Hacklet 32 – LED Persistence of Vision Displays

Blinking LEDs are good. Moving, spinning things are good too. Put them both together and you get a Persistence of Vision (POV) display. Hackers have been building these displays for years. This week’s Hacklet focuses on some of the best LED POV displays on Hackaday.io!

povtypeWe start with [EduardoZola] and POV as you type, write on the air. [Eduardo] used an Arduino Nano, a pair of 433 MHz radios, some blue LEDs and a motor to create a simple spinning display. A hall effect sensor keeps everything in sync. The entire display is powered by a 500 mAh LiPo battery. The awesome thing about this display is the interactive aspect. The transmitter module connects to a laptop via an on-board USB to serial converter. Typing into any serial terminal sends the text directly to the POV display, where the letters appear to hang in the air.

 

deathringNext up is [boolean] with Silent Orchestra POV aka “Death Ring”. [boolean] didn’t want to just create a POV ring, he wanted a huge 5 foot diameter display for his local Burning Man decompression. Death Ring is an aluminum ring spun by a 3HP motor. A hall effect sensor keeps everything synced up, and keeps Death Ring’s 3 horsepower motor in check. Light is provided by a PixelPusher and WS2812 RGB strips. The system is designed to be interactive, controlled with a Leap Motion controller or a Microsoft Kinect. An MPU-6050 keeps acceleration in check while processing maps video to the LED strip. An Arduino Yun allows the entire system to be controlled via WiFi. [boolean] and his team have taken Death Ring through several revisions. Judging by the quality of their aluminum welding though, they’re on the right track to an awesome end result!

locoHackaday.io power user [Davedarko] has been working on a POV display of a different sort. His Locomatrix is an 8×8 LED matrix which moves in and out on the Z axis. [Dave] originally created Locomatrix as his entry in the 2014 Hackaday Prize. We have to admit this is the first time we’ve seen this sort of display, but the idea is sound. In fact, [Bruce Land] posted in the comments to let [Dave] know that he’d seen a similar technique used with a CRT display back in 1964. We’re betting Dave’s 3D printed gears and LED matrix display will be more robust than a CRT tube slamming two and fro at several hundred pulses per minute!

CPOVFinally, we have Hackaday’s own [Mike Szczys] with CPOV – a Crappy Persistence of Vision display . CPOV is a proof of concept made from upcycled parts which [Mike] threw together in a couple of hours. He grabbed the motor from an old cassette deck, some plywood, perfboard, and of course LEDs to build his display. The processor is an ATtiny2313 running Adafruit’s MiniPOV 3 firmware. The system display doesn’t have a sync input, so [Mike] uses a novel form of Human-in-the-loop PWM control to keep the motor speed in check. CPOV is proof that Hackaday.io isn’t just for polished projects, but for proof of concepts, fails, and just plain research. Even if your project isn’t perfect, documenting it will help you learn from it. It might even inspire someone else to move forward and continue where you left off!

Want more POV goodness? Check out our new POV display list!

Our LEDs are going dim, so that’s about all the time we have for this Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

The Art of Electronics, Third Edition

For any technical domain, there is usually one book held up above all others as the definitive guide. For anyone learning compilers, it’s the dragon book. For general computer science, it’s the first half of [Knuth]’s The Art of Computer Programming. For anyone beginning their studies of electrons and silicon, it’s [Horowitz & Hill]’s The Art of Electronics. This heady tome has graced workbenches and labs the world over and is the definitive resource for anything electronica. The first edition was published in 1980, and the second edition was published in 1989. Now, finally, the third edition is on its way.

The new edition will be released on April 30, 2015 through Cambridge University Press, Amazon, and Adafruit. In fact, [PT] over at Adafruit first announced the new edition on last night’s Ask An Engineer show. [Ladyada] was actually asked to provide a quote for the cover of the new edition, an incredible honor that she is far too humble about.

The latest edition is about 300 pages longer than the second edition. It is thoroughly revised and updated, but still retains the casual charm of the original. Real copies do not exist yet, and the only critical review we have so far is from [Ladyada]. There will be few surprises or disappointments.

