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17. Test Equipment

J. M. Hughes O'Reilly Media ePub

This chapter is a quick tour of what is available in the way of inexpensive test equipment, starting with the ubiquitous digital multimeter (DMM) and moving on to oscilloscopes, signal generators, and logic analyzers. The focus here is on low-cost tools that will help get the job done without costing a small fortune. In the world of test equipment, it’s all too easy to spend a lot of money, with some types of equipment running upward of $30,000 each (or more). For the vast majority of situations you are likely to encounter when working with common electronics components and devices, that sort of precision and processing speed isn’t necessary.

Now would probably be a good time to talk a bit about things like speed, accuracy, and bandwidth. We’ll cover these topics in more detail later on in relation to each type of instrument, but the main point is that, for the vast majority of things you might want to build or modify, you don’t need an oscilloscope with a bandwdith capable of displaying a 1 GHz signal, nor do you need a digital meter with 4 1/2 digits of resolution. You don’t need an RF spectrum analyzer, or a high-precision pulse generator, or even a frequency counter. When you are working with things that interact with the real world in some fashion, the times involved are typically anywhere from 10 to 1,000 ms (0.01 to 1 second). Physical things usually don’t move much faster than that. If you are working with a microcontroller, it will be running at a much faster rate, but you don’t have visibility into the chip itself, just the inputs and outputs, and they are slow by comparison to the microcontroller’s internal clock.

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Mark Frauenfelder Maker Media, Inc ePub


Safe and easy to use, but a closed system holds back its potential.


Price as tested $1,299

Print volume 5½″×5½″×5½″

Heated bed? No

Print materials PLA, ABS

OS supported Mac, Windows

Print untethered? Yes, over wi-fi or via USB flash drive

Open-source hardware? No

Open-source software? No

Printer control software Cube software

Slicing software Cube software

Last year we reviewed 3D Systems’ entry into the desktop 3D printer market, the Cube. It was a relatively affordable, compact, simple-to-use printer that used closed-source software and proprietary filament cartridges. These elements made this printer less appealing to 3D printing veterans, but great for young or inexperienced makers who want to venture into the world of 3D printing.

This year 3D Systems released the Cube 2, adding a few modifications that make it even safer, quieter, and more kid-friendly, in hopes of better meeting the needs of the education market. Unfortunately the price paid for these changes is reduced print quality.

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D. Suggested Reading

Joan Stigliani O'Reilly Media ePub

[biblio0_001] Ergonomics in Computerized Offices Etienne Grandjean, Taylor & Francis, London, 1987.

[biblio0_002] Promoting Health and Productivity in the Computerized Office Steven Sauter, Marvin Dainoff, and Michael Smith, editors, Taylor & Francis, London, 1990.

[biblio0_003] VDT News Louis Slesin, editor. Bimonthly publication on computer health and safety. P.O. Box 1799, Grand Central Station, New York, NY 10163.

[biblio0_004] Ergonomics, Work, and Health Stephen Pheasant, Aspen Publishing, Inc., Gaithersberg, MD, 1991.

[biblio0_005] Computer Ethics Tom Forester and Perry Morrison, The MIT Press, Cambridge, MA, 1990, 2nd edition 1994.

[biblio0_006] The Electronic Sweatshop Barbara Garson, Penguin Books, New York 1988 (reprint), Simon & Schuster, Inc., 1989.

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11. Camera Models and Calibration

Gary Bradski O'Reilly Media ePub

Vision begins with the detection of light from the world. That light begins as rays emanating from some source (e.g., a light bulb or the sun), which then travels through space until striking some object. When that light strikes the object, much of the light is absorbed, and what is not absorbed we perceive as the color of the light. Reflected light that makes its way to our eye (or our camera) is collected on our retina (or our imager). The geometry of this arrangementparticularly of the ray's travel from the object, through the lens in our eye or camera, and to the retina or imageris of particular importance to practical computer vision.

A simple but useful model of how this happens is the pinhole camera model. [164] A pinhole is an imaginary wall with a tiny hole in the center that blocks all rays except those passing through the tiny aperture in the center. In this chapter, we will start with a pinhole camera model to get a handle on the basic geometry of projecting rays. Unfortunately, a real pinhole is not a very good way to make images because it does not gather enough light for rapid exposure. This is why our eyes and cameras use lenses to gather more light than what would be available at a single point. The downside, however, is that gathering more light with a lens not only forces us to move beyond the simple geometry of the pinhole model but also introduces distortions from the lens itself.

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John Graham-Cumming O'Reilly Media ePub



14 India Street, Edinburgh, Scotland

55 57 19.17 N, 3 12 19.78 W

James Clerk Maxwell

Scotland has produced a great number of famous scientists and inventors, including Alexander Graham Bell (Chapter 4), Lord Kelvin (Chapter 73), John Napier (Chapter 57), John Logie Baird (page 452), and James Watt (page 299). But in the world of mathematics and physics, one name stands above them all: James Clerk Maxwell.

Einstein described Maxwells contributions as the most profound and the most fruitful that physics has experienced since the time of Newton because in 1864 Maxwell showed, in the paper A Dynamical Theory of the Electromagnetic Field , that light is actually formed from electromagnetic waves. He also suggested that there might be other types of radiation obeying the same laws, and it wasnt long before other types of radiation were discovered: radio waves were found by Hertz in 1886, X-rays by Rntgen in 1895, and gamma rays by Villard in 1900.

And, above all, Maxwells important theoretical step underpins Einsteins 1905 work on relativity. But completely changing physics wasnt enough for Maxwells prodigious talenthe also made a major contribution to thermodynamics and the kinetic theory of gases.

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