The Importance Of Electrical Safety

March 1, 2017 by Elliot Williams 78 Comments

Everything you do bears some risk of getting you hurt or killed. That’s just the way life is. Some people drown in the bath, and others get kilovolt AC across their heart. Knowing the dangers — how drastic and how likely the are — is the first step toward mitigating them. (We’re not saying that you shouldn’t bathe or play with high voltages.)

This third chapter of an e-book on electronics is a good read. It goes through the physiology of getting shocked (DC is more likely to freeze your muscles, but AC is more likely to fibrillate your heart) and the various scenarios that you should be looking out for. There’s a section on safe practices, and safe circuit design. It’s the basics, but it’s also stuff that we probably should have known when we started messing around with electrons in bulk.

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Octosonar Is 8X Better Than Monosonar

February 25, 2017 by Elliot Williams 29 Comments

The HC-SR04 sonar modules are available for a mere pittance and, with some coaxing, can do a pretty decent job of helping your robot measure the distance to the nearest wall. But when sellers on eBay are shipping these things in ten-packs, why would you stop at mounting just one or two on your ‘bot? Octosonar is a hardware and Arduino software library that’ll get you up and running with up to eight sonar sensors in short order.

Octosonar uses an I2C multiplexer to send the “start” trigger pulses, and an eight-way OR gate to return the “echo” signal back to the host microcontroller. The software library then sends the I2C command to select and trigger a sonar module, and a couple of interrupt routines watch the “echo” line to figure out the time of flight, and thus the distance.

Having two sonars on each side of a rectangular robot allows it move parallel to a wall in a straightforward fashion: steer toward or away from the wall until they match. Watch the video below for a demo of this very simple setup. (But also note where the robot’s 45-degree blind spot is: bump-bump-bump!)

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Ask Hackaday: Bitten By The Crocodile Clip

February 25, 2017 by Elliot Williams 69 Comments

I have a love/hate relationship with the crocodile clip. Nothing is so quick to lash together a few half-baked prototype boards on your desk, but nothing ends up in such a tangle so quickly, either. I love the range of pretty colors that crocodiles come in, as well as the easy ability to just clip on to the side of a PCB, or any old loose wire. But they come loose, they can have intermittent contacts, and we’re not even sure if there is such a thing as a current rating for them.

When [WarriorRocker] wrote in asking what we use instead of crocodile clips, he included a photo that sent a chill down my spine, from a review of some clips on Amazon. I’ve seen this one in real life. And what’s worse is the one with the loose wires that sometimes make contact with the spring-clip body and sometimes not.

After an hour-long debugging session about twelve years ago now, such an intermittent croc caused us to make a lifelong vow. All of our croco-clips have been disassembled, manually inspected, and many of them soldered together. When I buy new ones, I check them all before mixing them in with the known-goods. Even thinking about this now makes me want to pull back their little rubber booties just to make sure. Continue reading “Ask Hackaday: Bitten By The Crocodile Clip” →

Jean-Luc PYcARD Is A Pocketable Python Development Platform

February 23, 2017 by Elliot Williams 11 Comments

It’s a good thing that a ridiculous pun and a screenprint of Jean-Luc Picard on the bottom of the board is enough to qualify for the 2017 Hackaday Sci-Fi Contest, because [bobricius]’s Python-plus-Arduino card and environmental sensor potpourri is very cool.

The PCB design itself is great. It’s got a gigantic LED array, cutout for a wrist strap, and an onboard USB plug so you can program it just by sticking it in your computer; it shows up as a USB mass storage device when you plug it in. The files that show up on the “drive” are Micropython code that you can edit, save, and then run directly on the device. You can hardly beat that for convenience.

And there’s a full complement of sensors: not one but two temperature and humidity sensors, including our recent favorite BME280, which also reads barometric pressure. (We suspect that makes it a tri-corder.) There’s a real-time clock, a buzzer, and some buttons. Want to add more sensors? I2C ports are broken out for your convenience.

Besides having Star Trek flair, this board would give the various educational platforms a run for their money: Micro:bit, we’re looking at you. Very cool indeed!

Pancake-ROM: Eat-only Memory?

