tailieunhanh - Practical Arduino Cool Projects for Open Source Hardware- P43

Practical Arduino Cool Projects for Open Source Hardware- P43: A schematic or circuit diagram is a diagram that describes the interconnections in an electrical or electronic device. In the projects presented in Practical Arduino, we’ve taken the approach of providing both a photograph and/or line drawing of the completed device along with a schematic. While learning to read schematics takes a modest investment of your time, it will prove useful time and time again as you develop your projects. With that in mind, we present a quick how-to in this section | CHAPTER 16 RESOURCES Figure 16-12. Using mains to provide accurate 50 60Hz reference Inexpensive DIY Prototyping Shields One of the most annoying idiosyncrasies of the physical design of standard Arduino boards is that the header connections for plugging in a shield don t sit neatly on a standard grid the top two headers are spaced 160mil apart which makes it impossible to create a shield using a cheap piece of standard stripboard or perfboard with male breakaway headers soldered on. To get around this problem there are some really neat prototyping shields available from a number of suppliers including Adafruit Industries Seeed Studio SparkFun and many others. Figure 16-13 shows popular protoshield from SparkFun. Commercial prototyping shields vary in features. Some include stackable headers or an extra reset button so it s easily accessible with the shield mounted on an Arduino or status LEDs or mounting pads for surface-mount chips. For most projects a commercial prototyping shield will do just what you need. Figur e 16-13. A simple prototyping shield 399 CHAPTER 16 RESOURCES But it would have been nice if the Arduino design had the shield headers on a consistent grid so that if you just wanted to grab a piece of inexpensive stripboard and put some male breakaway headers on it you could plug it straight in. All is not lost though Luke Weston has come up with a simple way to modify an Arduino so that you can do exactly that. Start by finding an 8-pin female PCB header either from an electronics parts supplier or included in a commercial prototyping shield kit then hold it beside the regular digital I O pin 8-13 header on your Arduino so that the pins protrude down beside the Arduino PCB. Then slide it along slightly toward pin 13 so that the horizontal spacing between the first pin next to pin 8 on the new header and the existing pin 7 on the old header is exactly inches . twice the distance between two header pins. A tiny drop of .