Easy DIY Telemetry Goes The Distance

June 18, 2016 by Elliot Williams 11 Comments

[Paweł Spychalski] wrote in to tell us about some experiments he’s been doing, using cheap 433 MHz HC-12 radio units as a telemetry radio for his quadcopter.

In this blog post, he goes over the simple AT command set, and some of the limitations of the HC-12 part. Then he takes it out for a spin on his quadcopter, and finds out that his setup is good for 450 meters in an open field. Finally, he ties the radio into his quad’s telemetry system and tethers the other end to his cellphone through a Bluetooth unit for a sweet end-to-end system that only set him back around $20 and works as far out as 700 meters.

The secrets to [Paweł]’s success seem to be some hand-made antennas and keeping the baud rate down to a reasonable 9600 baud. We wonder if there’s room (or reason?) for improvement using a directional antenna on the ground. What say you, Hackaday Antenna Jockeys?

Also check out this very similar build where an ESP8266 replaces the Bluetooth module. And stashes it all inside a nice wooden box! Nice work all around.

Marvelous MIDI Button Box

June 18, 2016 by Elliot Williams 1 Comment

Most DJ tools are just ripe for DIY rework. Everything at least speaks MIDI, and the firmware side of the equation that makes a physical interface for your laptop can be downloaded and flashed with minimal effort. And this means that there’s no time better than the present to wire up a ton of buttons to a Teensy and call it a controller.

[UmamiFish]’s build goes the extra mile, though, with a nice laser-cut box and holes for display LEDs as well as the 22 arcade buttons that are packed tightly into the enclosure. A 74HC595 shift-register IC handles the LEDs, but there’s no getting around a bunch of wiring in a build like this. It pays to be neat, and using ribbon cable helps keep some of the chaos under control.

Browsing around Instructables will turn up myriad similar controllers, should the exact configuration of this one not suit your needs. And if you want something with a little more of the real-disk feel, have a look at this controller that uses hard disk platters, or this log of a timecode-vinyl-to-MIDI build.

Ask Hackaday: Whatever Happened To LED Light Sensors?

June 17, 2016 by Elliot Williams 17 Comments

If you’re a long-time Hackaday reader like we are, you’ll certainly remember a rash of projects from around ten years ago that all (mis-)used an LED as a light sensor. The idea wasn’t new, but somehow it made the rounds and insinuated itself into our collective minds. Around the same time, a cryptographic cipher with an exceptionally small memory footprint was also showing up in hacker projects: TEA (Tiny Encryption Algorithm).

This old project by [Marcin Bojanczyk], [Chris Danis], and [Brian Rogan] combines both the LED-as-light-sensor meme and TEA to make a door-entry keyfob that works over visible light. And they do so using almost nothing — a few LEDs and just over 2Kb of code. It’s pretty sweet.

Which brings us to the question: where are they (LED-sensors and TEA) now?

LED-as-light-sensor was just cool. We certainly loved the idea back in 2006. But [Forrest Mims] had been using the phenomenon for decades back then. It certainly makes sense when you’re trying to squeeze as much as possible out of as little as possible, or when budget is a main concern and you just can’t afford an extra photodiode.

But our own experience with LEDs as light sensors is that the results are extremely variable across different LEDs. Code that works with water-clear red LEDs might not work with the ones that come in red-tinted plastic, for instance. Is that why they went extinct?
Similarly, the TEA family of ciphers showed up in a bunch of projects around this time, from the badge for the HOPE conference in 2010 to a widely used RFM12B radio library. There are a couple of attacks on XXTEA, but they only affect reduced-round versions of the cipher, and rely on a tremendous amount of intercepted data — more than we’d see in a home-automation network over years.

Over the last five years or so, there’s been a lot more Internet of Things, which means using standard Internet-style encryption methods (AES and so on) that are widespread on non-memory-constrained computers. Is that what happened to XXTEA?

