LED Matrix Failure And Vindication

September 7, 2015 by Elliot Williams 12 Comments

If necessity is the mother of invention, what’s failure the mother of? Improvement? Anyway, [prpplague]’s second version of his roll-up 70×30 RGB LED display looks a lot better and more reliable than the first, and that’s precisely due to “failing”.

Sometimes you design the hardware around the software, and sometimes vice-versa. It’s all about the balance of pain. [prpplague] initially wired the strips together in a consistently left-to-right raster arrangement to make the coding easier, but this means long wires on the backside of the fabric returning from the right side back to the start again at the left. These long wires snagged on stuff, and pulled the solder connections apart.

The fix? Alternate rows of left-to-right with right-to-left to minimize wiring and make nice, robust connectors for the ends, and a much more elegant implementation at the expense of more complicated software to drive the device. (Alternating rows have to be flipped horizontally, so this means custom driver routines.)

The second gremlin was that the interfacing board that [prpplague] was using didn’t have enough current sourcing capability on the SPI lines, and he discovered that he couldn’t communicate reliably with the strings if the first pixel was more than 24″ of wire away from the board. Once the signal got to the first pixel, though, everything was fine. [prpplague] figured out that the RGB LEDs themselves had more drive capability than the SPI source.

The solution? Add a single pixel at the front of the chain to buffer the SPI lines and serve as a bonus status indicator. Cute.

We’d hardly call these “fails”, but rather “learning experiences”. Anyway, here’s two design “mistakes” that we won’t make when making a roll-up flexible pixel display. Thanks [prpplague].

Better Batteries For Electronic Gadgets

September 6, 2015 by Brian Benchoff 46 Comments

We’re not using 9 Volt batteries to power our projects anymore; the world of hobby electronics has moved on to cheap LiPo batteries for most of our mobile power storage. LiPos aren’t the best solution, evidenced by hundreds of YouTube videos of exploding batteries, and more than a few puffy cells in our junk drawer. The solution? LiFePO4, or lithium iron phosphate cells. They’re a safer chemistry, they have low self discharge, and have more recharge than other chemistry of lithium cells.

LiFePO4 cells aren’t easy to deal with if you’re working with breadboard electronics, though. Most of that is because there aren’t many breakout boards for these cells. [Patrick] is working on changing that with his LiFePO4werd USB charger.

The concept is simple: use an off-the-shelf part for LiFePO4 batteries – in this case an MCP73123 – and make a board that charges the batteries with a USB port. It’s exactly the same idea as the many USB LiPo chargers out there, only this one uses a better battery chemistry.

[Patrick] is using a 550mAh battery for this project, but there’s no reason why it couldn’t be upgraded to a 18650-sized cell with more than 2000mAh stuffed inside. Add a boost converter to the circuit, and he’ll have the perfect power source for every portable electronics project imaginable.

How To Make A Hugo (Base)

September 5, 2015 by Al Williams 25 Comments

A lot of hackers like science fiction. If you aren’t one of them, you might not know that the Hugo is a prestigious science fiction award handed out at the World Science Fiction Convention every year. The statue looks like a rocket ship, but every year the base the rocket ship rests on is different. Kinetic sculptor [gfish] realized the convention would be in Spokane (his hometown and near his current residence) and decided to enter the competition to create the bases. He won, so the 2015 Hugos all have [gfish’s] bases on them and it’s pretty neat that he’s shared the process he used to make them.

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Scanning Electron Microscope Images And Animations Pulled By Impressive Teensy LC Setup

September 5, 2015 by Dan Maloney 29 Comments

When you’ve got a scanning electron microscope sitting around, you’re going to find ways to push the awesome envelope. [Ben Krasnow] is upping his SEM game with a new rig to improve image capture (video link) and more easily create animated GIFs and videos.

