Raspberry Pi basically runs on Linux which takes time to start once powered. If you have designed some hardware solution which controls valuable things, you probably don’t want it to fail on power failures. Like for desktop computers there UPS used, same technique can be applied to Raspbbery Pi. The only difference is scale of things. Juice4halt shares Raspberry backup power solution. He uses couple supercapacitors for energy storage.
Since supercaps are low voltage like 2.7V there is step-up/down circuit needed to take care of charging and draining power. He made whole power board that sits on top of Raspberry Pi. It carries two independent Ds/Ds converters where on is used for charging supercaprs in step-down mode and powering board from them through step-up converter. Another DC/Dc converter is used as front end step-down converter which converts input voltage in to 5.1V. This is convenient for using any wall DC adapter. With two 25F 2.7V supercaps and 375mA constant current draw on Raspberry Pi it is capable to supply for about 61second. So it can withstand short power failures. If you need longer times, probably adding more supercaps should help or think of normal UPS.
Python is popular programming language used in Raspberry Pi. It is easy, intuitive and well documented. With Raspberry Pi hardware you can access physical pins and do lots of crazy things. Anyway like any new thing you need to learn it. TO make thing much easier, jechavarria introduced Rpi board which is dedicated for learning Python on Raspberry Pi.
Rpi board has four 10mm diffused LEDs – each different color. Each is controlled through Mosfet transistor key. Then there are couple push buttons that are lined with LEDs and in the middle there is a buzzer which is also driven through transistor key. On top of it Rpi board carries 2×16 LCD. Additionally you can see I2C buss connector for future extensions and. Couple green LEDs on a side are just for indicating 3V and 5V power supply. Rpi board mounts on top of Raspberry Pi model B (or A) and should fit on B+ model. He also provides few Python code examples to get started with.
Raspberry Pi is a Linux machine, so it meant to be web accessible. One thing is to connect to internet from it and another is to run web server on it. Depending on what WWW features you want there are many options to do so. But probably most common way of serving websites is with PHP and MySQL. To get all of this working, there are several preparations required on Raspberry Pi. Drcurzon have shared his experience on instructable.
He thought that Raspberry Pi is low power device, so it can be turned on all time and serve as small webserver for non heavy loads. After initial RasPi setup he installed all component including Apache with PHP then MySQL and FTP for easy access and update web contents. phpMyAdmin for easy database managing. Each component requires user and password setups that are explained in instructable. If you follow all steps you should have your webserver up and running.
Computer monitor is pretty strict device – is displays information withing its frame. Outside and behind its dark. To change that Sebastien has been working on several versions of SlightBox projects where it allows playing light effects behind screen that extends on-screen effects and somewhat removes limits between screen and outside world.
Video demonstration speaks for itself. Watching movies and playing games become different with those effects. The heart of this system is Raspberry Pi which does video signal analysis and determines color pixels from captured frames. Python script uses OpenCV library to do this task. Once color data is gathered, it is sent over SPI to LPD8806 LEDs behind screen. Since analyzing HDMI signals is quite tricky, he split HDMI signal where one was converted to S-video which then was fed to Raspberry Pi with STK1160 adapter. Raspberry pi also has a standard LCD for fast control and monitoring parameters. Infrared channel allows remote control of SlightBox. Raspberry Pi also allows configuring devices via web interface. So this is fun device that vivid and extend any HDMI screen at your house. Fun guaranteed. (translated source)