Anyway, we got tipped off to a project that combined a few of our favorite (old) ideas in one, so we thought that we’d share. Thanks [Blue Smoke] for the walk down memory lane. Any of you out there keeping the flame(s) alive? Have you used sensing LEDs or XXTEA? Are those projects still going, or do you have any future projects planned with these tricks still up your sleeve? Let us know in the comments below.

Mouse Brains Plus Line Laser Equals Rangefinder

June 17, 2016 by Elliot Williams 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.

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.

Continue reading “Mouse Brains Plus Line Laser Equals Rangefinder” →

Beautiful Cardboard Robot Build

June 16, 2016 by Elliot Williams 16 Comments

[Miloslav Stibor] may have built Mimobot 2.1 out of cardboard so that it’s not very heavy, but the robot is absolutely no lightweight. Read through his logs (in Czech, or in translation) and you’ll see what we mean.

Our favorite feature is the recharging dock and docking connectors, made respectively out of spring-loaded rivet ferrules and copper-tape-covered cardboard. The video found on that page is also absolutely brilliant: watch in awe as it climbs over children’s books, pulls a wooden train, or scales a mountain of pillows.

We wrote [Miloslav] and asked about the continuous-rotation servos, because they ran so smoothly at low speeds. He replaced the potentiometer with a pair of “carefully matched” 2.2 k resistors, and drives them with a PWM signal. Sounds easy, and obviously works very well. We were always under the impression that it was a little bit more complicated to get proportional control of hobby servos. We’ll have to experiment.

The wheels and lightweight frame (made of “military grade” cardboard — saturated with a wood/paper glue) make it entirely capable in living-room environments covered in cables or rugs, which is something we can’t say about our purchased vacuum-cleaner-bot. And the cell-phone remote interface that lets him control the onboard camera and its elevation and lighting. Driving the thing around with the phone control looks fun.

In short, if you build small robots, give this one a look. Something very much like this is now on our short must-build list. And we can’t wait to see Mimobot v3!

Robot Bites Man!

June 15, 2016 by Elliot Williams 49 Comments

The old newspaper saying holds that a dog biting a man isn’t news, but “Man Bites Dog” is a stellar headline. So instead of focusing on the usual human-on-small-robot ~~torture~~ experiments as we usually do, we bring you “The First Law“, an art piece by [Alex Reben].

[Alex] built a robot that “intentionally” defies Asimov’s First Law: doing no harm to humans. A human puts its little pink finger in the slot, is sensed, and a robot arm with a needle comes down and smashes through the meatbag’s puny fleshy appendage. Or maybe it doesn’t — it’s got a randomization routine that can be said to be “choosing” to prick you or not.

Yeah, the pin-prick is trivial, and yeah, the robot is not really deciding, but the point of the ‘bot is to get people talking. In a world where killer robots are not (yet, explicitly) against the Geneva Convention, soon we’re going to be facing this problem for real. If we need robot-art that makes literary references to get us thinking about these issues, so be it.

Of course, you don’t need to wait until there’s moral consensus to build your own terribly dangerous “robots” at home. How about an automated flamethrower or a knife-wielding tentacle? Or maybe this once, we’ll say that it makes more sense to just sit back and read about other folks doing it.

Via [Fast Company]. Thanks [fishocks367] for the tip!

Premier Farnell Sold To Swiss Firm

June 15, 2016 by Elliot Williams 34 Comments

According to this article in the Guardian, Premier Farnell, the electronics parts distributor who is also a UK manufacturer of the Raspberry Pi, is going to be sold to Dätwyler. Their share price immediately rose 50%, closing at just under the Swiss firm’s offer price.

Farnell itself had been on a binge, according to Wikipedia anyway, buying up electronics distributorships in Poland, India, and the US. In 2009, they bought Cadsoft, the makers of Eagle CAD software. Now they’re being sold to another distributor.

Bloomberg writes this up as being just more consolidation in an already consolidating market. What any of this will mean for the hacker on the street is anyone’s guess, but we’re putting our money on it amounting to nearly nothing. But still, now’s the time to stock up on your genuine UK-owned, made-in-UK Pis before they become Swiss-owned and made who knows where.