The color scheme of the SEM housing gives away its 80s vintage, and the height of image capture technology back then was a Polaroid camera mounted over the instrument’s CRT. No other video output was provided, so [Ben] dug into the blueprints and probed around till he found the high-resolution slow scan signal.

To make his Teensy-LC happy, he used a few op-amps to condition the analog signal for the greatest resolution and split out the digital sync signals, which he fed into the analog and digital ports respectively. [Ben] then goes into a great deal of useful detail on how he got the video data encoded and sent over USB for frame capture and GIF generation. Reading the ADC quickly without jitter and balancing data collection with transmission were tricky, but he has established a rock-solid system for it.

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Slimline USB Charger For Tiny Ham Radios

September 5, 2015 by Dan Maloney 12 Comments

The recent trend to smaller and smaller handy talkie (HT) transceivers is approaching the limits of the human interface. Sure, engineers could probably continue shrinking the Baofeng and Wouxun HTs further, but pretty soon they’ll just be too small to operate. And it’s getting to the point where the accessories, particularly the battery charging trays, are getting bulkier than the radios. With that in mind, [Mads Hobye] decided to slim down his backpacking loadout by designing a slimline USB charger for his Baofeng HT.

Lacking an external charging jack but sporting a 3.7 volt battery pack with exposed charging terminals on the rear, [Mads] cleverly capitalized on the belt clip to apply spring tension to a laser-cut acrylic plate. A pair of bolts makes contact with the charging terminals on the battery pack, and the attached USB cable allows him to connect to an off-the-shelf 3.7 volt LiPo USB charger, easy to come by in multicopter circles. YMMV – the Baofeng UV-5R dual-band HT sitting on my desk has a 7.4 volt battery pack, so I’d have to make some adjustments. But you have to applaud the simplicity of the build and its packability relative to the OEM charging setup.

This isn’t the first time we’ve seen [Mads] on Hackaday. He and the FabLab RUC crew were recently featured with their open-source robotic arm.

Demonstrating Science At Harvard University

September 4, 2015 by Mike Szczys 18 Comments

What if there was a job where you built, serviced, and prepared science demonstrations? This means showing off everything from principles of physics, to electronic theory, to chemistry and biology. Would you grab onto that job with both hands and never let go? That was my reaction when I met [Dan Rosenberg] who is a Science Lecture Demonstrator at Harvard University. He gave me a tour of the Science Center, as well as a behind the scenes look at some of the apparatus he works with and has built.

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Experimental Theater Helps Field Test Haptic Navigation Device

September 4, 2015 by Dan Maloney 7 Comments

The “absorbed device user” meme, like someone following Google Maps on a smart phone so closely that they walk out into traffic, is becoming all too common. Not only can an interface that requires face time be a hazard to your health in traffic, it’s also not particularly useful to the visually impaired. Haptic interfaces can help the sighted and the visually impaired alike, but a smart phone really only has one haptic trick – vibration. But a Yale engineer has developed a 3D printed shape-shifting navigation tool that could be a haptics game changer.

Dubbed the Animotus by inventor [Ad Spiers], the device is a hand-held cube split into two layers. The upper layer can swivel left or right and extend or retract, giving the user both tactile and visual clues as to which direction to walk and how far to the goal. For a field test of the device, [Ad] teamed up with a London theater group in an interactive production of the play “Flatland”, the bulk of which was staged in an old church in total darkness. As you can see in the night-vision video after the break, audience members wearing tracking devices were each given an Animotus to allow them to navigate through the interactive sets. The tracking data indicated users quickly adapted to navigation in the dark while using the Animotus, and some became so attached to their device that they were upset by the ending of the play, which involved its mock confiscation and destruction.

Performing art applications aside, there’s plenty of potential for haptics with more than one degree of freedom. Imagine a Bluetooth interface to the aforementioned Google Maps, or an electronic seeing-eye dog that guides a user around obstacles using an Animotus and a camera. There’s still plenty of utility in traditional haptics, though, as this Hackaday Prize semi-finalist shows.

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