tailieunhanh - Practical Arduino Cool Projects for Open Source Hardware- P15

Practical Arduino Cool Projects for Open Source Hardware- P15: 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.: A schematic or circuit diagram is a diagram that. | CHAPTER 7 ONLINE THERMOMETER If all went well you ll see a web page containing readings taken from each of the connected temperature sensors. Sometimes DS18B20 temperature sensors return bogus values the first time they are accessed after powering up so if the numbers look wildly wrong just hit refresh and you should see proper values come back. Variations The project as described runs a web server on the Arduino so you can poll it to access the current temperature readings. Alternatively you could run a web client on the Arduino in a loop so that every few minutes it reads from the temperature sensors connects to a web server and submits the values through as arguments in the URL to be stored or processed by a script on the server. Just remember that because of the lack of routing information available in the etherShield library the server would need to be on your local network. Alternatively you could run a local reverse proxy as a gateway so the Arduino thinks it s connecting to a local host but the request is actually being forwarded on to an external machine. That way you could use a third-party service such as Pachube or Watch My Thing to store and graph the data. 119 C H A P T E R 8 Touch Control Panel Small four-wire resistive touch screens are now amazingly inexpensive they are produced in such enormous quantities for mobile phones PDAs and particularly handheld games such as the Nintendo DS that they can be bought brand new for under US 10. Larger touch screens are also rapidly falling in price. The popularity of netbooks with screens between 7 and 10 inches in size has resulted in a healthy market for touch screens that can be retrofitted to them and plugged into an internal USB port. Despite the fact that they come with control electronics and a USB interface those screens are also predominantly four-wire resistive devices so if you dump the control module that comes with them and interface to the screen directly you