Mouse Brains Plus Line Laser Equals Rangefinder

June 17, 2016 by 14 Comments

[Neumi] wrote in with a sweet robotics hack. It’s a 2D laser distance sensor (YouTube) made with a cheap line laser and an optical mouse’s flow-sensor chip used as a low-resolution camera. In one sense, it’s a standard laser-distance-sensor project. But it is clever for a whole bunch of reasons.

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For one, using a mouse sensor as a low-res camera is awesome. It’s designed to read from a standard red LED, so the sensitivity is in just the right ballpark for use with a line laser. It returns a 30×30 pixel greyscale image, which is just about the right amount of data for a low-end microcontroller to handle and keep up with the framerate without resorting to coding tricks.

It’s also no coincidence that these sensors are available with lenses built in, for relatively cheap, on eBay. Apparently the quadcopter gurus use them as if they were mice to visually track their quad’s motion. Hacker spillover!

Detecting the laser line as it reflects off of whatever objects are lying on [Neumi]’s floor could also possibly prove difficult, and might produce false readings in the presence of background illumination. So [Neumi] takes two readings with the camera — one with the laser on and one with it off — and differences them. Done fast enough, this should reduce any non-laser sources down to the sensor’s noise floor. Finally, there’s some thresholding and averaging going on behind the scenes that help make everything work out right. The code is up on GitHub.

Not a bad build for a 2D laser distance system on a budget. If you want to shell out a bit more money, and are into a seriously involved build, this is probably the slickest we’ve seen in a long time. And if you’re thinking that you’ve heard of [Neumi] before, you’re right: we featured this 405mm laser PCB exposer / burner CNC machine just a few months ago.

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Fail Of The Week: Where’s Me Jumper?

June 17, 2016 by 64 Comments

Just in case you imagine that those of us who write for Hackaday are among the elite of engineering talent who never put a foot wrong and whose benches see a succession of perfectly executed builds and amazing hacks, let me disabuse you of that notion with an ignominious failure of my own.

I was building an electronic kit, a few weeks ago. It’s a modular design with multiple cards on a backplane, though since in due course you’ll see a review of it here I’ll save you its details until that moment. In my several decades of electronic endeavours I have built many kits, so this one as a through-hole design on the standard 0.1″ pitch should have presented me with no issues at all. Sadly though it didn’t work out that way.

Things started to go wrong towards the end of the build, I noticed that the temperature regulator on my soldering iron had failed at some point during its construction. Most of it had thus been soldered at a worryingly high temperature, so I was faced with a lot of solder joints to go over and rework in case any of them had been rendered dry by the excessive heat.

In due course when I powered my completed kit up, nothing worked. It must have been the extra heat, I thought, so out came the desolder braid and yet again I reworked the whole kit. Still no joy. Firing up my oscilloscope I could see things happening on its clock and data lines so there was hope, but this wasn’t a kit that was responding to therapy. A long conversation with the (very patient) kit manufacturer left me having followed up a selection of avenues, all to no avail. By this time a couple of weeks of on-and-off diagnostics had come and gone, and I was getting desperate. Somehow I’d cooked this thing with my faulty iron, and there was no way to find the culprit.

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Master’s UAV Project Takes Flight

June 17, 2016 by 7 Comments

Pushing the maker envelope all the way to the Master level, [Przemyslaw Brudny], [Marek Ulita], and [Maciej Olejnik] from the Politechnika Wroclawska in Poland packed a UAV full of custom sensor boards for their thesis project.

The Skywalker X-8 FPV drone underwent extensive modifications to accommodate the embedded systems as well as upgrading the chassis with carbon glass to withstand the high load and speeds they would need to perform their tests. The ailerons were customized for finer control of the drone. But for our money, it’s all the board design that supports those sensors which is really fun to delve into.

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A Slide Viewer Makes An Excellent Case For An OLED Project

June 17, 2016 by 17 Comments

Sometimes when browsing the websites of our global hackspace community you notice a project that’s attractive not necessarily because of what it does or its technology but because of its presentation. So it is with the subject of this article, [Kris] needed a house temperature monitor and found a 1960s slide viewer made an excellent choice for its housing.

The monitor itself is a fairly straightforward Arduino build using a couple of DS18B20 1-wire temperature sensors and a real-time-clock module and displaying their readings on a small OLED screen. Its code can be found on this mailing list thread if you are interested. The display presented a problem as it needed to be reasonably large, yet fairly dim so it could be read at night without being bright enough to interrupt sleep.

A variety of projection techniques were tried, involving lenses from a projection clock, a magnifying glass, and a Google Cardboard clone. Sadly none of these lenses had the required focal length. Eventually the slide viewer was chosen because it was pointed out that the OLED screen was about the same size as a photographic slide.

