Author: Al Williams

4504 Articles

Linux Fu: Counter Rotate Keys!

June 1, 2018 by 22 Comments

If you’ve done anything with a modern Linux system — including most variants for the Raspberry Pi — you probably know about sudo. This typically allows an authorized user to elevate themselves to superuser status to do things.

However, there is a problem. If you have sudo access, you can do anything — at least, anything the sudoers file allows you to do. But what about extremely critical operations? We’ve all seen the movies where launching the nuclear missile requires two keys counter-rotated at the same time and third firing key. Is there an equivalent for Linux systems?

It isn’t exactly a counter-rotating key, but the sudo_pair project — a prelease open-source project from Square — gives you something similar. The project is a plugin for sudo that allows you to have another user authorize a sudo request. Not only do they authorize it, but they get to see what is happening, and even abort it if something bad is happening.

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Hacking A Fitness Tracker

May 29, 2018 by 20 Comments

When [rbaron] started a new job, he got a goodie bag. The contents included a cheap fitness tracker bracelet that used Bluetooth LE. Since this is Hackaday, you can probably guess what happened next: hacking ensued.

For something cheap enough to give away, [rbaron] claims it cost $10, the device has quite a bit in it. In the very tiny package, there is an OLED display, a battery, a vibration motor, and a Nordic 32-bit ARM with BLE. The FCC ID was key to identifying the device. Opening the case, which was glued down, was pretty difficult, but doable with a hair dryer and a knife.

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Ham Radio On $100 Or Less

May 28, 2018 by 63 Comments

There are a lot of reasons to get a ham radio license, and if you are one of those that think ham radio is dead you can probably skip this post. However, if you have been interested, but didn’t want to drop a lot of money on a station, [KE6MT] has got some great advice for you. He says you can have a rewarding time in ham radio for about $100 of spending.

The post is the advice he wished he had been given in 2015 when he got his license. It turns out you can get on the air very inexpensively these days, especially if you aren’t afraid to build gear from kits.

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Muscle Your Way Into Music

May 28, 2018 by 6 Comments

Inspired by an old Old Spice commercial, [Juliodb96] decided he too wanted to make music by flexing his muscles. An Arduino and a MyoWare sensor did the trick. However, he also tells you how to make your own sensors, if you are so inclined. You can see the instrument in action in the video below.

If you use the ready-made MyoWare sensors, this is a pretty easy project. You just respond to sensor input by playing some notes. If you decide to roll your own, you’ll have some circuit building ahead of you.

In particular, the signal conditioning for the sensors involves filtering to eliminate signals not in the 20 Hz to 300 Hz passband, several amplifiers, a rectifier, and a clipper. This requires 3 IC packages and a handful of discrete components.

Unlike the original commercial (see the second video, below), there are no moving parts for actuating actual instruments. However, that wouldn’t be hard to add with some servo motors, air pumps, and the like. This may seem frivolous, but we had to wonder if it could be used to allow musical expression for people who could not otherwise play an instrument.

This isn’t the first time we’ve seen the MyoWare in action. We’ve even talked about signal processing that is useful for this kind of application.

The Robots Were Coming! The Robots Were Coming!

May 28, 2018 by 43 Comments

The recent influx of home assistants proves that everything old is new again. If we told you about a life-sized robot that was self-charging, had a map of your home for navigation, and responded to voice commands, you’d assume we were going to point you to a Kickstarter or a new product release. Instead, we will point you to this post about a robot marketed in 1985.

You have to put all this in context. In 1985 the personal computer was practically a solution in search of a problem. Back then it was wildly popular to predict that every home would one day have a computer. But we weren’t quite sure what they were going to be doing with it. Home finance, games, and storing recipes were all popular guesses. A few far-sighted folks realized that music, photos, and even video might one day be major selling points. Everyone wanted a piece of this market but no one really understood what the market would look like.

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Their Battery Is Full Of Air

May 26, 2018 by 46 Comments

Storing electrical energy is a huge problem. A lot of gear we use every day use some form of battery and despite a few false starts at fuel cells, that isn’t likely to change any time soon. However, batteries or other forms of storage are important in many alternate energy schemes. Solar cells don’t produce when it is dark. Windmills only produce when the wind blows. So you need a way to store excess energy to use for the periods when you aren’t creating electricity. [Kris De Decker] has an interesting proposal: store energy using compressed air.

Compressed air storage is not a new idea. On a large scale, there have been examples of air compressed in underground caverns and then released to run a turbine at a future date. However, the efficiency of this is poor — around 40 to 50 percent — mainly because the air heats up during compression and often needs to be prewarmed (using energy from another source) prior to decompression to prevent freezing. By comparison, batteries can be 70 to 90 percent efficient, although they have their own problems, too.

The idea explored in this paper is not to try to store a power plant’s worth of energy in a giant underground cavern, but rather use smaller compressed air setups like you would use batteries to store power at the point of consumption. The technology is called micro-CAES (an acronym for compressed air energy storage).

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NASA Remotely Hacks Curiosity’s Rock Drill

May 25, 2018 by 64 Comments

We have a lot of respect for the hackers at NASA’s Jet Propulsion Laboratory (JPL). When their stuff has a problem, it is often millions of miles away and yet they often find a way to fix it anyway. Case in point is the Curiosity Mars rover. Back in 2016, the probe’s rock drill broke. This is critical because one of the main things the rover does is drill into rock samples, collect the powder and subject it to analysis. JPL announced they had devised a way to successfully drill again.

The drill failed after fifteen uses. It uses two stabilizers to steady itself against the target rock. A failed motor prevents the drill bit from retracting and extending between the stabilizers. Of course, sending a repair tech 60 million miles is not in the budget, so they had to find another way. You can see a video about the way they found, below.

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