Continue reading “The Art of Electronics, Third Edition”

Simple DIY Pen Plotter, Great First CNC Project

[Morten] has been busy recently making a pen plotter. It is a simple and elegant build that he completely designed from the ground up. There are no extra frivolous parts here. The frame is made from laser-cut plexiglass which makes fabrication easy if you have access to a laser cutter. Two NEMA17 motors are responsible for the machine’s movement. One moves the pen carriage back and forth by way of a belt. The other is connected by laser-cut gears to a roller bar, scavenged from an ink jet printer, that moves the paper media forward and aft underneath the pen.

The software chain used here is sort of uncommon compared to other inexpensive DIY CNC machines we see here on Hackaday. [Morten] creates his geometry with Rhino, then uses a plugin called Grasshopper to generate the g-code that controls the machine. That g-code is sent using gRemote to an Arduino flashed with the contraptor.org g-code interpreter. A RAMPS board takes the step and direction signals generated by the Arduino and moves the two stepper motors appropriately.

In typical open-supporting fashion, [Morten] has made his design files freely available for anyone to download. His plotter moves the pen side to side and the paper front to back in order to draw shapes but that’s not the only way a plotter can work. Check out this polar plotter and this one that hangs.

Check out the video after the break…

Continue reading “Simple DIY Pen Plotter, Great First CNC Project”

Trinket EDC Contest – The Deadline Approaches

We’ve got just under 2 days left in the Trinket Everyday Carry Contest. With 79 entries, and t-shirts going to the top 50 entrants, you’ve got pretty darn good odds of getting a shirt out of all of this! The design is great too, [Joe Kim] really did a great job with it!

shirt-low

 

The idea is simple: Build small, pocketable projects which are useful everyday.

We explained everything in our announcement post, and the full rules are available on the contest page. But just as a reminder, the main requirements are

  • The project Must use a Pro Trinket, or a board based on the open source Pro Trinket design.
  • The project must have at least 3 project logs
  • The project must have at least one video
  • The Hackaday.io project must include enough documentation to allow an average hobbyist to replicate the project

There are already some awesome entries vying for the top prize, but who knows – someone may come out of nowhere and walk away with a sweet Rigol ds1054z oscilloscope!

 

The contest deadline is January 3rd, at 12:00 am PDT. The clock is ticking, so stop waiting, and go build something awesome! Good luck to everyone who enters!

TRINKET EDC CONTEST DRAWING #4 RESULTS

The fourth of five random drawings for Hackaday’s Trinket Everyday Carry Contest was held tonight. The winner is [davish] with his entry, Trinket Watch. 

twatch3[davish] loves the current crop of smartwatches, but he wants one he can truly call his own. He’s using the Pro Trinket along with an Adafruit 1.3″ OLED for display duties. That little OLED can show a lot more than just numbers though. [davish] already has Adafruit’s logo demo running on the device. Trinket Watch is going to start out as a simple Arduino coded “dumbwatch”. After the basics of time and date are out of the way, [davish] hopes to add a Bluetooth module and turn Trinket Watch into a full-fledged smartwatch.

trinket-prize-cordwoodWe hope [davish] enjoys his new Cordwood Puzzle from The Hackaday Store. No jigsaws here, cordwood is a puzzle that involves solder! If you get a piece wrong, it’s time to break out that solder wick and fix your mistake. The puzzle is built using the cordwood assembly technique which was popular in the 1950’s and 1960s. We’re not kidding about it being a puzzle either – there are no instructions for this kit! [davish] will know he’s got it right when all 3 LEDs light up.

teensy-3-point-1-in-storeIf you didn’t win this week, all is not lost, you still have one more chance to win a random drawing! Our next drawing will be on 12/30/2014 at 9pm EST. The prize will be a Teensy 3.1 and audio adapter as a prize. To be eligible you need to submit your project as an official entry and publish at least one project log during the week.

The main contest entry window closes on January 2, 2015 – but don’t wait for the last minute! Hit the contest page and build some awesome wearable or pocketable electronics!

The Heathkit Mystery

Heathkit is a company that requires no introduction. From the mid-40s until the 90s, Heathkit was the brand for electronic kits ranging from test equipment, HiFis, amateur radio equipment, computers, to freakin’ robots. Their departure was a tragic loss for generations of engineers, electronic tinkerers and hobbyists who grew up with these excellent and useful kits.