Slide viewers are part of the familiar ephemera of the analog era that most people over 60 may still have taking up drawer space somewhere but may well be completely alien to anyone under about 30. They were a magnification system packaged up into a console usually styled to look something like a small portable TV of the day, and different models had built-in battery lights, or collected ambient light with a mirror. The screen was usually a large rectangular lens about 100mm(4″) diagonal.

[Kris]’s Vistarama slide viewer came via eBay. It’s not the smallest of viewers, other models folded their light paths with mirrors, however the extra space meant that the Arduino fit easily. The OLED was placed where the slide would go, and its display appeared at just the right magnification and brightness. Job done, and looking rather stylish!

We’ve not featured a slide viewer before here at Hackaday, though we did recently feature a similar hack on an Ikea toy projector. We have however featured more than one digital conversion on a classic slide projector using LCD screens in place of the slide.

Via Robots and Dinosaurs makerspace, Sydney.

Hackaday Prize Entry: Electronic, Visual Harmonicas

June 16, 2016 by 5 Comments

[sholnkin] is tasked with teaching a kindergarten class how to play a musical instrument. No, not those cheap plastic recorders. [shlonkin] is teaching kindergarteners how to play the only instrument that both blows and sucks: the harmonica.

Unlike a classroom of kids with plastic recorders, where the fingering is either right or it isn’t, [shlonkin] needs to teach kids to put their mouth over the right hole, and suck or blow to produce a note. The classroom has a poster laying out the notes on the harmonica, but they needed something better. [shlonkin] envisioned a large illuminated sign that lit up in different colors, and could play the displayed notes with a speaker.

The high-level design for this project includes a Teensy 3.2 with the Audio Adapter breakout driving a small audio amp. The Teensy also controls a bunch of LEDs mounted inside a wooden case. The layout of these LEDs went surprisingly well, and it’s rare to find a backlit panel that is lit this evenly.

As a classroom musical teaching aid, this type of device has been around for decades – deep in the recesses of band rooms in schools across the world, you can find old Wurlitzer pianos with devices that aren’t much different from this simple device. It’s a pedagogical method that worked back then, and should work now.

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No Frame Buffer For FPGA VGA Graphics

June 16, 2016 by 8 Comments

Usually, when you think of driving a VGA–in software or hardware–you think of using a frame buffer. The frame buffer is usually dual port RAM. One hardware or software process fills in the RAM and another process pulls the data out at the right rate and sends it to the VGA display (usually through a digital to analog converter).

[Connor Archard] and [Noah Levy] wanted to do some music processing with a DE2-115 FPGA board. To drive the VGA display, they took a novel approach. Instead of a frame buffer, they use the FPGA to compute each pixel’s data in real-time.

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Reverse Engineering A Nissan Leaf Battery Pack

June 16, 2016 by 36 Comments

Batteries wear out. If you are an electric vehicle enthusiast, it’s a certainty that at some time in your not-too-distant future there will be a point at which your vehicle’s batteries have reached the end of their lives and will need to be replaced. If you have bought a new electric vehicle the chances are that you will be signed up to a leasing deal with the manufacturer which will take care of this replacement, but if you have an older vehicle this is likely to be an expensive moment.

Fortunately there is a tempting solution. As an increasing number of electric vehicles from large manufacturers appear on our roads, a corresponding number of them have become available on the scrap market from accident damage. It is thus not impossible to secure a fairly new lithium-ion battery pack from a modern electric car, and for a significantly lower price than you would pay for new cells. As always though, there is a snag. Such packs are designed only for the cars they came with, and have proprietary connectors and protocols with which they communicate with their host vehicle. Fitting them to another car is thus not a task for the faint hearted.

Hackaday reader [Wolf] has an electric truck, a Solectria E10. It has a set of elderly lead-acid batteries and would benefit hugely from an upgrade to lithium-ion. He secured a battery pack from a 2013 Nissan Leaf electric car, and he set about reverse engineering its battery management system (BMS). The Solectria will use a different battery configuration from the Leaf, so while he would like to use the Leaf’s BMS, he has had to reverse engineer its protocols so that he can replace its Nissan microcontroller with one of his own.

His description of the reverse engineering process is lengthy and detailed, and with its many photos and videos is well worth a read. He employs some clever techniques, such as making his own hardware simulation of a Li-ion cell so that he can supply the BMS known values that he can then sniff from the serial data stream.

We’ve covered quite a few EV batteries here at Hackaday. Quite recently we even covered another truck conversion using Leaf batteries, and last year we featured a Leaf battery teardown. We’ve not restricted ourselves to Nissan though, for example here’s a similar process with a Tesla Model S pack.