Tài liệu Amphibionics P2 doc

quick-setting epoxy (T) to secure parts. Safety glasses (U) should be worn at all times when cutting and drilling metal or soldering. Test Equipment To calibrate and troubleshoot the electronics, you will need a dig- ital multimeter with frequency counting capabilities, similar to the Fluke 87 multimeter (Figure 1.14, left). When working with elec- tronic circuits, a good multimeter is invaluable. The second multi- meter in Figure 1.14 (right) is manufactured by Circuit Test and measures capacitance, resistance, and inductance. It is nice to be able to measure the exact values of components when working on precise circuits, but in most cases, this is not necessary. If you are winding your own transformers or chokes, the ability to measure inductance will be helpful. The specific use of the multimeter will be explained during the construction of the robot’s electronics in later chapters. Amphibionics 10 FIGURE 1.14 Fluke and Circuit Test multimeters. Amphibionics 01 3/24/03 8:01 AM Page 10 If you are really serious about electronics, then an oscilloscope, like the one pictured in Figure 1.15, is a great investment. This is the Tektronix TDS 210 dual channel, digital real-time oscilloscope, with a 60-MHz bandwidth. The TDS 210 on my bench also has the RS-232, GPIB, and centronics port module added, so that a hard copy of waveforms can be output. The great advantage to using an oscilloscope is the ability to visualize what is happening with a circuit. The new digital oscilloscopes also automatically calculate the frequency, period, mean, peak to peak, and true RMS of a waveform. You will probably need to use a regulated direct current (DC) power supply and a function generator quite often as well. None of the equipment shown in Figure 1.15 is required when building the robots in this book, but it will make your life as an Chapter 1 / Tools, Test Equipment, and Materials 11 FIGURE 1.15 Oscilloscope, regulated DC power supply, and function generator. Amphibionics 01 3/24/03 8:01 AM Page 11 electronics experimenter much easier. There is nothing more frustrating than finding out that a circuit you are working on is malfunctioning because of a dead battery or an oscillator cali- brated to the wrong frequency. If you use a good power supply and oscilloscope when building and testing a circuit, the chance of these kinds of problems surfacing is much lower. I have always found that if I am working late at night and start to encounter a lot of small problems and make mistakes, the best thing to do is to shut my equipment down and get a good night’s sleep. Sometimes the difference between frying an expensive chip or the circuit’s working perfectly on the first try is just one mis- placed component. Construction Materials The robots in this book are constructed using aluminum and fas- teners that are readily available at most hardware stores. Five sizes of aluminum will be used. The first stock measures 1/2-inch wide by 1/8-inch thick, and is usually bought in lengths of 4 feet or longer. Many of the robot parts are constructed from aluminum, with the dimensions as shown in Figure 1.16. Amphibionics 12 FIGURE 1.16 1/2-inch by 1/8-inch aluminum stock. Amphibionics 01 3/24/03 8:01 AM Page 12 The second type of aluminum stock that will be used measures 1/4-inch ϫ 1/4-inch, and is shown in Figure 1.17. It is usually bought in lengths of 4 feet or longer as well. The third kind of aluminum stock is 1/2-inch ϫ 1/2-inch angle aluminum, and is 1/16-inch thick, as shown in Figure 1.18. The fourth type is 1/16-inch thick flat aluminum, as shown in Figure 1.19, and it is usually bought in larger sheets. However, most metal suppliers will cut it down for you. This thickness of aluminum is great for cutting out custom parts and it is easy to Chapter 1 / Tools, Test Equipment, and Materials 13 FIGURE 1.17 Aluminum stock with 1/4-inch by 1/4-inch dimensions. FIGURE 1.18 1/2-inch angle aluminum. Amphibionics 01 3/24/03 8:01 AM Page 13 bend, making it ideal for the hobbyist experimenter. I buy all of my metal from a company called The Metal Supermarket (www.metalsupermarkets.com) because its prices are much lower than buying metal at a hardware store. Their friendly staff is always helpful, and will cut the stock to whatever size you require. I usually ask them to cut the raw stock in half so that it will fit into the back seat of my car. The fifth type of stock that will be needed is 3/4-inch ϫ 3/4-inch angle aluminum. The fasteners that will be used are 6/32-inch diameter machine screws, nuts, lock washers, locking nuts, and nylon washers, as shown in Figure 1.20. Three different lengths of machine screws will be used: 1-inch, 3/4-inch, and 1/2-inch. Amphibionics 14 FIGURE 1.19 1/16-inch thick flat aluminum. Amphibionics 01 3/24/03 8:01 AM Page 14 Summary Now that all the tools, test equipment, and materials necessary to build robots have been covered, you should have a good idea about what will be necessary to build the robots in this book. In the next chapter, the fabrication of printed circuit boards will be discussed so that you can make your own professional-looking boards. Chapter 1 / Tools, Test Equipment, and Materials 15 FIGURE 1.20 6/32-inch diameter machine screw, lock washer, nuts, and nylon washer. Amphibionics 01 3/24/03 8:01 AM Page 15 This page intentionally left blank. 