February 21, 2017 by Elliot Williams 10 Comments

You can store arbitrary data encoded in binary as a pattern of zeros and ones. What you do to get those zeros and ones is up to you. If you’re in a particularly strange mood, you could even store them as strips of chocolate on Swedish pancakes.

Oddly enough, the possibility of the pancake as digital storage medium was what originally prompted [Michael Kohn] to undertake his similar 2013 project where he encoded his name on a paper wheel. Perhaps wisely, he prototyped on a simpler medium. With that perfected, four years later, it was time to step up to Modified Swedish Pancake Technology (MSPT).

Highlights of the build include trying to optimize the brightness difference between chocolate and pancake. Reducing the amount of sugar in the recipe helps increase contrast by reducing caramelization, naturally. And cotton balls placed under the spinning cardboard platform can help stabilize the spinning breakfast / storage product.

Even so, [Michael] reports that it took multiple tries to get the sixteen bytes (bites?) of success in the video below. The data is stenciled onto the pancake and to our eye is quite distinct. Improvement seems to be more of an issue with better edge detection for the reflectance sensor.

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33C3: Dissecting 3G/4G Phone Modems

February 20, 2017 by Elliot Williams 21 Comments

[LaForge] and [Holger] have been hacking around on cell phones for quite a while now, and this led to them working on the open cellphone at OpenMoko and developing the OsmocomBB GSM SDR software. Now, they are turning their sights on 3G and 4G modems, mostly because they would like to use them inside their own devices, but would also like to make them accessible to the broader hacker community. In this talk at the 33rd Chaos Communications Congress (33C3), they discuss their progress in making this darkest part of the modern smartphone useful for the rest of us.

This talk isn’t about the plug-and-play usage of a modern cell-phone modem, though, it’s about reprogramming it. They pick a Qualcomm chipset because it has a useful DIAG protocol, and in particular choose the Quectel EC20 modem that’s used in the iPhone5, because it makes the DIAG stream easily available.

Our story begins with a firmware upgrade from the manufacturer. They unzipped the files, and were pleasantly surprised to find that it’s actually running Linux, undocumented and without the source code being available. Now, [LaForge] just happens to be the founder of gpl-violations.org and knows a thing or two about getting code from vendors who use Linux without following the terms and conditions. The legal story is long and convoluted, and still ongoing, but they got a lot of code from Quectel, and it looks like they’re trying to make good.

Qualcomm, on the other hand, makes the Linux kernel source code available, if not documented. (This is the source on which Quectel’s code is based.) [LaForge] took over the task of documenting it, and then developing some tools for it — there is more going on than we can cover. All of the results of their work are available on the wiki site, if you’re getting ready to dig in.

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Making Use Of Stellaris/Tiva Real-Time Clock

February 19, 2017 by Elliot Williams 8 Comments

If you’re at all like us, or like [Vadim], you’ve got a stash of development boards in a shoebox on a shelf in your closet. If you’re better organized that we are, it might even be labeled “dev boards”. (Ah well, that’s a project for another day.) Anyway, reach into your box and pull one out, and put it to use. Do something trivial if you need to, but a dev board that’s driving a silly blinker is better than a dev board sitting in the dark.

[Vadim]’s good example to us all is going to serve as the brains for an automated plant watering system. That’s a low-demand application where the microcontroller can spend most of the time sleeping. [Vadim]’s first step, then was to get a real-time clock working with the hibernation mode. There’s working code inline in his blog.

royale-with-cheese-pulp-fiction-2_12-movie-clip-1994-hd-6pkq_ebhxj4mkv-shot0001 — “I don’t know, I didn’t go into Burger King.”

If you use Arduino, you’ll feel at home in the Energia ecosystem. But it’s like ordering a Quarter Pounder with Cheese in Paris: Energia is a Royale with Cheese (YouTube) — it’s the little differences. And maybe that’s the point of the exercise; it’s always a good thing to try out something new, even if it’s only minimally different.

So grab that unused dev board off the shelf, struggle through the unfamiliar development environment and/or toolchain, but remember to keep an eye out for the sweet little differences. The more tools that you’re familiar with, the more solutions will spring to mind when you’re hacking on your next project.