Hacklet 95 – More Pi Zero Contest Entries

We’re well into the second week of the Hackaday and Adafruit ultimate team-up: The Raspberry Pi Zero Contest. The entries have been flying in! As of Thursday evening, we have 70 projects vying for one of 10 Raspberry Pi Zeros, and one of three $100 gift certificates to The Hackaday Store. This week on The Hacklet, we’re going to take a look at a few more contest entries.

blueberryWe start with [Sean Hodgins] and Blueberry Zero – Keep your Pi in your Pocket. [Sean] can’t leave home without his Raspberry Pi Zero. Carrying all the cables, adapters, and accessories required to power up a tiny Linux computer can be a chore though. He’s created a solution to simplify all that with Blueberry Zero. This custom PCB hat contains an HC-05 style Bluetooth module connected to the Pi’s console port. Serial alone doesn’t make for a standalone Pi, so [Sean] added a LiPo battery and charger chip. A switching power supply boosts the 4.2 V LiPo output up to the 5 V required for the Pi. Now when [Sean] just has to hack out some python code, all he needs to do is open a Bluetooth connection from a cell phone, tablet, or computer.

pcpower[Doihaveto] is using his Pi Zero to manage a desktop PC. PC Power allows him to not only turn his computer on or off, but to disconnect the mains power completely. [Doihaveto’s] PC does have Wake On Lan, but he’s run into problems when the system has failed. His Pi provides an extra layer of protection in case things don’t wake up as expected. The board contains two optoisolated connections to a host PC. One is the power switch output, the other is the power LED input. If all else fails, PC Power also can control a solid state relay to completely isolate the computer from mains power. PC Power uses a web interface created with Python using the flask web framework.

pifoldNext up is [tomwsmf] with PiFold. Like [Sean] up above, [tomwsmf] can’t leave home without his Pi Zero. Rather than hacking code though, [tomwsmf] is serving up media. PiFold is a wallet containing a Pi Zero powered server. The Anyfesto software package runs on the Pi, serving up songs and files via WiFi. Audio is also transmitted on 88.1 MHz FM via PiFM. A 2500 mAh battery pack coupled with a boost converter keeps PiFold humming away. When the battery needs a charge, [tomwsmf] can use a small solar panel to top up the battery while staying green.



retrorobotFinally, we have [Fredrik J] with Retrofit Robot. The 1980’s were a golden age of toy robots from Japan. Tomy, Nikko, and a few other companies created devices like Omnibot, which were ahead of their time. [Fredrick] still has his vintage Nikko RC-ROBOT, but it has long since ceased to function. The Pi Zero presents a perfect opportunity to give the little guy a new lease on life. [Fredrik’s] goal is to keep the RC-ROBOT’s original look while giving him new functions. The old DC motors are being replaced with closed loop servos. The servos will be controlled by an Adafruit 16 channel servo driver board. The next step for Retrofit Robot is a big 6000 mAh battery. We can’t wait to see how this one turns out!

If you want to see more entrants to Hackaday and Adafruit’s Pi Zero contest, check out the submissions list! If you don’t see your project on that list, you don’t have to contact me, just submit it to the Pi Zero Contest! That’s it for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

Embed with Elliot: Audio Playback with Direct Digital Synthesis

Direct-digital synthesis (DDS) is a sample-playback technique that is useful for adding a little bit of audio to your projects without additional hardware. Want your robot to say ouch when it bumps into a wall? Or to play a flute solo? Of course, you could just buy a cheap WAV playback shield or module and write all of the samples to an SD card. Then you wouldn’t have to know anything about how microcontrollers can produce pitched audio, and could just skip the rest of this column and get on with your life.

Harmonic distortion down ~45db on an Arduino
~45db signal to noise ratio from an Arduino

But that’s not the way we roll. We’re going to embed the audio data in the code, and play it back with absolutely minimal additional hardware. And we’ll also gain control of the process. If you want to play your samples faster or slower, or add a tremolo effect, you’re going to want to take things into your own hands. We’re going to show you how to take a single sample of data and play it back at any pitch you’d like. DDS, oversimplified, is a way to make these modifications in pitch possible even though you’re using a fixed-frequency clock.

The same techniques used here can turn your microcontroller into a cheap and cheerful function generator that’s good for under a hundred kilohertz using PWM, and much faster with a better analog output. Hackaday’s own [Bil Herd] has a nice video post about the hardware side of digital signal generation that makes a great companion to this one if you’d like to go that route. But we’ll be focusing here on audio, because it’s easier, hands-on, and fun.

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Clearly the Best Way to Organize SMD Parts

Have some plexiglas (acrylic) leftovers lying around? Well, they could be put to good use in making this SMD organizer. It comes in handy if you deal with a lot of SMD components in your work. No longer will you waste your time trying to find a 15K 1206 resistor, or that BAS85 diode… or any other component you can think of soldering on the PCB. The basic idea is fairly straightforword, which helped keep this short.

