module using the WebSockets library. This data is pushed in the form of a JSON packet which is distributed by the server as a data stream. Clients can access it via a browser through a page that makes use of JavaScript.

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Millivolt Meter Nixie Clock

October 25, 2011 by 9 Comments

Surprisingly, up until a year ago, [Jimmy] hadn’t seen a Nixie tube. Awful we know, but he has come around to the beauty of glowing numbers in a tube. He recently found an old millivolt meter in a junk pile that used Nixie tubes. The wondrous orange glow beckoned him, so [Jimmy] decided to build a clock.

Just about all of the Nixie clocks we’ve seen (including non-clock builds) rely on building a controller for the Nixie tubes. The controllers range from Nixie Arduino shields to the good ‘ol 74141 IC. [Jimmy] realized he didn’t need to bother with controlling the tubes in an already functional millivolt meter – he only needed to send the right voltage.

For his clock build, [Jimmy] used an Arduino to output a voltage through a bunch of resistor dividers. For example, if the time is 12:30, the output voltage will be 12.30mV. Using this technique, the values for the needed resistors don’t exist, so a little bit of PWM means the Arduino keeps fairly good time.

There’s one added bonus of [Jimmy]’s clock – because the voltage varies around 0.01mV, the finished project acts like a digital version of Lord Vetinari’s clock. It may not be perfect, but at least a nice piece of equipment was saved from the trash.

Halloween Hacks: Death Throws A Party

October 25, 2011 by 3 Comments

If you him the Grim Reaper, Azrail, Magere Hein, or simply, ‘Death,’ he sure throws a good party. [Victor] has an anatomical model of a skeleton at his job named [Hein], and for his birthday party, his coworkers decided to throw [Hein] a party.

[Victor]’s first skeleton-based build was last summer. The twinkle of the summer sun in [Hein]’s eye socket made for a great occasion to dress the skeleton up in some summer garb. [Hein] was dressed in a fashionable Hawaiian shirt and put in a window along a corridor. Of course, a skeleton is no good if there’s no element of surprise, so [Hein] held disposable camera that flashed every time someone walked by.

[Hein]’s birthday spectacular required something a bit more shocking. A blowout whistle was added to [Hein]’s mandible. With a PIR sensor and a TI Launchpad, [Hein] was commanded to blow the whistle every time someone walked by.

[Victor]’s builds may not have the shock value – or even be as scary as Halloween necessitates – but he’s got a few good ideas for what could become a great yard display. Check out the video after the break to see [Hein] greeting [Victor]’s coworkers.

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