– “Teardowns: Learn How Electronics Work by Taking Them Apart,” by Bryan Bergeron; $25. The title strikes right to the point here, and the author tells you how things work, from smoke alarms to electric guitars, and provides pictures of the insides. Once you know how something works, you can think about ways to improve it or even make it obsolete.

– “Teach Yourself Electricity and Electronics,” by Stan Gibilisco; $35. This is like a text book, with a quiz at the end of each chapter. It’s well done, and includes some useful algebraic formulas. Basic stuff you should know.

– “Robot Builder’s Bonanza, fourth edition.” By Gordon McComb; $30. Build your own electronic sensors, make a spider robot out of electric guitar strings.

– “Arduino, a Quick Start Guide,” by Mark Schmidt; $35 and “Programming and Customizing the PICAXE Microcontroller,” by David Lincoln; $50. Both these books teach the reader how to program the two most popular circuit boards for controlling electro-mechanical devices.

– “15 Dangerously Mad Projects for the Evil Genius,” by Simon Monk; $25. The latest in the long-running Evil Genius series. What intrigued us here was how to make a magnetic coil gun. Projectile velocity is dismal; work on it.

– “Make, #27,” a regular magazine published by O’Reilly Books, $15 per issue. Covers many subjects but this one features turning a Roomba carpet cleaner into a roving spy robot.

Last but far from least each issue of the monthly magazines Popular Science and Popular Mechanics have instructions for building electro-mechanical projects. These are not toys! Want to build your own electron microscope?

A couple guys from Crucial stopped by and we talked over memories. This wasn’t memories about us — we never saw them before — but the memories in computers.

Crucial is one of the two leading vendors of memory chips; the other is Kingston. What lots of memory does for your computer is make it run faster and cleaner. We have said this before, but it’s definitely worth saying again: Adding memory is the cheapest thing you can do to improve your computer’s performance.

But how do you know what memory chips to add? Are there are a lot of possibilities? Answer: You bet. How about a quarter of a million!

The two guys from Crucial one of them a tester told us there are about 50,000 different computer systems out there. These are not different brands, but various models and designs — different mother boards, processors, input/output systems, etc. What’s a user to do? Well, once again, you go to the web.

The Crucial.com website has a “Memory Advisor Tool.” Click it to begin. It’s not perfect, but it really cuts down on errors; their return rate on memory products is around one percent.

We have an old desktop machine that didn’t appear on their list, so we used the option to chat with an agent online. He gave us a link to a two gigabyte upgrade kit that was right for our machines. The cost to upgrade our five-year-old Compaq Presario was only $35. For the nine-year-old HP Pavilion the price was $92 The higher cost for the HP was because of its age; chips that match up with old computers cost more.

Most people get a new computer every four years, according to Crucial’s research. We have new laptops but have kept our old desktops. That’s because unless your speed requirement is very high someone working with movie editing, animation or huge databases, for instance, there is seldom a need to get a new computer; it’s bad for the environment and a waste of money, just add memory.

Digital memory is very cheap these days. For laptops, installation is as easy as sliding in the memory module. For desktops, plug the memory sticks into slots on the computer’s motherboard. Of course you have to take the case off a desktop computer to do this, and that scares some people away from the task, but there’s nothing dangerous about it if the computer is unplugged. To see how easy installing memory is, check out the tutorials at crucial.com/support/video.

We saw a huge speed improvement when we upgraded our old HP system from one to three gigabytes of RAM a few years ago. Another happy camper commented about her upgrade on the Crucial website and said that before that, it was constantly freezing, or crashing. The additional memory doesn’t just help everything run faster, it also lets you have several programs open at once, and boom, each one responds immediately.

By the way, Crucial is sponsoring a contest to find the owner and computer with the oldest relationship. If yours is older than nine years, you beat us. The prize is a new ASUS Eee Multi-touch Tablet PC tablet. To enter, go to crucial.com/research. If we win, we will donate our prize to a school or other worthy user.

A CURIOUS ASIDE: Crucial computer is owned by Micron, America’s largest maker of memory chips. Not surprisingly, that lets them get their supply at low cost. Micron was founded and financed by the late J.R. Simplot, who died just a few years ago. Simplot was an Idaho potato farmer who became wealthy supplying French fries to McDonald’s. So if you ever went into a McDonald’s and ordered fries, you helped improve computers’ memories.