17 Four robot projects are in this book. Each robot will require a con- troller and sensor circuit boards. The most efficient way of imple- menting the circuit designs is to create printed circuit boards (PCBs). The great thing about each project is that the finished PCB artwork is included, along with a parts placement diagram. All of the circuit boards and robots in this book have been built and test- ed to ensure that they function as described. If you decide not to fabricate PCBs, most of the circuits are simple enough to construct on standard perforated circuit board (holes spaces 0.10-inch on centers) using point-to-point wiring if you wish. I don’t recom- mend this method because one misplaced or omitted wire can cause hours of frustration. The easiest way to produce quality PCBs is by using the positive photo fabrication process. To fabricate the PCBs for each robot proj- ect, photocopy the PCB artwork onto a transparency. Make sure that the photocopy is the exact size of the original. For convenience, you can download the artwork files for each robot project from the Thinkbotics Web site, located at www.thinkbotics.com, and print the file onto a transparency using a laser or ink-jet printer with a minimum resolution of 600 dpi. Figure 2.1 shows the artwork for a Printed Circuit Board Fabrication 2 Amphibionics 02 3/24/03 8:08 AM Page 17 Copyright 2003 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use. circuit board that has been printed onto transparency film using an ink-jet printer. After successfully transferring the artwork to a transparency, the following instructions can be used to create a board. A 4- ϫ 6-inch presensitized positive copper board is ideal for all of the projects presented in this book. When you place the transparency on the copper board, it should be oriented exactly as shown in each chapter. Make any sensor boards that go with the particular proj- ect at the same time. A company that specializes in providing pre- sensitized copper boards and all the chemistry needed to fabricate boards is M.G. Chemicals. Information on how to obtain all of the supplies can be found on its Web site: www.mgchemicals.com. Figure 2.2 shows the developer, ferric chloride, and presensitized copper board that will be used for fabricating the circuit boards. Amphibionics 18 FIGURE 2.1 PCB ar twork printed onto transparency film. Amphibionics 02 3/24/03 8:08 AM Page 18 Follow the next six steps to make your own PCBs: 1. Setup—Protect surrounding areas from developer and other splashes that may cause etching damage. Plastic is ideal for this. Work under safe light conditions. A 40-W incandescent bulb works well. Do not work under fluorescent light. Just prior to exposure, remove the white protective film from the presensitized board. Peel it back carefully. 2. Exposing your board—For best results, use the M.G. Chemicals cat. #416-X exposure kit. However, any inexpen- sive lamp fixture that will hold two or more 18-inch fluores- cent tubes is suitable. Directions: Place the presensitized board, copper side toward the exposure source. Positive film artwork should be laid onto the presensitized copper side of the board and positioned as desired. Artwork should have been produced by a 600-dpi or better printer. If you don’t have a printer that can handle 600 Chapter 2 / Printed Circuit Board Fabrication 19 FIGURE 2.2 Photo fabrication kit. Amphibionics 02 3/24/03 8:08 AM Page 19 [...].. .Amphibionics dpi, then make two transparencies and lay them on top of each other Make sure that the traces line up perfectly, and then staple them together A glass weight should then be used to cover the... drill bit to drill all the component holes on the PCB Drill the holes for larger components with a 3/64-inch bit where indicated Drill any holes that will be used to mount the circuit board at this 21 Amphibionics FIGURE 2.3 An etched board ready for drilling time It is best to use a small drill press, like the one shown in Figure 2.4, rather than a hand drill, when working with circuit boards This... discuss the specifics of how the microcontroller can be used as the processor for the various robots that will be built 25 Copyright 2003 by The McGraw-Hill Companies, Inc Click Here for Terms of Use Amphibionics PIC 16F84 MCU Microchip technology has developed a line of reduced instruction set computer (RISC) microprocessors called the programmable interface controller (PIC) The PIC uses what is known... able to jump right into this project The frog will be using all eight I/O lines of Port B and all five lines of Port A, as shown in Figure 3.2 FIGURE 3.2 Frogbotics main controller board schematic 27 Amphibionics Table 3.1 shows how the various pins of Port A and Port B will be used as inputs and outputs to control the different functions of the frog robot It is useful to have a list of the various . the robot’s electronics in later chapters. Amphibionics 10 FIGURE 1.14 Fluke and Circuit Test multimeters. Amphibionics 01 3/24/03 8:01 AM Page 10 If. with the dimensions as shown in Figure 1.16. Amphibionics 12 FIGURE 1.16 1/2-inch by 1/8-inch aluminum stock. Amphibionics 01 3/24/03 8:01 AM Page 12 The