A friend of mine at work has crafted a tiny HTTP web server in C to run on the Arduino Uno to provide an interface to manipulate external devices (imagine turning on lights, adjusting the thermostat or even opening the garage door).
Wouldn’t it be cool if you could control your MIDI equipped digital piano from your iPhone? Imagine a player piano capable of jukebox queuing up MIDI or Audio files and playing them in order. That was my goal! RPI to the rescue.
Required Ingredients:
Raspberry Pi – Model B, 512MB RAM, 16GB SD Card, Raspbian Linux, Apple 12W USB Power Adapter, USB WiFi Dongle
USB MIDI Digital Device (e.g. Yamaha Clavinova CLP-440 with USB MIDI port and RCA L+R Audio Inputs)
My original thought was to turn the Yamaha speakers into a AirPlay device for our many iOS devices. It’s nice to pipe in background tunes without having to hook up a device. AirPlay is great way to do that but I didn’t want to spend $100+ to be able to do that. The Raspberry Pi is more than capable of doing this. I found an extremely helpful blog post here: http://www.raywenderlich.com/44918/raspberry-pi-airplay-tutorial
NOTE: Power is a big issue for the Raspberry Pi. If you are using a WiFi dongle or any other USB device, I recommend making sure your power supply has enough kick to keep the RPI going. I started out with a microUSB adapter that advertised 700mA but performance became very unstable, especially under load. I switched to a 12W Apple adapter that I had handy and the problems disappeared. The RPI FAQ recommends 1.2A (1200mA).
Dequeue Service: Run the cron.sh script to have the RPI scan for new midi or wave files to play. Run it with:
bash -x cron.sh 0<&- 1>/dev/null 2>/dev/null &
Apache: Install apache http with mod_php and mysql support
Website Code: Install index.php, setup.php and the folder.png files into the document root of your webserver. Upload the MIDI (*.mid) and WAVE (*.wav) files to this location. Be sure to update $globalBase in setup.php to the folder where these files are located.
AirPlay via Raspberry Pi
Adam Burkepile has the best tutorial I’ve found on how to set up a RPI for AirPlay:
The RPI is great for a tiny file server! At the least, having it run an AFP server will allow quick drag and drop transfer from your Macs. A Samba service for Windows shares is easy to set up as well.
sudo apt-get install netatalk
Yes, it is that easy. Finder will now show your Raspberry Pi under “shared” along with any other local network shares:
I wanted to put together a simple two LED flasher circuit that would use the fewest parts and low power. My first project of this type used the NE555 timer IC but besides the chip, it requires more power than what I would like to use. Using a couple low-power NPN transistors, the circuit should be able to run for hours on a 9v battery.
The Circuit
I decided to use two 2N3904 transistors (a low power NPN transistor). This design uses only 10 components but I added additional resistor to inline with the power source. It could be removed and the other resistors adjusted to lower the power.
I assembled the circuit using a low cost breadboard I picked up at Fry’s Electronics. Using a breadboard allowed me to play around with different components, especially the capacitors and resistors to tweak the flash rate and brightness.
Single LED Flasher
The simplest single LED Flasher circuit I have found uses a single transistor (NPN), 2 resistors and 1 capacitor. This circuit uses the transistor as a Negistor using the NDR (negative differential resistance) effect. The transitor will block current until the voltage threshold charging on C1 reach something close to 9v, at which point the voltage will become large enough to get the emitter-base junction to avelanche and drain the current through the LED.
To Engineer is Human: The Role of Failure in Successful Design by Henry Petroski
This is a great book to remind us of the purpose of engineering and the dangers we face when designing technical bridges (and physical ones) across the unknown.
Petroski wrote this in the early 80’s and the examples and illustrations are sometimes dated but still practical. I found the section on computers, “From slide rule to computer” to be particularly interesting. His case still hold true for the faster/newer techno-driven culture of the 21st century.
We have come to be a society that is so quick to change that we have lost the benefits of one of mankind’s greatest tools–experience. – Henry Petroski
Engineering is very dependant upon feedback for improvement. The goal of providing a design solution for the lowest cost will mean that materials, processes and other costly items will be minimized to achieve the most economical/efficient solution. Unfortunately, there are things that we do not know about (the trite, “we don’t know about what we don’t know” phrase comes to mind) that can be or become significant issues in the design. The Tacoma Narrows Bridge is a great example of this.
Engineering attempts to introduce “safety factors” into the design model to cover for the unknowns but this can often be inadequate, as was the case of the walkway collapse at the Kansas City Hyatt Regency Hotel.
Failures, while unfortunate and often deadly, should also be opportunities for improvement. Petroski argues that it is important that details of failures be broadcast to provide corrective feedback to all engineers so that future designs will build on these learnings.
