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own power cord. Fortunately, I noticed my mistake before the soldering iron melted much of the power cord’s insulation.Make sure the soldering iron’s power cord is placed safely away from your stuff so that you won’t bump it as you work, knocking it out of its stand and perhaps causing a burn. Be sure to wear eye protection when you solder. As solder melts, it occasionally boils and splatters little globules of hot solder through the air. You really don’t want molten metal anywhere near your eyes.

       Electronics — and especially soldering — can also create a chemical hazard. When you solder, small amounts of lead are released into the air. Therefore:Always work in a well-ventilated place.Wash your hands after you work with solder or any other electronic components before you touch your face, mouth, nose, or eyes. Small amounts of lead and potentially other toxic substances are bound to get on your hands. It’s best to wash them frequently to keep whatever gunk they pick up from getting into your body.Keep your soldering tools away from children. Young children and pets love to stick things in their mouths. If you leave solder or little electronic parts like resistors or diodes sitting loose on top of your workbench, your kids or pets may decide to make a meal of them, so keep such things safely stored in boxes or cabinets and, if possible, keep your entire work area safely off-limits and behind closed doors.Don’t get into the habit of sticking parts into your mouth to hold them while you’re working. As crazy as it sounds, I’ve seen people hold a dozen resistors in their mouth while soldering each one into a printed circuit board. That’s definitely a bad idea.

       Working with sharp tools such as knives, wire cutters, and power drills creates a risk of cutting injury. Therefore:Think before you cut. Make sure you know exactly where you want to make the cut, and make sure you know exactly where all your fingers are before you start the cut.Let the tool do the work. Don’t apply excessive force to coerce a tool into making a bigger, deeper, or wider cut than it’s designed to do.Keep your tools sharp. Working with dull tools causes you to use extra force, which often results in the tool slipping and finding itself lodged in your finger.Remove jewelry such as rings, wristwatches, and long dangling necklaces before you start — especially if you’re working with power tools.Wear safety goggles whenever you’re cutting, sawing, or drilling. Little pieces of the work or blade can easily break off and hit you in the face. Add bits of insulation, copper wire, and broken drill bits to the growing list of things you don’t want in your eyes.

Keeping Safety Equipment on Hand

      In spite of every precaution you might take, accidents are bound to happen as you work with electronics. Other than preventing an accident from happening in the first place, the best strategy for dealing with an accident is to be prepared for it, so I recommend you keep the following items nearby whenever you’re working with electronics:

       Fire extinguisher: So you can quickly put out any fire that might start before it gets out of hand.

       First-aid kit: For treating small cuts and abrasions as well as small burns. The kit should include bandages, antibacterial creams or sprays, and burn ointments.

       Phone: So that you can call for assistance in case something goes really wrong.

       Friend: If your project works with household current (120 volts), a friend can help in case you get shocked.

Protecting Your Stuff from Static Discharges

      Static electricity — more properly called electrostatic charge — results when electric charges (that is, voltage) builds up in the absence of a circuit that allows current to flow. Your own body is frequently the carrier of static charge, which can be created by a variety of causes. The most common is friction that results from simple things such as walking across a carpet. Your clothes can also pick up static charge, and usually do when you toss them around in a clothes dryer.

      Static charge accumulated in your body usually discharges itself over time. However, if you touch a conductor — such as a brass doorknob — while you’re charged up, the charge will dissipate itself quickly in an annoying shock.

      If the conductor happens to be a sensitive electronic component such as a transistor or an integrated circuit rather than a brass doorknob, the discharge can be more than annoying; it can fry the innards of the component, rendering it useless for your projects. For this reason, it’s wise to protect your stuff from static discharge when you work on your electronic projects. The easiest way to do that is to make sure you’re properly discharged before you start your work. If you have a metal workbench or a large metal tool such as a drill press or grinder near your workbench, simply reach out and touch it after you’ve settled in to your seat and before you begin your work.

A more reliable way to protect your gear from static discharge is to wear a special antistatic wristband on one wrist, as shown in Figure 4-2. Wear the wristband tightly so that it’s in good solid contact with your skin all the way around your wrist. Then, plug the alligator clip into a metal surface such as your workbench frame or that nearby drill press.

      FIGURE 4-2: An antistatic wristband.

       For best results, the alligator clip on your antistatic wristband should be connected to a proper earth ground. To create a proper earth ground, clamp a long length of wire to a metal water pipe. The wire should be long enough to reach from the pipe to your workbench. Carefully route the wire from the pipe to your workbench, strip off an inch or so of insulation, and staple or clamp the wire to the workbench, leaving the stripped end free so you can attach the alligator clip from your antistatic wristband to it. (Note that this technique works only if the building uses metal pipes throughout. If the building uses plastic pipe, the water-pipe won’t provide a proper ground.)

       An often-recommended way to connect the wristband to an earth ground is to connect it to the ground receptacle of a properly grounded electrical outlet. I’m definitely not a fan of this method, as the key to its operation lies in the term “properly grounded electrical outlet.” All it takes is one stupid wiring mistake, or one wire shaken loose by a sonic boom or a mild earthquake, and suddenly that ground wire might not be a ground wire anymore — it might be energized. Call me paranoid if you wish, but there’s no way I can recommend strapping a conductor around your wrist and then plugging it into an electrical outlet.

Chapter 5

      Reading Schematic Diagrams

      IN THIS CHAPTER

       Examining how schematic diagrams provide a road map for electronic circuits

       Looking at the most commonly used component symbols

       Noting how voltage supply and common ground circuits are often drawn

       Seeing how components are typically labeled

      I love maps. I think I’ve kept every map I’ve used on every trip I’ve taken. I have big maps of entire countries and states, maps of cities, walking maps, maps of parks and museums, and even subway maps. My favorite maps are topographical maps of the areas where I’ve gone on weeklong backpacking trips. These maps show

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