Fail Of The Week: Frying FETs With 500mA

January 9, 2014 by Mike Szczys 31 Comments

fotw-mosfet-smoke-at-500ma

When [Simon] fried his 3A rated FET with just 500mA of current he wrote it off to an inability of the SOT23 package to dissipate the heat without a heatsink. For the next iteration of the project he upgraded to a 12A rated part. Luckily he decided to test the circuit one more time before sending his board off for fab. He threw together this constant current load test which led him to discover his failure.

The switching circuit, which was for his home security system project that we’ve seen at least twice, worked just fine up to 500mA. But when he drove it above that threshold the package quickly warmed up. It got so hot that it actually reflowed its solder joints! The problem has to do with oscillation, but even with further testing he couldn’t get the FET to reliably shut off all the way. Take a look at his fail write-up linked at the top and then let us know some possible remedies for the situation.

Fail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.

Retrotechtacular: Tube Amplifiers

January 7, 2014 by Mike Szczys 28 Comments

retrotechtacular-how-tube-amps-work

It’s hard to beat this vintage reel for learning about how vacuum tube amplifiers work. It was put together by the US Army in 1963 (if we’re reading the MCMLXIII in the title slide correctly). If you have a basic understanding of electronics you’ll appreciate at least the first half of the video, but even the most learned of radio enthusiasts will find something of interest as they make their way through the 30-minute presentation.

The instruction begins with a description of how a carbon microphone works, how that is fed to a transformer, and then into the amplifier. The first stage of the tube amp is a voltage amplifier and you’ll get a very thorough demo of the input voltage swing and how that affects the output. We really like it that the reel discusses getting data from the tube manual, but also shows how to measure cut-off and saturation voltage for yourself. From there it’s off to the races with the different tube applications used to make class A, B, and C amplifiers. This quickly moves onto a discussion of the pros and cons of each amplifier type. See for yourself after the jump.

Continue reading “Retrotechtacular: Tube Amplifiers” →

Hackaday: The Gathering

January 6, 2014 by Mike Szczys 83 Comments

1/21/14 – Downtown LA
Come one, come all to a party with [Brian], me, and the Hackaday readers who live in the Los Angeles area. Tickets are free, as is the beer, food, t-shirts, stickers, and other swag which you won’t find out about unless you show up in person.

This is the first official live Hackaday meetup and is open to all ages. During the summer we talked about making Hackaday a virtual hackerspace, and this event is one part of that initiative. We’ll let you in on some stuff we’ve been planning, but in return I expect you to tell us your thoughts on how the Hackaday community can get bigger and better. We’re also using the attendance at this event to judge if we should host more live events (possibly in other cities too). So if you’re in LA get your ticket now and make sure your friends do the same!

UPDATE 3: Get your name on the waiting list… Continue reading “Hackaday: The Gathering” →

Recliner Sofa Given The Power Of The Pi

January 4, 2014 by Mike Szczys 20 Comments

pi-sofa

If you go to buy a sofa these days you’ll not only be greeted with the option of one or more reclining positions, but a fully modern unit comes with motorized reclining. That simply wasn’t convenient enough for [Nicki] and [Kevin] who wanted to control the feature from a smartphone rather than a physical interface (buttons) on the side of the furniture. What resulted is the PiSofa, a Raspberry Pi connected to the furniture’s electronics with the help of a relay board.

This is most certainly a hack, but no doubt one with a lot of finesse. Check out that white PCB. That’s right, it’s a factory spun board to keep things nice and neat. They went with one of our favorite tricks by housing everything inside of a food storage container. After some Ruby coding the Pi now has complete control of the sofa. We’re not overstating this. It literally is the only way to control it because the original buttons no longer work. But that’s okay, turns out not only does it work with their smartphones, but with a [Kevin’s] Pebble watch as well.

We can’t think of any past hacks that specifically targeted the couch. But here’s a hammock that you can drive down the street.

Fail Of The Week: AFSK Build Doomed By Rail Noise

January 2, 2014 by Mike Szczys 19 Comments

fotw-afsk-rail-noise

[Scott] and his buddies were having some fun with their handheld transmitters one day when they decided it was time to build some add-on hardware that could transmit and receive location data. They set their sights on a set of Audio Frequency Shift Keying units that could each encoded and decipher location from the counterpart.

The build got off to an easy start, centering around an Arduino board with a GPS module for capturing precise location data. Next it was time to implement AFSK. On the transmitting side this was done by bit banging the output pins. After a look at the resulting signals on an oscilloscope the team was able to tune the firmware for a pretty tight 1200 and 2200 Hz output. But trouble was brewing on the decoding side of the equation.

The first decoding attempt used the FreqMeasure library written by [Paul Stoffregen]. After no success they moved to a hardware solution in the form of the XR-2211 FSK Demodulator chip. It should have been simple, feed it the signals and read the digital output pins to capture the desired data. This is the point at which you need to click the project link at the top to soak in all of the gory details. Long story short, a noisy power rail was causing sporadic performance of this chip. By the time this issue was discovered interest had waned and the project was ditched as a failure. Was there a quick fix that could have salvaged it such as adding a filtering circuit for that chip? Let us know how you would get this back on track by leaving a comment below.

[Thanks Lewin]

Fubarino Contest Winners

December 31, 2013 by Mike Szczys 28 Comments

fubrino-contest-winners

It is with great pleasure that I announce the winners of the Fubarino Contest (alphabetical order): Brian, Daniel, Dave, Dominic, Eric, Gerben, James, Joel, Joseph, Laurens, Luis, Mats, Mike, Nathanael, Pete, Peter, Sebastian, Taciuc, Vojtěch, and Wes. They rose to the challenge and added our URL as an Easter Egg in their microcontroller project. Their hacks were chosen for their creativity, as well as completeness of presentation. Congratulations! Links to all twenty project features are after the break in reverse order in which they were originally published. To see all the entries hit up the contest tag.

We also want to take a moment to thank Microchip Technology Inc. They not only put up twenty Fubarino SD boards as prizes, they are also covering the cost of shipping to each winner. Many thanks!

We thought it was interesting that the twenty winners live in 11 different countries: Brazil, Canada, Czech Republic, Germany, Malaysia, Romania, South Africa, Spain, The Netherlands, UK, and the USA. Hackaday really is a global community!

If you are one of the winners please leave your acceptance speech in the comments section. This is also a great place to leave feedback — if you didn’t submit an entry we want to know why!

Continue reading “Fubarino Contest Winners” →

Hackaday Links: December 29, 2013

December 29, 2013 by Mike Szczys 6 Comments

There are a ton of cheap RF transceiver boards available. [Martin] recently took a look at several of the most common ones and reports back on what you want to look for when acquiring wireless hardware for your projects.

Ikea picture frame plus old laptop equals a roll-your-own digital picture frame which [Victor] built. It runs Ubuntu and is more powerful and extensible than anything you could purchase outright.

Our friend [HowToLou] sure loves the FlowRider. So much so that he’s trying to figure out how to make them less expensive to operate. He put together an example of how he thinks a standing wave can be created that follows the rider as they move along the surfing area.

[Garrett] released an Arduino library that offers threading, debugging, and error handling. The usertools package can be downloaded from his Github repository.

There’s only one way to gauge your Christmas cheer — hook yourself up to the XMeter built by [Geoff]. He’s the same guy who built a breathalyzer a couple of years back. It flashes images of holiday activities on a television while measuring galvanic response using a couple of DIY probes.

And finally, play around with a virtual x86 system. [Fabian Hemmer] wrote the incredibly full-featured virtual machine in JavaScript. You can get your hands on the code via his GitHub repo. [Thanks Martin]