Glen Akins shares his latest build the giant three key USB keyboard:

After seeing this giant mechanical keyboard at Adafruit, I decided I had to build my own. Adafruit made theirs out of wood and used one of their Python-compatible microcontroller boards. I wanted a sloped top on my keyboard. I also wanted to check out what was new with Microchip’s USB device stack. I decided to build my keyboard out of aluminum and use a PIC18 microcontroller.

See the full post on his blog here, Photons, Electrons, and Dirt.

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Alvaro Prieto made an IR volume controller and wrote a post on his blog detailing its assembly:

Nui is an IR controlled volume controller for analog audio. It sits between your audio source and speakers and can amplify or reduce the volume using IR commands (and eventually BLE).
Why do I need this?
It all started because I have my trusty Logitech Z-2300 speakers and subwoofer I purchased back around 2004/5. They still work great, but instead of being on my computer, they are used for my TV. Unfortunately, the TV’s line out doesn’t honor the TV’s volume and is always outputting at max volume. Sure, I can get up and change the volume on the speakers themselves, but wouldn’t it be more convenient to do it with the TV remote?!
That’s how the Nui project started. It sits between my TV and my speakers and now I don’t have to get up to change the volume 😀

See the full post on his blog and on GitHub:

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Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:

• Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
• Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
• Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

• Yes, we’ll mail it anywhere in the world!
• Check out how we mail PCBs worldwide video.
• We’ll contact you via Twitter with a coupon code for the PCB drawer.
• Limit one PCB per address per month please.
• Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

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jaeblog published a new build:

I like perfboard, especially the ones with plated trough holes. But I also like SMD components, and more and more fun IC’s are not available in DIP. So a while ago I designed some perfboard with 1.27mm pitch, making some SMD parts like SOIC stuff easy to prototype on it, and also mix THT and SMD stuff.
Looking for a nice little project to build on it, I came across a frequency counter made with 7400 logic, perhaps not the most efficient approach, but a fun one at that. I made a few changed to the design, partly because of some components I already had like the 74HC160 and 4543 (yes, not 7400 but still logic :P) and partly to improve on the design, for example by adding a 10Mhz oscillator instead of a NE555 as the clock source. The current end result looks like this, a case is ordered and a follow up post will be made when the project is nicely tucked away in a case.

More details on Just another electronics blog.

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We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:

• Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
• Facebook PCB Friday. Free PCBs while you wait for the weekend
• Free PCB Sunday, right here on the blog
• Check out how we mail PCBs worldwide

Some stuff:

• Yes, we’ll mail it anywhere in the world!
• Be sure to use a real e-mail in the address field so we can contact you with the coupon.
• Limit one PCB per address per month please.
• Like everything else on this site, PCBs are offered without warranty.
• PCBs are scrap and have no value, due to limited supply it is not possible to replace a board lost in the post

Be the first to comment, subscribe to the RSS feed.

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Good read about class D amplfiers from MAXIM Integrated. Link here (PDF)

A Class D amplifier’s high efficiency makes it ideal for portable and compact high-power applications. Traditional Class D amplifiers require an external lowpass filter to extract the audio signal from the pulse-width-modulated (PWM) output waveform. Many modern Class D amplifiers, however, utilize advanced modulation techniques that, in various applications, both eliminate the need for external filtering and reduce electromagnetic interference (EMI). Eliminating external filters not only reduces board-space requirements, but can also significantly reduce the cost of many portable/compact systems.

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Here’s class D audio amplifier pumping remedy from MAXIM Integrated, power-supply pumping is a problem that occurs when playing low-frequency audio signals through a single-ended output. Link here (PDF)

This application note explains what power-supply pumping is and how it occurs in designs that employ a Class D audio amplifier with single-ended output loads. The article presents three design solutions that will reduce the problem. Mathematical equations show that use of power-supply capacitors greater than 1000µF greatly reduce the phenomenon.

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Dr. Scott M. Baker wrote an article detailing how he converted a Seeburg 3WA wallbox into a media player for his homebuilt audio player:

A bit of background. These Wallboxes were used as remotes in diners and other locations back in the 1950s. You put your nickel, dime, or quarter into the Wallbox, which racks up some credits. Then you select the song you want and the Wallbox sends a signal to the Jukebox, which adds your selection to the queue. Soon thereafter your music is playing through the diner. I’m too young to have experienced these in person when they were state of the art, but I do have an appreciation for antique and retro projects.
A new fad is to convert these wallboxes into remotes for your home audio system, be it Sonos or something else. I have my own homebuilt audio system, basically an augmented Pandora player, so my goal was to use the wallbox to control that.

See the full post on his blog here.

Check out the video after the break.

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Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

• Free PCB Sunday. The classic. Every week, get free PCBs right here on the blog comments
• Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
• Facebook PCB Friday. Free PCBs while you wait for the weekend
• Check out our video on how we mail PCBs worldwide.

Some stuff:

• Yes, we’ll mail it anywhere in the world!
• We’ll contact you via Facebook with a coupon code for the PCB drawer.
• Limit one PCB per address per month, please.
• Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

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