Although Heathkit is dead, 2013 brought an announcement that Heathkit was back in the biz. A Facebook page was launched, a Reddit AMA was held, and the news was that Heathkit would rise from the dead in the first half of 2014. It’s now Christmas, 2014, and there’s no sign of Heathkit anywhere. Adafruit has been keeping a watchful eye on the on the (lack of) developments, and the only surprising thing to report is that there is nothing to report. There has been no new announcement, there are no new products, the “official” Heathkit website hasn’t been updated in a year, and no one knows what’s going on.

Adafruit has decided to dig into the matter, and while they’ve come up with a few items of note, there’s not much to report. A trademark for ‘HEATHKIT’ was filed October 27, 2014 – two months ago. An email was sent to the attorney of record and there has been no response.

This trademark was granted to Heathkit Company, Inc., incorporated in Delaware. Searching for any companies in Delaware using the Heathkit name returns exactly two results: Heathkit Company, Inc., and Heathkit Holdings, Inc.. Adafruit is probably going to pay the $20 to the Delaware Department of State to get the detailed information that includes Heathkit’s tax assessment and tax filing history.

The last bit of information comes from a whois on the heathkit.com domain. The relevant contacts have been emailed, and there are no further details. The Heathkit virtual museum was contacted for information, as was the news editor for ARRL.org. Nobody knows anything, or at least nobody is telling anybody anything.

To date, the only physical evidence of Heathkit’s rebirth is a geocache that was left at Brooklyn Bridge Park, announced during the Reddit AMA. This geocache was recovered by reddit user IFoundTheHeathKit, a throwaway account that had no posts before or since finding the cache. We have no idea what was in that geocache, what the ‘secret passphrase’ or set of instructions was, or if anything ever came of the promise to send one of the first new kits.

So there ‘ya go. A lot of words but no information. If you have any info, the Adafruit crew would like to have a word with you.

Update

The person who found the Heathkit geocache has been found:

 

 

 

 

 

 

 

 

 

The full comment referred to below is,

Hey, person who found the Heathkit geocache here. The secret passcode was an Einstein quote about radio vs wired communication (invisible cats), and they said they’d send me something in early 2014. Never had any communication except through FB, and they haven’t replied to any of my recent messages.

IFoundTheHeathKit might want to email Adafruit with a copy of all the emails.

RISC, Tagged Memory, and Minion Cores

Buy a computing device nowadays, and you’re probably getting something that knows x86 or an ARM. There’s more than one architecture out there for general purpose computing with dual-core MIPS boards available and some very strange silicon that’s making its way into dev boards. lowRISC is the latest endeavour from a few notable silicon designers, able to run Linux ‘well’ and adding a few novel security features that haven’t yet been put together this way before.

There are two interesting features that make the lowRISC notable. The first is tagged memory. This has been used before in older, weirder computers as a sort of metadata for memory. Basically, a few bits of each memory address tag each memory address as executable/non-executable, serve as memory watchpoints, garbage collection, and a lock on every word. New instructions are added to the ISA, allowing these tags to be manipulated, watched, and monitored to prevent the most common single security problem: buffer overflows. It’s an extremely interesting application of tagged memory, and something that isn’t really found in a modern architecture.

The second neat feature of the lowRISC are the minions. These are programmable devices tied to the processor’s I/O that work a lot like a Zynq SOC or the PRU inside the BeagleBone. Basically, they’re used for programmable I/O, implementing SPI/I2C/I2S/SDIO in software, offloading work from the main core, and devices that require very precise timing.

The current goal of the lowRISC team is to develop the hardware on an FPGA, releasing some beta silicon in a year’s time. The first complete chip will be an embedded SOC, hopefully release sometime around late 2016 or early 2017. The ultimate goal is an SOC with a GPU that would be used in mobile phones, set-top boxes, and Raspi and BeagleBone-like dev boards. There are enough people on the team, including [Robert Mullins] and [Alex Bradbury] of the University of Cambridge and the Raspberry Pi, researchers at UC Berkeley, and [Bunnie Huang].

It’s a project still in its infancy, but the features these people are going after are very interesting, and something that just isn’t being done with other platforms.

[Alex Bardbury] gave a talk on lowRISC at ORConf last October. You can check out the presentation here.