Kids And Hacking: The One Hour Egg Drop

October 23, 2015 by Al Williams 24 Comments

In the last Hacking and Kids post, I talked about an activity you can do with kids when you don’t have a lot of time or resources. The key idea was to have fun and learn a little bit about open and closed loop control. One of the things I usually briefly mention when I do that is the idea of a design trade: Why, for example, a robot might use wheels instead of legs, or treads instead of wheels.

Engineers and makers perform trades like this all the time. Suppose you are building a data logging system. You want precise samples, large storage capacity, and many channels. But you also want a low cost and low power drain. You might also want high reliability. All of these requirements will lead to different trades. A hard drive would provide a lot of space, but is more expensive, less reliable, larger, and more power hungry than, say, an SD card. So there isn’t a right choice. It depends on which of the factors are most important for this particular design. A data logger in a well-powered rack might be well served to have a terrabyte hard drive, while a battery powered logger in a matchbox that will be up on the side of a mountain might be better off with an SD card.

We can all relate to that example, but it is pretty boring to a kid. You probably can’t get them to design a data logger, anyway. But if I have about an hour and a little prep time, I have a different way to get the same point across. It is a modified version of the classic “egg drop”, but it is simple enough to do in an hour with very little preparation time.

Continue reading “Kids And Hacking: The One Hour Egg Drop” →

An Improvement To Floating Point Numbers

October 22, 2015 by Brian Benchoff 168 Comments

On February 25, 1991, during the eve of the of an Iraqi invasion of Saudi Arabia, a Scud missile fired from Iraqi positions hit a US Army barracks in Dhahran, Saudi Arabia. A defense was available – Patriot missiles had intercepted Iraqi Scuds earlier in the year, but not on this day.

The computer controlling the Patriot missile in Dhahran had been operating for over 100 hours when it was launched. The internal clock of this computer was multiplied by 1/10th, and then shoved into a 24-bit register. The binary representation of 1/10th is non-terminating, and after chopping this down to 24 bits, a small error was introduced. This error increased slightly every second, and after 100 hours, the system clock of the Patriot missile system was 0.34 seconds off.

A Scud missile travels at about 1,600 meters per second. In one third of a second, it travels half a kilometer, and well outside the “range gate” that the Patriot tracked. On February 25, 1991, a Patriot missile would fail to intercept a Scud launched at a US Army barracks, killing 28 and wounding 100 others. It was the first time a floating point error had killed a person, and it certainly won’t be the last.

Continue reading “An Improvement To Floating Point Numbers” →

Nomograms: Complex Analog Calculators Simple For Everyone

October 21, 2015 by Kristina Panos 29 Comments

In the late 1800s, a railway engineer named Philbert Maurice d’Ocagne was part of a group of men faced with the task of expanding the French rail system. Before a single rail could be laid, the intended path had to be laid out and the terrain made level. This type of engineering involves a lot of cut and fill calculations, which determine where dirt must be added or removed. The goal of earthwork is to create a gentle grade and to minimize the work needed to create embankments.

In the course of the project, d’Ocagne came up with an elegant, reusable solution to quickly solve these critical calculations. Most impressively, he did it with little more than a pen, some paper, and a straightedge. By developing and using a method which he called nomography, d’Ocagne was able to perform all the necessary calculations that made the gentle curves and slopes of the French railway possible.

Continue reading “Nomograms: Complex Analog Calculators Simple For Everyone” →

Ultrasonic Power Transfer: UBeam’s Curious Engineering

October 20, 2015 by Brian Benchoff 96 Comments

The future is wireless power, or so say a thousand press releases in my spam folder, and with very few exceptions every single system of wireless power delivery has fallen flat on its face. Except for a few niche cases – RFID tags, Wacom tablets and the S Pen, and the Qi inductive power mats for cell phones – the future of wireless power hardly looks bright, and in some cases seems downright dangerous. No one seems to grasp that wireless power transfer is much more inefficient than using a wire, and the inverse square law only makes everything worse.

Now there’s a new wireless power technology that’s a strange mix of running in stealth mode and sending press releases to every tech outlet on the planet. It’s called uBeam. This company says it will deliver wireless power to the world, but it’s not doing it with giant Tesla-inspired towers of power, radios beamed directly at devices, induction, magnetic resonance, or even light. uBeam transmits power via sound, specifically high intensity ultrasound. uBeam has never demonstrated a prototype, has never released any technical specs, and even some high-profile investors that include [Mark Cuban] have not seen the uBeam working. Despite running in a ‘stealth mode’, it has garnered a lot of press, and has been featured on TechCrunch dozens of times. This may just be a consequence of CrunchFunds’s investment in uBeam, but there’s still more Google News results for a technology that hasn’t even been demonstrated than a reasonable person would expect.

In what is perhaps the greatest breakdown ever posted on the EEVForums, [georgesmith] goes over what uBeam is, how the technology doesn’t make sense, and how far you can take a business before engineers start to say, ‘put up or shut up.’ [georgesmith]’s research goes over just some of what makes uBeam impractical, but digging even further reveals how insane uBeam actually is.

