Posts about how things work

How a Differential Gear Works

Very nice webcast (of an old 1930’s filmstrip by GM) explaining how a differential gear works.

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Build Your Own Tabletop Interactive Multi-touch Computer

This is a fantastic Do-It_Yourself (DIY) engineering story. Very interesting, definitely go read the whole article: Build Your Own Multitouch Surface Computer

First, some acknowledgments are in order. Virtually all the techniques used to create this table were discovered at the Natural User Interface Group website, which serves as a sort of repository for information in the multitouch hobbyist community.

In order for our setup to work, we needed a camera that senses infrared light, but not visible light. It sounds expensive, but you’d be surprised. In this section, we’ll show you how we created an IR camera with excellent resolution and frame-rate for only $35—the price of one PlayStation 3 Eye camera. “But that’s not an IR camera,” you say? We’ll show you how to fix that.

As it turns out, most cameras are able to sense infrared light. If you want to see first-hand proof that this is the case, try this simple experiment: First, find a cheap digital camera. Most cell phone cameras are perfect for this. Next, point it at the front of your TV’s remote control. Then, while watching the camera’s display, press the buttons on the remote. You’ll see a bluish-white light that is invisible to the naked eye. That’s the infrared light used by the remote to control the TV.

Like the computer, the projector we used for the build was something we scavenged up. The major concern for a projector to use in this kind of system is throw distance—the ratio between projection distance and image size. Short-throw projectors, which are sold by all the major projector brands, work the best for this kind of project, because they can be set up at the bottom of the cabinet and aimed directly at the surface. Unfortunately, they also tend to be more expensive.

Ever thrifty, we went with a projector we could use for free: an older home-theater projector borrowed from a friend. Because of the longer throw distance on this model, we had to mount the projector near the top of the cabinet, facing down, and use a mirror to reflect the image up onto the screen. For this we ordered a front-side mirror (a mirror with the reflective surface on the front of the glass, rather than behind it) to eliminate any potential “ghosting” problems, caused by dual reflections from the front and back of the glass in an ordinary mirror.

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So What are Genetic Algorithms?

Genetic Algorithms: Cool Name and Damn Simple is a very nice explanation with python code of genetic algorithms.

What Can Genetic Algorithms Do?
In a word, genetic algorithms optimize. They can find better answers to a question, but not solve new questions. Given the definition of a car, they might create a better car, but they’ll never give you an airplane.

For each generation we’ll take a portion of the best performing individuals as judged by our fitness function. These high-performers will be the parents of the next generation.

We’ll also randomly select some lesser performing individuals to be parents, because we want to promote genetic diversity. Abandoning the metaphor, one of the dangers of optimization algorithms is getting stuck at a local maximum and consequently being unable to find the real maximum. By including some individuals who are not performing as well, we decrease our likelihood of getting stuck.

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How Marbles Are Made

More posts on how things work: Why do We Sleep?Why is it Colder at Higher Elevations?What Are Flowers For?

How Antibiotics Kill Bacteria

How Antibiotics Kill Bacteria

Since the first antibiotics reached the pharmacy in the 1940s, researchers discovered that they target various pieces of machinery in bacterial cells, disrupting the bacteria’s ability to build new proteins, DNA, or cell wall. But these effects alone do not cause death, and a complete explanation of what actually kills bacteria after they are exposed to antibiotics has eluded scientists.

The group found that all bactericidal antibiotics, regardless of their initial targets inside bacteria, caused E. coli to produce unstable chemicals called hydroxyl radicals. These compounds react with proteins, DNA, and lipids inside cells, causing widespread damage and rapid death for the bacteria.

With the results of these two experiments, the researchers were able to identify three major processes implicated in gentamicin-induced cell death: protein transport, a stress response triggered by abnormal proteins in the cell membrane, and a metabolic stress response.

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Compounding is the Most Powerful Force in the Universe

A talking head with some valuable info. I remember my father (a statistics professor) getting me to understand this as a small child (about 6 years old). The concept of growth and mathematical compounding is an important idea to understand as you think and learn about the world. It also is helpful so you understand that statistics don’t lie but ignorant people can draw false conclusions from limited data.

It is unclear if Einstein really said this but he is often quoted as saying “compounding is the most powerful force in the universe.” Whether he did or not, understanding this simple concept is a critical component of numeracy (literacy with numbers). Also quoted at times as: “Compound interest is the eighth wonder of the world.” My guess is that people just find the concept of compounding amazing and then attribute quotes about it to Einstein.

I strongly encourage you to watch at least the first 2 segments (a total of 15 minutes). And then take some time and think. Take some time to think about compounding in ways to help you internalize the concepts. You can also read his book: The Essential Exponential For the Future of Our Planet by Albert Bartlett.

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Home Repairs

In making a repair to my toilet last week I found this useful resource: Replace The Toilet Fill Valve, Flush Valve Or Flapper

Your first step is to shut off the water. In most cases, you’ll have a shutoff valve right next to the toilet coming either through the floor or out of the wall… If the height of your valve is adjustable, set the height before you install the valve (Photo 5). If your valve is a different style from the one we show, check the directions. After mounting the valve (Photo 6), connect the fill tube (Photo 7). The fill tube squirts water into the overflow tube to refill the toilet bowl. The water that refills the tank gushes from the bottom of the fill valve. When you install the valve and supply lines, turn the nuts finger-tight. Then give each another one-half turn with a pliers. When you turn the water supply back on, immediately check for leaks and tighten the nuts a bit more if necessary.

The site does a great job of explaining what needs to be done and provides excellent graphics. It is also interesting to take a look at how things we use actually work.

Clean Clothes Without Soap

photo of eco washing balls

The Soap-free Green Laundry Revolution by Tania Rabesandratana:

Then, there’s the sheer weirdness of entirely eradicating washing powders in favor of such an intangible washing concept. “The balls are made of a special kind of plastic,” explains Steve Jones, the founder of Ecotopia, which sells a variety of washing balls he believes are top of their league, and a scientific breakthrough. “It is the chemical reaction between the plastic and the agitated water that actually does the washing,” he says. The product’s blurb says the balls “produce ionized oxygen that activates the water molecules naturally and allows them to penetrate deep into clothing fibers to lift dirt away.”

Right. Let’s go back to washing basics. Our machine works by combining three actions. First comes chemical action. Here, detergents act as surfactants: they lower the water’s surface tension, making it more likely to mix with oil, so that yucky grease and grime can be removed during rinsing. Second comes the mechanical action from the spinning of the washing machine drum. And finally, there is heat action, which consists of dunking your laundry in hot water.

The eco balls mostly increase the mechanical action so that you can do without the chemical action, thereby saving money and avoiding the use of evil pollutants. The increase of mechanical action also does away with the need for heat action, which in turn conserves electricity and water, which is good for your wallet and your planet.

Pretty cool, if they actually work. I think I might have to try these out. For the next stage of the process, DryerMax Dryer Balls claim to cut the drying time by 25% and soften the fabric. Some other cool gadgets and gizmos.

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