Hit the play button on the image above or go to Youtube.com to walk inside a computer 20 times larger than normal. It was set up at Boston’s Computer Museum but is no longer there. The video is from 1990, but has inspired thousands to learn about computers. Search on “How Computers Work,” then take a walk through the computer.

When I was a lad, Bob says, there were repair shops for just about everything. If your radio or TV or blender, stopped working, you took it to a place that fixed those things. Nowadays, you just junk it and buy another.

No need, says the author. He tells you how to set up your own repair shop and describes the few tools you need and how to isolate problems. The examples include seemingly impossible to repair items like video recorders and DVD players. This is not for the faint of heart, but it’s not rocket science either.

“Snip, Burn, Solder, Shred,” by David Erik Nelson; $25 from No Starch Press, nostarch.com.

The subtitle on this book is: Seriously Geeky Stuff to Make With Your Kids.” So that points is in the direction we’re about to go and even sets the boundaries. Inside are lots of relatively small projects that children would find amazing and amusing, while at the same time learning something about basic physics and electronics. They range from making an indoor teepee for play, to building your own electric guitar.

This is going to cause some quick rewrites of scripts for crime shows and movies. You know the scene in which the master criminal gains access to the burglar alarm system and cuts the wires that activate it? Well that won’t work here, because this system has no wires.

The author tells us how to set up systems using all kinds of sensors tied together by the ZigBee wireless protocol, Xbee radio boards, and Arduino processors from Italy. What, you didn’t understand a word of that? (Well, you got some of the words.) Don’t worry, we didn’t either. But after a few pages, you’re in and up and running. By the time your halfway through, you’re dangerous.

Go to Allrecipes.com and click “Create a Recipe Box.” They’ll ask you to register, but it’s free. One of the choices is “add personal recipe.” Epicurious.com, which has recipes from Gourmet magazine, has the same option. Click “recipe box” and “add your own.” In either case, you can also add the site’s recipes to your box.

A savvy reader suggested sorting recipes into “tried and true” and “not tried.” Her favorite site: is Tastebook.com. It includes over two million recipes from all the top sites, including Better Homes and Gardens, The New York Times, Mayo Clinic, , Betty Crocker, Bon Appetit, Best Foods, 101 Cookbooks, Organic Valley, Land O’Lakes, Epicurious, Food Network, Gourmet, Heinz, Cooking Light, Ghiradelli Chocolate, Vegetarian Times and others.

Robot Controlled by Body Movements and Kinect

The Kinect sensor is Microsoft’s response to the success of Nintendo’s Wii machine. That has a motion sensitive controller and the game responds to its movements. With the Kinect and an Xbox 360, the game responds to your movements. This has led to some very interesting new developments.

Several smart young tech types have already figured out how to use the Kinect to draw in 3D, create 3D videos and control robots with their body movements.  We went to YouTube.com and watched Tomoto Washio transform himself into Ultra Seven, a Japanese superhero. He appeared to be shooting a stream of sparks and flames wherever he pointed his hand. He could also appear to detach a crescent from his hat, throw it, and have it return to the hat.

Using two Kinect sensors attached to the same Xbox, hacker Oliver Kreylos, was able to create holograms of himself. They can be rotated and as he turned you could see that the other side of his head wasn’t there. Another hacker used arm movements to make a small robot do push-ups.

To see these and others, go to YouTube.com and search on “Kinect 3D” or go to KinectHacks.net.  It’s just an amusement but we have the clear feeling that there’s something more going on here. We could certainly see future robots and robotic weapons directed by someone gesturing or making other motions from a distant point.

Somewhere, some place, all the time, there are people doing strange things with Lego blocks. In this case, we have an industrial designer in Germany who has put together some Lego guns. They are not deadly, since they fire only rubber bands or plastic Lego blocks, but you could still hurt someone if they hit an eye, so adults should watch over children’s play. Ninety percent of the book is filled with detailed drawings of the construction steps. The ultimate is a Lego assault rifle that can fire a stunning 1,200 rounds of Lego blocks a minute.