Continue reading “Ultrasonic Power Transfer: UBeam’s Curious Engineering” →

DIY Computer — 1968 Style

October 19, 2015 by Al Williams 39 Comments

What does it mean to “build your own computer?” Today, it is likely to mean you bought a motherboard, a power supply, and a case and put it all together. You might even have made an embedded computer using a few chips, including an off the shelf CPU. However, there are those guys (like me) who have built entire computers using FPGAs and some (not like me) who have built computers out of TTL chips, discrete components, and even relays and we have covered quite a few of them.

It hasn’t always been that easy. Components are readily available now and relatively cheap (especially considering inflation). In the 1960’s, simple components cost more than you pay for them today and back then your hypothetical self was making less money. In just about every way imaginable, the cost was prohibitive.

So what did you do if you were a kid saving money from a paper route in 1968 and you wanted to build a computer? Maybe you turned to How to Build a Working Digital Computer a book published in 1968 by [Edward Alcosser], [James Phillips], and [Allen Wolk]. This book did as the title promised: you could build a working digital computer. The components, though, were paper clips, tin cans, thread spools, and other household items. The only real electronic components you had to use were light bulbs and a battery, although you might also use store-bought switches in some places instead of the homemade versions shown in the book.

Continue reading “DIY Computer — 1968 Style” →

Breaking: Drone Registration Will Be Required Says US DoT

October 19, 2015 by Brian Benchoff 77 Comments

Today, the US Department of Transportation announced that unmanned aerial systems (UAS) will require registration in the future.

The announcement is not that UAS, quadcopters, or drones would be required to be registered immediately. This announcement is merely that a task force of representatives from the UAS industry, drone manufacturers, and manned aviation industries would provide recommendations to the Department of Transportation for what types of aircraft would require registration. The task force is expected to develop these recommendations and deliver a report by November 20.

A Short History of FAA Model Aircraft Regulation

Introduced in 1981, AC 91-57 was the model aircraft operating standards for more than 30 years. This standard suggested that model pilots not fly higher than 400 feet, and to notify a flight service station or control tower when flying within three miles of an airport.

The FAA Modernization And Reform Act Of 2012 (PDF) required the FAA to create a set of rules for unmanned aerial systems, however the FAA is expressly forbidden from, ‘promulgating any rule or regulation regarding model aircraft.’ The key term being, ‘model aircraft’. This term was defined by the FAA as being, “an unmanned aircraft that is capable of sustained flight in the atmosphere; flown within visual line of sight of the person operating the aircraft; and flown for hobby or recreational purposes.” Anything outside of this definition was an unmanned aerial system, and subject to FAA regulations.

While this definition of model aircraft would have been fine for the 1980s, technology has advanced since then. FPV flying, or putting a camera and video transmitter on a quadcopter, is an extraordinarily popular hobby now, and because it is not ‘line of sight’, it is outside the definition of ‘model aircraft’.

This interpretation has not seen a great deal of countenance from the model aircraft community; FPV flying is seen as a legitimate hobby and even a sport. The entire domain of model aircraft aviation is expanding, and the hobby has never been as popular as it is now.

The Safety of Model Aviation

The issue of drone regulation focuses nearly entirely on the safety of airways in the United States; model aviators flying within five miles of an airport must ask the airport or control tower for permission to fly. To that end, the FAA created the B4UFLY app that takes the trouble out of reading sectional charts and checking up on the latest NOTAMs and TFRs.

However, the FAA is increasingly concerned with drones, multicopters, and model aircraft. In a report issued last summer, the FAA cited a marked increase in the number of ‘close calls’ between manned aircraft and model aircraft. The Academy of Model Aeronautics went over this data and found a different story: only 3.5% of sightings were ‘close calls’ or ‘near misses’. The FAA data is questionable – the reports cited include a drone flying at 51,000 feet over Washington DC. Not only is this higher than any civilian passenger aircraft capable of flying, the ability for any civilian remote-controlled aircraft to operate at this altitude is questionable at best.

Nevertheless, the requirement for registration has been greatly influenced by the perceived concerns of regulators for mid-air collisions.

What exactly will require registration?

The group of industry representatives responsible for delivering the recommendations to the Department of Transportation will take into account what aircraft should be exempt from registration due to a low safety risk. Most likely, small toy quadcopters will be exempt from registration; it’s difficult to fly a small Cheerson quadcopter outside anyway. Whether this will affect larger quadcopters and drones such as the DJI Phantom, or 250 class FPV racing quadcopters remains to be seen.

TEMPEST: A Tin Foil Hat For Your Electronics And Their Secrets

October 19, 2015 by Elliot Williams 38 Comments

Electronics leak waves and if you know what you’re doing you can steal people’s data using this phenomenon. How thick is your tinfoil hat? And you sure it’s thick enough? Well, it turns out that there’s a (secret) government standard for all of this: TEMPEST. Yes, all-caps. No, it’s not an acronym. It’s a secret codename, and codenames are more fun WHEN SHOUTED OUT LOUD!

The TEMPEST idea in a nutshell is that electronic devices leak electromagnetic waves when they do things like switch bits from ones to zeros or move electron beams around to make images on CRT screens. If an adversary can remotely listen in to these unintentional broadcasts, they can potentially figure out what’s going on inside your computer. Read on and find out about the history of TEMPEST, modern research, and finally how you can try it out yourself at home!

Continue reading “TEMPEST: A Tin Foil Hat For Your Electronics And Their Secrets” →