This autobiography of Steve Wozniak is a delightful recount of the birth of the personal computer.
Before cell phones that fit in the palm of your hand and slim laptops that fit snugly into briefcases, computers were like strange, alien vending machines. They had cryptic switches, punch cards and pages of encoded output. But in 1975, a young engineering wizard named Steve Wozniak had an idea: What if you combined computer circuitry with a regular typewriter keyboard and a video screen? The result was the first true personal computer, the Apple I, a widely affordable machine that anyone could understand and figure out how to use.
Wozniak’s life—before and after Apple—is a “home-brew” mix of brilliant discovery and adventure, as an engineer, a concert promoter, a fifth-grade teacher, a philanthropist, and an irrepressible prankster. From the invention of the first personal computer to the rise of Apple as an industry giant, iWoz presents a no-holds-barred, rollicking, firsthand account of the humanist inventor who ignited the computer revolution. 16 pages of illustrations.
This sequel to Richard Feynamn’s Six Easy Pieces grabs six more additional lectures from his famous three-volume series, Lectures on Physics. In this book, Feynman unfolds the complexity of Relativity, Symmetry and Space-Time. As is typical for his style, he makes these very complex subjects approachable, but then drives deeper to reveal the mathematics behind the mysteries. The narrative and related equations are definitely geared toward math and science students.
As is his genius, Richard Feynman often unpacks complex concepts through the use of practical analogies. His description of curved space in Chapter 6 was one of my favorite sections (p. 112).
Curved Space
In order to understand this idea of curved space in two dimensions you really have to appreciate the limited point of view of the character who lives in such a space. Suppose we imagine a bug with no eyes who lives on a plane, as show in Figure 6-1. He can move only on the plane, and he has no way of knowing that there is any way to discover any “outside world.” (He hasn’t got your imagination.) We are, of course, going to argue by analogy. We live in a three-dimensional world, and we don’t have any imagination about going off our three-dimensional world in a new direction; so we have to think the thing out by analogy. It is as though we were bugs living on a plane, and there was a space in another direction. That’s way we will first work with the bug, remembering that he must live on his surface and can’t get out.
As another example of a bug living in two dimensions, let’s imagine one who lives on a sphere. We imagine that he can walk around on the surface of the sphere, as in Figure 6-2, but that he can’t look “up,” or “down,” or “out.”
Now we want to consider still a third kind of creature. He is also a bug like the others, and also lives on a plane, as our first bug did, but this time the plane is peculiar. The temperature is different at different places. Also, the bug and any rules he uses are all made of the same material which expands when it is heated. Whenever he puts a ruler somewhere to measure something the ruler expands immediately to the proper length for the temperature at that place. Whenever he puts any object–himself, a ruler, a triangle, or anything–the thing stretches itself because of the thermal expansion.
Feynman uses this constructed analogy to explain how the bug would get different measurements in each of these “worlds.” The bug is able to determine what type of world it lives in based on the measurements. It is interesting to see through his example that the bug on the sphere experiences the same measurements as the bug on the temperature varying hotplate (both can measure a triangle with an angle-sum of 270 degrees where the bug in the plane would see a maximum sum of 180 degrees). Scientist speculate on the “space” curvature of the universe by conducting experiments. So far, it is inconclusive.
In this book, Feynman also covers a refresher course on Vectors (Ch. 1), discusses the Symmetry in Physical Laws (Ch. 2), does a detailed analysis of The Special Theory of Relativity (Ch. 3), Relativistic Energy and Momentum (Ch. 4), Space-Time (Ch. 5), and Curved Space (Ch. 6).
Realativity
The Special Theory of Realativity (p. 49) is a facinating approach to motion that for over 200 years was ruled by equations developed by Isaac Newton. In Newton’s Second Law,
which is the same as F=ma (where a is acceleration or the time derivative of velocity, dv/dt), the assumption is that mass (m) is a constant. Einstein corrected this formula with his theory by saying that mass has the changing value,
where mo is the “rest mass” of a body when it is not moving and c is the speed of light (186,000 mi/s or 3×10^5 km/s).
Dr. João Magueijo presents a theory that allows for variable speed of light (VSL). This is a rather controversial subject as it deals with a value in physics that has traditionally been constant (c, the value of the speed of light, 186,000 mps or 300,000 kps). The speed of light is the underpinnings of Einstein’s theories of special relativity, as seen in the famous E=mc² equation.
The Book
While dealing very little with the science of theory itself, João does provide a very entertaining look at the often painful, slow and bureaucratic scientific process. He spends considerable time presenting the histories and struggles of scientist like Einstein as well as his colleagues. These narrative backdrops are used to provide contrast and similarities to his own scientific speculation. These also provide the basis for the bipolar challanges against and support for VSL.
