Fail Of The Week: Color Meter For Adjusting LEDs

January 16, 2014 by Mike Szczys 29 Comments

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[John Peterson] answered our call to document your hacks by discussing what he learned while building this color meter. He conceived the project as a way to precisely match the color output of LEDs driven with a PWM signal. The thought was that it could sample an LED’s output, then use that data to calculate values necessary to match the color of other LEDs. This is a good idea when using LEDs of different types, but even diodes from the same production line can show variations in color output.

Of course this project wouldn’t be featured as a Fail of the Week if it worked as he had expected. It turns out the sensor that he used, an Avago ADJD-S371-QR999 on a SparkFun breakout board, takes very quick color readings. This is great for solid objects, but not great for a light source being switched on and off like the PWM LEDs.

We like it that [John] posted a list of lesson learned on the project. The real fail is in trying to use this particular sensor, but we figure there must be some way to get meaningful data through sampling. Check out the page for the retired sensor which also includes a link to the datasheet. Can you think of a firmware hack which would allow this hardware to sample so that the PWM value could be extrapolated through averaging or other calculations? Let us know in the comments.

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.

3D Printering: Making A Thing With SketchUp

January 15, 2014 by Brian Benchoff 22 Comments

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Imagine for a second it’s the mid-1980s and you’re looking in to desktop publishing setups. Those new LaserJets and LaserWriters are pretty cool, but imagine the desktop publishing world if you couldn’t create your own documents. Yes, it seems absurd to have a printing press that won’t create unique documents.

Now flash forward 30 years to the world of desktop manufacturing and rapid prototyping. There are dozens of repositories for 3D printable objects, but making something of your own design is apparently a dark art and arcane knowledge to everyone buying 3D printers for plastic octopodes and bottle openers.

This week, by popular demand, we’re going to be making a ‘thing’ in SketchUp Make. It’s free, easy, and surprisingly versatile despite its limited tool set. Common sense and Google algorithms dictate I link to previous tutorials in this series below:

And now on with the show. You’re gonna want to click the ‘read more’ link.

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Retrotechtacular: The Genesis Of The Transistor

January 14, 2014 by Kristina Panos 36 Comments

Few births are easy. Even fewer result in a Nobel Prize, and hardly any at all are the work of three men. This 1965 film from the AT&T archives is a retrospection on the birth of the transistor nine years after its creators, [Walter Brattain], [John Bardeen], and [William Shockley] received a Nobel Prize in Physics for their discovery and implementation of the transistor effect.

The transistor is the result of the study of semiconductors such as germanium. Prior to the research that led directly to the transistor, it was known that the conductivity of semiconductors increases when their temperature is raised. The converse is true for metals such as tungsten. Semiconductor conductivity also increases when they are exposed to light. Another key to their discovery is that when a metal such as copper is in contact with a semiconductor, conductivity is less in one direction than the other. This particular property was exploited in early radio technology as seen in crystal radios, for copper oxide rectifiers used in telephony, and for microwave radar in WWII.

After WWII, AT&T’s Bell Labs put a lot of time and research into the study of semiconductors, as their properties weren’t fully understood. Researchers focused on the simplest semiconductors, silicon and germanium, and did so in two areas: bulk properties and surface properties. During this time, [Shockley] proposed the field effect, supposing that the electrons near the surface of a semiconductor could be controlled under the influence of an external electric field.

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Hackaday Links: January 12, 2014

January 12, 2014 by Brian Benchoff 7 Comments

[Kyle] teaches photography and after being dismayed at the shuttering of film and darkroom programs at schools the world over decided to create a resource for film photography. There’s a lot of cool stuff on here like mixing up a batch of Rodinal developer with Tylenol, lye, and sodium sulphite, and assessing flea market film cameras. There are more tutorials coming that will include setting up a dark room, developing prints, and playing around with large format cameras.

[hifatpeople] built a binary calculator out of LEGO® bricks or toys. It started off as a series of logic gates built out of LEGO® bricks or toys in the LEGO® Digital Designer. These logic gates were combined into half adders, the half adders combined into full adders, and the full adders combined into a huge plastic calculator. Unfortunately, buying the LEGO® bricks or toys necessary to turn this digital design into a physical model would cost about $1000 using the LEGO® Pick-A-Brick service. Does anyone have a ton of LEGO® Technic® bricks or toys sitting around? We’d love to see this built.

Think you need a PID controller and fancy electronics to do reflow soldering in a toaster oven? Not so, it seems. [Sivan] is just using a meter with a thermocouple, a kitchen timer, and a little bit of patience to reflow solder very easily.

The folks at DreamSourceLabs realized a lot of electronic test equipment – from oscilloscopes and logic analyzers to protocol and RF analyzers were all included a sampling circuit. They designed the DSLogic that puts a sampler and USB plug on one board, with a whole bunch of different tools connected to a pin header. It’s a pretty cool idea for a modular approach to test equipment.

Adafruit just released an iDevice game. It’s a resistor color code game and much more educational than Candy Crush. With a $0.99 coupon for the Adafruit store, it’s effectively free if you’re buying anything at Adafruit anytime soon. Check out the video and the awesome adorable component “muppets”.

Developed On Hackaday: We Have Pixels!

January 12, 2014 by Mathieu Stephan 32 Comments

It has been a while since we kept you informed about the current state of the Mooltipass project. Well, several days ago we finally received the PCBs we got produced at Seeedstudio. Keep in mind that this first version (shown in the picture above) is only meant to check that the chosen components can suit our needs while our mechanical contributors work on their designs. Moreover, we may add empty footprints for our readers that may want to hack the device.

After a few hours of soldering and a few days of coding, we finally got a basic firmware running. The OLED screen is easily readable and has an amazing contrast (the picture doesn’t do it justice). So far we checked all basic functionalities of the on-board components and it’ll still take a few days/weeks to be certain that we can settle with them. We are therefore starting to ship a few platforms to the firmware developers that want to work on the core functions of the Mooltipass. So if you’re an experienced C developer and have some spare time, you may get onboard by contacting me at mathieu[at]hackaday[dot]com or by joining the Mooltipass Google Group.

In a few days we will publish the designs that our mechanical guys came up with and we’ll ask you to let us know which ones are your favorites. Depending on how things will go, we may produce PCBs for several of them to select our final design based on user experience and ease of use. We look forward to hearing your feedback in the comments section below!

Fail Of The Week: Frying FETs With 500mA

January 9, 2014 by Mike Szczys 31 Comments

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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.

3D Printering: Making A Thing With Blender, Part II

January 8, 2014 by Brian Benchoff 49 Comments

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So you have a 3D printer and need to print something of your own design. That’s a problem if you don’t know how to create and edit 3D objects. In this post, we’re continuing our previous misadventures with Blender by making a ‘thing’ torn from a very old book on drafting.

Previously, we’ve made the same part in other 3D design packages. Here’s some links to those other ‘Making a Thing’ posts:

We’ve already done half the work to make a ‘thing’ in Blender, so now it’s time to finish the job. Check out the rest of the tutorial below.

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