According to this report at FOX News Technology, the FAA may use “deadly force” against your remote-controlled quadcopter, ahem, “drone” if you’re flying within a 36-mile radius of the Super Bowl this weekend. We call shenanigans on using “deadly” for things that aren’t alive to begin with, but we have no doubt that they intend to take your toys away if you break the rules. We are curious to see how they’re going to do it, though.
The actual Notice to Airmen (NOTAM) has the details, and seems pretty comprehensive. You can’t fly your sea plane or go crop dusting either. Model rocketry is off the table within the circle on Sunday afternoon. It tickles our superiority-bone to note that only “drones” made the headlines.
But we also see our loophole! The ban only extends from the ground’s surface up to 18,000 ft (5,500 m) above sea level. (No, we’re not thinking of flying quadcopters in tunnels under the stadium.) They didn’t rule out high-altitude balloon flight over the Super Bowl? Don’t even think about it.
My DSL line downloads at 6 megabits per second. I just ran the test. This is over a pair of copper twisted wires, the same Plain Old Telephone Service (POTS) twisted pair that connected your Grandmother’s phone to the rest of the world. In fact, if you had that phone you could connect and use it today.
I can remember the old 110 bps acoustic coupler modems. Maybe some of you can also. Do you remember upgrading to 300 bps? Wow! Triple the speed. Gradually the speed increased through 1200 to 2400, and then finally, 56.6k. All over the same of wires. Now we feel short changed if were not getting multiple megabits from DSL over that same POTS line. How can we get such speeds over a system that still allows your grandmother’s phone to be connected and dialed? How did the engineers know these increased speeds were possible?
The answer lies back in 1948 with Dr. Claude Shannon who wrote a seminal paper, “A Mathematical Theory of Communication”. In that paper he laid the groundwork for Information Theory. Shannon also is recognized for applying Boolean algebra, developed by George Boole, to electrical circuits. Shannon recognized that switches, at that time, and today’s logic circuits followed the rules of Boolean Algebra. This was his Master’s Thesis written in 1937.
Shannon’s Theory of Communications explains how much information you can send through a communications channel at a specified error rate. In summary, the theory says:
There is a maximum channel capacity, C,
If the rate of transmission, R, is less than C, information can be transferred at a selected small error probability using smart coding techniques,
The coding techniques require intelligent encoding techniques with longer blocks of signal data.
What the theory doesn’t provide is information on the smart coding techniques. The theory says you can do it, but not how.
In this article I’m going to describe this work without getting into the mathematics of the derivations. In another article I’ll discuss some of the smart coding techniques used to approach channel capacity. If you can understand the mathematics, here is the first part of the paper as published in the Bell System Technical Journal in July 1948 and the remainder published later that year. To walk though the system used to fit so much information on a twisted copper pair, keep reading.
What’s the smallest RGB LED cube? A 1x1x1 cube is easy, but it’s a stupid joke and we’ve heard it before. No, to build the smallest LED cube, you’ll have to stuff 64 RGB LEDs into a cubic inch, like [Hari] did with his miniscule LED cube.
One might think that individually addressable RGB LEDs are the way to go with an LED cube this small. Anything else would hide the LEDs behind a mess of wires. This isn’t the case with [Hari]’s LED cube – he’s using standard surface mount RGB LEDs for this build. But how is he connecting the things?
The entire build was inspired by the a much earlier project, the Charliecube. This LED cube, like [Hari]’s uses Charlieplexing to condense all the connections for a column of LEDs to only four wires. Repeat that sixteen times, and [Hari] built himself a tiny, one-inch cube of glowey goodness.
The cube itself was built with a PCB backplane designed in Eagle and fabbed at OSHPark. The LEDs are driven by an Arduino Nano. If you’d like to build your own, or you’re a masochist for dead bug soldering, you can grab all the design files over on [Hari]’s hackaday.io project page.
