Make: Electronics by Charles Platt (read me a book .TXT) 📕

detects the high or low voltage on each pin of a chip, and reveals pulses that may occur too quickly for you to perceive them with the unaided eye.

Supplies

Integrated circuit chips

If you buy everything on this shopping list, and you bought basic parts such as resistors and capacitors that were listed previously, you should have everything you need for all the projects in this chapter.

As chips are quite cheap (currently around 50 cents apiece), I suggest you buy extras. This way, if you damage one, you’ll have some in reserve. You’ll also have a stock for future projects.

Please read the next section, “Fundamentals: Choosing chips,” before you begin chip-shopping. Chips should be easily obtainable from all the major electronics retail suppliers, and sometimes are found on eBay shops. Look in the appendix for a complete list of URLs.

Fundamentals

Choosing chips

Figure 4-2 shows what is often referred to as an integrated circuit (IC). The circuit is actually etched onto a tiny wafer or “chip” of silicon, embedded in a black plastic body, which is properly referred to as the “package.” Tiny wires inside the package link the circuit with the rows of pins on either side. Throughout this book, I will use the word “chip” to refer to the whole object, including its pins, as this is the most common usage.

Figure 4-2. An integrated circuit chip in Plastic Dual-Inline Pin package, abbreviated PDIP, or, more often, DIP.

The pins are mounted at intervals of 1/10 inch in two rows spaced 3/10 inch apart. This format is known as a Plastic Dual Inline Package, abbreviated PDIP, or, more often, just DIP. The chip in the photograph has four pins in each row; others may have many more. The first thing you need to know, when shopping for chips, is that you’ll only be using the DIP package. This book will not be featuring the more modern type, known as “surface-mount,” because they’re much smaller, more difficult to handle, and require special tools that are relatively expensive. Figure 4-3 shows a size comparison between a 14-pin DIP package and a 14-pin surface-mount package. Many surface-mount chips are even smaller than the one shown.

Just about every chip has a part number printed on it. In Figure 4-2, the part number is KA555. In Figure 4-3, the DIP chip’s part number is M74HC00B1, and the surface-mount chip is a 74LVC07AD. You can ignore the second line of numbers and/or letters on each chip, as they are not part of the part number.

Notice in Figure 4-3 that even though the chips look quite different from each other, they both have “74” in their part numbers. This is because both of them are members of the “7400” family of logic chips, which originally had part numbers from 7400 and upward (7400, 7401, 7402, 7403, and so on). Often they are now referred to as “74xx” chips, where “xx” includes all the members of the family. I’ll be using this family a lot, so you need to know how to buy them. I’ll give you some advice on that without going into details yet about what the chips actually do.

Figure 4-3. The DIP chip, at the rear, has pins spaced 1/10 inch apart, suitable for insertion in a breadboard or perforated board. It can be soldered without special tools. The small-outline integrated circuit (SOIC) surface-mount chip (foreground) has solder tabs spaced at 1/20 inch. Other surface-mount chips have pins spaced at 1/40 inch or even less (these dimensions are often expressed in millimeters). Surface-mount chips are designed primarily for automated assembly and are difficult to work with manually. In this photo, the yellow lines are 1 inch apart to give you an idea of the scale.

Take a look at Figure 4-4, which shows how to interpret a typical part number in a 74xx family member. The initial letters identify the manufacturer (which you can ignore, as it really makes no difference for our purposes). Skip the letters until you get to the “74.” After that, you find two more letters, which are important. The 74xx family has evolved through many generations, and the letter(s) inserted after the “74” tell you which generation you’re dealing with. Some generations have included:

74L

74LS

74C

74HC

74AHC

And there are more. Generally speaking, subsequent generations tend to be faster or more versatile than previous generations. In this book, for reasons I’ll explain later, we are mostly using the HC generation.

Fundamentals

Choosing chips (continued)

After the letters identifying the generation, you’ll find two (sometimes more) numerals. These identify the specific function of the chip. You can ignore any remaining letters and numerals. Looking back at Figure 4-3, the DIP chip part number, M74HC00B1 tells you that it is a chip in the 74xx family, HC generation, with its function identified by numerals 00. The surface-mount chip number, 74LVC07AD, tells you that it is in the 74xx family, LVC generation, with function identified by numerals 07. For convenience we could refer to the first chip as a “74HC00” and the second chip as a “74LVC07” because, regardless of their different manufacturers and package sizes, the fundamental behavior of the circuit inside remains the same.

The purpose of this long explanation is to enable you to interpret catalog listings when you go chip shopping. You can search for “74HC00” and the online vendors are usually smart enough to show you appropriate chips from multiple manufacturers, even though there are letters preceding and following the term that you’re searched for.

Suppose a circuit requires a 74HC04 chip. If you search for “74HC04” on the website of a parts supplier, you may find versions such as the CD74HC04M96 by Texas Instruments, the 74HC04N by NXP Semiconductors, or MM74HC04N by Fairchild Semiconductor. Because they all have “74HC04” in the middle, any of them will work.

Just be careful that you buy the larger DIP-style package, not the surface-mount package. If the part number has an “N” on the end, you can be sure that it’s a DIP package. If there is no “N” on the end,