The Theory
João proposes that the speed of light is dependant upon energy or space-time. He postulates that during the moment of creation, the high energy big bang of those intial moments could well increase the speed at which light travels by sixty orders of magnitude (that is 1 with 60 zeros). This could explain the horizon problem of cosmology and propose an alternative to cosmic inflation. This would reveal itself near black holes or cosmic strings.
The Scientist
Dr. João Magueijo received his doctorate from Cambridge, has been a faculty member at Princeton and Cambridge, and is currently a professor at Imperial College, London. A lecture from João can be found here: http://forum.wgbh.org/wgbh/forum.php?lecture_id=3195
Joãowrites, “we do not notice energy, but only variations in energy.” He concludes the book by saying, “It’s difficult to sum up where VSL stands, as I finish this book… VSL is now an umbrella for many different theories.”
The LEGO mindstorm robotics kit is a popular programmable controller that can allow kids and adults alike to enter the world of robotics. I am currently playing with a few free software programs that my friend found that let you simulate virtual robots, including the mindstorm.
Richard Feynman is Nobel prize winning physicist and famous communicator. I put together a collection of YouTube Feynman videos:
Transcript:
I have approximate answers and possible beliefs about different things, but I’m not too sure of anything. The many things I don’t know anything about, such as whether it means anything to ask why we’re here and what the question might mean, I might think about a little, but if I can’t figure it out, I go into something out. I don’t have to know an answer, and I don’t feel frightened by not knowing things. Being lost in the mysterious universe without having any purpose is the way it really is, as far as I can tell. Possibly, it doesn’t frighten.
I have a friend who’s an artist, and sometimes taking a view which I don’t agree with very well. He holds up a flower and says, “Look how beautiful it is,” and I’ll agree, but he says, “You see as I, as an artist, can see how beautiful this is, but you, as a scientist, take it all apart and it becomes a dull thing.” I think that he’s kind of nutty first of all. The beauty that he sees is available to other people and to me too, although I may not be as refined as he is. I can’t appreciate the beauty of the flower at the same time as I see much more about the flower than he sees. I can imagine the souls in there, the complicated actions inside, which also have a beauty. It’s not just beauty at this dimension of one centimeter; there’s also beauty at a smaller dimension. The inner structure, the processes, the fact that the colors and the flower are evolved in order to attract insects to pollinate it is interesting. It means the insects can see the color, which adds a question: is this aesthetic sense also exist in the lower forms? Why is it aesthetic? All kinds of interesting questions which science knowledge only adds to the excitement and mystery in the aura of a flower. It only adds to the excitement and mystery, but I don’t understand how it subtracts.
I have always been fascinated with the study of Artificial Intelligence. I began my interest as many computer science majors by simulating intelligence through maze solving LISP automated mice. These are brute force methods that appear to be intelligent by recursively exploring every possible solution. This is not intelligence. It is merely programmatic problem solving.
What is Artificial Intelligence? How do we copy the creation that is the human mind and intellect, and impress that upon silicon and wires? Is it even possible?
Beyond AI: Creating the Conscience of the Machine by J. Storrs Hall
Artificial intelligence (AI) is now advancing at such a rapid clip that it has the potential to transform our world in ways both exciting and disturbing. Computers have already been designed that are capable of driving cars, playing soccer, and finding and organizing information on the Web in ways that no human could. With each new gain in processing power, will scientists soon be able to create supercomputers that can read a newspaper with understanding, or write a news story, or create novels, or even formulate laws? And if machine intelligence advances beyond human intelligence, will we need to start talking about a computer’s intentions?
This book contemplates several interesting topics related to artificial intelligence, including the consequences of actually creating a systems that is intelligent. A lot of what is intelligence appears to be search and pattern matching. It seems that we build complex associations that help us grapple with our environment and interact with others in an intelligent fashion.
What is intelligence? I believe that we will continue to see progress in developing artificial minds. Predictive expert systems already provide a sense of “smarts” but they are not creating anything new. Attempts to build systems that take inputs, learn and even postulate solutions (as in mathematical proofs) have been limited in their success. It seems that these intelligent systems hit a “glass ceiling” beyond which they are unable to produce anything new.
Tools, Programs and Links
SHRDLU is a program for understanding natural language, written by Terry Winograd at the M.I.T. Artificial Intelligence Laboratory in 1968-70. – http://hci.stanford.edu/~winograd/shrdlu/
Before cell phones that fit in the palm of your hand and slim laptops that fit snugly into briefcases, computers were like strange, alien vending machines. They had cryptic switches, punch cards and pages of encoded output. But in 1975, a young engineering wizard named Steve Wozniak had an idea: What if you combined computer circuitry with a regular typewriter keyboard and a video screen? The result was the first true personal computer, the Apple I, a widely affordable machine that anyone could understand and figure out how to use.