Kids these days, they have it so easy. Back in the old days, we learned our elements the hard way, by listening to “The Elements” by Tom Lehrer over and over until the vinyl wore out on the LP. Now, thanks to [Karyn], kids can learn the elements by playing “Battleship” – no tongue-twisting lyrics required.
For anyone familiar with the classic “Battleship” game, you’ll wonder why no one thought of this before. [Karyn]’s version of the game is decidedly low-tech, but gets the job done. She printed out four copies of the periodic table, added letters to label the rows, and laminated them. A pair of tables goes into a manila file folder, the tops get clipped together, and dry-erase markers are used to mark out blocks of two to five elements to represent the ships of the Elemental Navy on the lower table. Guesses at the location of the enemy ships can be made by row and series labels for the elementally challenged, or better yet by element name. Hits and misses are marked with Xs and Os on the upper table, and play proceeds until that carrier hiding in the Actinide Archipelago is finally destroyed.
This is pure genius in its simplicity and practicality, but of course there’s room for improvement. The action-packed video after the break reveals some structural problems with the file folders, so that’s an obvious version 2.0 upgrade. And you can easily see how this could be used for other tabular material – Multiplication Table Battleship? Sounds good to us. And if your nippers catch the chemistry bug from this, be sure to take a deeper dive into the structure of the periodic table with them.
Now, if you’ll excuse me: “There’s antimony, arsenic, aluminum, selenium, and hydrogen and oxygen and nitrogen and rhenium….”
Brushless motors are everywhere now. From RC planes to CNC machines, if you need a lot of power to spin something really fast, you’re probably going to use a brushless motor. A brushless motor requires a motor controller, and for most of us, this means cheap Electronic Speed Controllers (ESC) from a warehouse in China. [Ben] had a better idea: build his own ESC. He’s been working on this project for a while, and he’s polishing the design to implement a very cool feature – position control.
We’ve seen [Ben]’s work on his custom, homebrew ESC before. It is, by any measure, a work of art. It’s capable of driving brushless and brushed motors with a powerful STM32F4 microcontroller running ChibiOS that’s able to communicate with other microcontrollers through I2C, UART, and CAN bus. If you want to build anything with a motor – from a CNC machine to an RC helicopter to an electric long board – this is the motor controller for you.
[Ben]’s latest update considers position encoders. Knowing how fast a motor is turning is very important to knowing how fast a wheel is turning, how much torque the motor is generating, and an awesome step in building the finest motor controller ever made.
Like the last update, [Ben] demonstrates the great control program written for this ESC. This GUI programs the microcontroller on the controller, with protection from high and low voltages and currents, high RPMs, duty cycle changes, and support for regenerative braking.
While laser cutting remains the dominant force for rapid prototyping anything made of plastic, MDF or wood, the real holy grail is the ability to cut metal — something most laser cutters are just not capable of.
In the industry, this is done using extremely high-powered laser cutters, plasma cutters, or water jet cutters. All of which are very pricey equipment for a hacker. Until now anyway. Introducing the Tinijet, the missing tool for affordable water jet cutting.
We first covered this project a few years ago when it was just a university research project called Hydro — it’s since evolved immensely, and will be available for sale very soon.
[Ian Jimmerson] has constructed a detailed model of a radial engine out of wood and MDF for an undisclosed reason. Rather than just delivering the wooden engine to wherever wood engines go, [Ian] decided to take the time to film himself disassembling and reassembling his engine, explaining in detail how it works as he goes. He starts by teaching about the cylinder numbering and the different possible cylinder configurations. It only gets better after that, and it’s worth watching the full 20 minutes of video. You’ll leave with a definite understanding of how radial engines work, and maybe build something neat with the knowledge.
Our only complaint is the lack of build photos or construction techniques. It’s a real feat to build something with this many moving parts that can run off an electric drill. Was a CNC involved, or was he one of those hardcore guys who manage to get precision parts with manual methods? Part 1 and 2 after the break.