Beginner's Guide to Reading Schematics

Metadata

• Author: Stan Gibilisco
• Full Title: Beginner's Guide to Reading Schematics
• Category: #books

Highlights

• other circuit elements depend on it for proper operation. A transistor can act as a switch, an amplifier, an oscillator, or an impedance-matching device. A single, specific transistor can serve any one of these purposes. (Location 190)
• the remainder of the circuit in observance of the proper polarity. That means the positive capacitor electrode must go to the more positive DC voltage point in the circuit, and the other electrode must go to the more negative DC voltage point in the circuit. FIG. 3-11. Schematic symbol for a polarized capacitor. The side with the plus sign (+) should carry a positive voltage relative to the other side. Tip Polarized capacitors have external markings that tell you the polarity. Some have a plus sign, and some have a minus sign, and a few have both. Often, you’ll need a magnifying glass to resolve the symbols, so beware: You should never connect a polarized capacitor the wrong way around! All the capacitors that we’ve seen so far have a fixed design. In other words, the components specified have no provision for changing the capacitance value, which is determined at the time of manufacture. Some capacitors, however, do have the ability to change value. These components are generally called variable capacitors, although some specialized types are known as trimmer capacitors or padder capacitors. Figure 3-12 shows the most common symbol for a variable capacitor. An arrowed line reveals the variable property; it runs diagonally through a fixed capacitor symbol. Figure 3-13 shows two alternative ways of indicating this same component. Most of the time, the symbol shown in Fig. 3-12 will indicate a variable capacitance, regardless of the physical construction details. FIG. 3-12. Standard symbol for a variable capacitor. The curved line represents the rotor, and the straight line represents the stator. FIG. 3-13. Alternate symbols for variable capacitors. At A, the stator is not distinguished from the rotor; at B, the rotor appears as a curved line with an arrow. An air variable capacitor (one with an air dielectric) can tune many types of radio-frequency (RF) equipment including antenna matching networks, transmitter output circuits, and old-fashioned radios. A typical air variable has many interlaced plates, with the plates connected together alternately to form two distinct contact points. The set of plates that you can rotate is called the rotor; the set of plates that remains stationary is called the stator. All variable capacitors are nonpolarized components, meaning that the external DC voltage you connect to them can go either way and it doesn’t make any difference. Tip In most air variables, the rotor should go to electrical ground. The rotor connects physically to the shaft that you turn. By grounding that shaft along with the rotor, you minimize external capacitance effects so that if you touch the shaft, the addition of your body into the system doesn’t upset the performance of the circuit. In addition, you’re protected against the risk of electric shock when the shaft that you touch goes directly to ground! Sometimes, two separate variable capacitors are connected together or ganged in a circuit. In a ganged arrangement, two or more units… (Location 525)

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title: Beginner's Guide to Reading Schematics longtitle: Beginner's Guide to Reading Schematics author: Stan Gibilisco url: , source: kindle last_highlight: 2022-12-09 type: books tags:

Beginner's Guide to Reading Schematics

Metadata

• Author: Stan Gibilisco
• Full Title: Beginner's Guide to Reading Schematics
• Category: #books

Highlights

• other circuit elements depend on it for proper operation. A transistor can act as a switch, an amplifier, an oscillator, or an impedance-matching device. A single, specific transistor can serve any one of these purposes. (Location 190)
• the remainder of the circuit in observance of the proper polarity. That means the positive capacitor electrode must go to the more positive DC voltage point in the circuit, and the other electrode must go to the more negative DC voltage point in the circuit. FIG. 3-11. Schematic symbol for a polarized capacitor. The side with the plus sign (+) should carry a positive voltage relative to the other side. Tip Polarized capacitors have external markings that tell you the polarity. Some have a plus sign, and some have a minus sign, and a few have both. Often, you’ll need a magnifying glass to resolve the symbols, so beware: You should never connect a polarized capacitor the wrong way around! All the capacitors that we’ve seen so far have a fixed design. In other words, the components specified have no provision for changing the capacitance value, which is determined at the time of manufacture. Some capacitors, however, do have the ability to change value. These components are generally called variable capacitors, although some specialized types are known as trimmer capacitors or padder capacitors. Figure 3-12 shows the most common symbol for a variable capacitor. An arrowed line reveals the variable property; it runs diagonally through a fixed capacitor symbol. Figure 3-13 shows two alternative ways of indicating this same component. Most of the time, the symbol shown in Fig. 3-12 will indicate a variable capacitance, regardless of the physical construction details. FIG. 3-12. Standard symbol for a variable capacitor. The curved line represents the rotor, and the straight line represents the stator. FIG. 3-13. Alternate symbols for variable capacitors. At A, the stator is not distinguished from the rotor; at B, the rotor appears as a curved line with an arrow. An air variable capacitor (one with an air dielectric) can tune many types of radio-frequency (RF) equipment including antenna matching networks, transmitter output circuits, and old-fashioned radios. A typical air variable has many interlaced plates, with the plates connected together alternately to form two distinct contact points. The set of plates that you can rotate is called the rotor; the set of plates that remains stationary is called the stator. All variable capacitors are nonpolarized components, meaning that the external DC voltage you connect to them can go either way and it doesn’t make any difference. Tip In most air variables, the rotor should go to electrical ground. The rotor connects physically to the shaft that you turn. By grounding that shaft along with the rotor, you minimize external capacitance effects so that if you touch the shaft, the addition of your body into the system doesn’t upset the performance of the circuit. In addition, you’re protected against the risk of electric shock when the shaft that you touch goes directly to ground! Sometimes, two separate variable capacitors are connected together or ganged in a circuit. In a ganged arrangement, two or more units… (Location 525)