2SMD resistors are packed in thick paper tapes that don’t bend easily, and thus need larger containers than other components, which are packed mainly in flexible PE tapes. The first version of this organizer was built with a 96mm diameter space for resistors and 63mm diameter for other components, but it seems that there is no need for such large compartments. If I were to make it again, I would probably scale everything down to about 80% of it’s current size.

The best way to join all plexiglass parts is to use four M4 threaded rods. There is also a 1.5mm steel rod which holds SMD tape ends in place and helps to un-stick the transparent tape which covers the components. At the top of the organizer there is a notch for paper, used for components labels. Most SMD components are packed in 8mm wide tapes, making the optimal compartment width 10mm. It is not easy to cut the 10mm thick acrylic and get a neat edge – instead, you could use more layers of thin sheets to make the spacers. Using 5mm acrylic you can combine more layers for any width of tape, which contains wider components, like SMD integrated circuits. The only thing that you have to be careful about, is to keep the distance between the thin steel rod and acrylic, which is marked as “2-4mm” on the drawing. It is good if this space is just a few tenths of a millimeter wider than the thickness of SMD tapes.

smd_orthoThe CorelDraw file that can be used for laser cutting the acrylic parts, is available for download. If you scale the profiles, don’t forget to readjust the hole diameters and some other dimensions which have to remain intact. If you have 5mm acrylic pieces, you should probably use two layers of acrylic for every tape (red parts on the drawing). The barrier layers would be made of thin acrylic — for instance 2mm (the blue parts). Edge layers (green) are once again 5mm thick, and there are also the end pieces (yellow), glued to the previous borders and used to “round up” the whole construction and to protect your hands from the threaded rods and nuts.

While you’re building this for your bench, make a vacuum picking tool for SMDs out of a dispensing syringe with a thick needle. It’s a common trick for hackers to use an aquarium air pump, just turn the compressor unit by 180°, so that it creates vacuum instead of blowing the air outside. This process is described by R&TPreppers in the video below.

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Digital Communications 1830s Style

We think of digital communications as a modern invention. But the reality is that semaphores, smoke signals, and Aldis lamps are all types of digital communication. While telegraphs are not as old as smoke signals, they, too, are a digital mode. The problem with all of these is that they require the operator to learn some kind of code. People don’t like to learn code because it is difficult, and employers don’t like to pay high wages to trained operators.

In the late 1830s, a man named William Cooke proposed a complex telegraph to a railway company. The company didn’t care for it and asked for something simpler. The railway didn’t like that either, so Cooke joined up with Charles Wheatstone and patented something that was a cross between a telegraph and a Ouija board.

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We’re Hiring

Hackaday has been expanding into all kinds of new areas. We find ourselves stretched a bit thin and it’s time to ask for help. Want to lend a hand while making some extra dough to plow back into your projects? These are work-from-home (or wherever you like) positions and we’re looking for awesome, motivated people to help guide Hackaday forward!

Contributors are hired as private contractors and paid for each post. You should have the technical expertise to understand the projects you write about, and a passion for the wide range of topics we feature. If you’re interested, please email our jobs line, and include:

  • Details about your background (education, employment, etc.) that make you a valuable addition to the team
  • Links to your blog/project posts/etc. which have been published on the Internet
  • One example post written in the voice of Hackaday. Include a banner image, at least 150 words, the link to the project, and any in-links to related and relevant Hackaday features

What are you waiting for? Ladies and Gentlemen, start your applications!

The Triumph of Open Design and the Birth of a FormLabs Aftermarket

Whilst designing hardware, it’s easy to shut the doors, close the blinds, and bury ourselves deeply into an after-hours design session. Although it’s tempting to fly solo, it’s likely that we’ll encounter bugs that others have handled, or perhaps we’ll realize that we forgot to add a handy feature that someone else could’ve noticed before we sent the darned PCB files out for fab. All that said, if we probe the community around us and ask for feedback, we can produce a project that’s far more functional and feature-complete in less time than if we were to design solo. Who knows? With enough eyes giving feedback on your project, maybe others will get excited enough to want one for themselves! [Andrew Werby] and [Zak Timan] on the FormLabs forums did just that: through months of iterative design and discussion on the FormLabs forums, they’ve created the first 3rd party glass resin tank that’s altogether sturdier, longer-lasting, more scratch-resistant, and less distorting than the original resin tank. And guess what? After months of trials through a few brave customers, you too can be the proud owner such a tank as they’re now up for sale on [Zak’s] website.
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Learn Resin Casting Techniques: Duplicating Plastic Parts

Resin casting lets you produce parts that would be otherwise impossible to make without a full CNC and injection molding set-up. It costs about as much as a 3d printer, 300 to 600 US dollars, to get a good set-up going. This is for raw material, resin, dye, pressure chamber, and an optional vacuum degassing set-up. A good resin casting set-up will let you produce parts which are stronger than injection molding, and with phenomenal accuracy, temperature resistance, and strength. I will be covering various techniques from the simple to advanced for using resin casting from a hacker’s perspective.

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