Why would anyone want an FTP server and that too powered by the sun? Well, with an FTP server, you can access all your digital files from anywhere with an internet connection. The sun-powered bit has two advantages, the sun charges those standby batteries and the expense does not show up in your utility bills.

For the project all the parts used are standard items. The Single Board Computer used is the Raspberry Pi (RBPi), a convenient case with all the right slots for the output ports and a small solar panel. Additionally, you will also need a solar charger and a battery box to house the four AAA sized rechargeable NiMH batteries and a micro-USB cable.

A word about the solar panel; you can buy the solar panel from Cottonpickers. The advantage is you get a solar panel with a built-in battery box and a box for the RBPi together. All you have to do is to slide in the RBPi and plug in the batteries. This model has an on/off switch, so you do not have to pull out the cord to switch off. The batteries keep charging even with the switch in the off position.

A blue LED on charger lights up when the sun is charging the batteries. There is also a USB socket, which you can use for charging other USB devices such as mobile phones. Cottonpickers also supplies a USB cable along with the solar panel, so you have almost everything you need for the project.

The solar panel supplies a little more than 300mA, which means that it is perfect for charging 3000mAH NiMH batteries, since they require a C/10 charging rate. The panel has blocking diodes to prevent the batteries from discharging through the cells.

The RBPi model B, with all its keyboard, mouse, TV and networking plugged in and running consumes about 400mA, which the solar panel can easily meet if the sun is shining in its full glory. When the sun goes down, the battery takes over seamlessly. The solar panel can fully charge four AAA cells of 750mAH capacity within three hours. This allows an operation time of more than one and a half hours on the battery.

Charging four AA cells rated at 3000mAH takes the panel about 10 hours to complete. That means if the panel is left in the sun the whole day, the battery will be fully charged for the night. The options you have are:

Powering your RBPi directly from the sun and use the four NiMH cells as a buffer when the sun hides behind clouds. Let the solar panel charge the battery of cells during the day and you can use your RBPi at night.

Next, you will need a static IP address. This is essential, as the address will let your network firewall know it has to allow incoming FTP requests from there. You will also need a vnc-server and load it up as a service every time the RBPi boots up. For the FTP, use the Very Secure FTP Daemon or VSFTPD. Setup all the software as per the instructions found on CNET and you are ready to go. Don’t forget that your RBPi needs a lot of sunshine!

People who have grandmothers (and grandfathers) are fortunate. Although most of these old people are healthy and strong despite their advancing years, not all are so lucky and may be impaired in some way, mostly because of their failing eyesight and trouble with arthritic hands. Since they have a physical handicap, they find it difficult to operate a laptop, a DVD player or a tiny MP3 player. A Raspberry Pi (RBPi) with a large play button is actually helpful if it can read back an audio book.

This can be done in two ways. The RBPi player can have a single large button to pause and play, or have no buttons at all and be operated by NFC tags. The tags are best attached to empty CD or DVD cases, on which the details of the Audio book are printed in large letters for easy reading. Simply passing a case over the player will cause the specific audio book to start playing from its last state.

The player saves its state after every two seconds. Therefore, when the listener is bored or otherwise wants to stop listening, he or she can simply disconnect the player from its mains socket. Reconnecting it allows the player to get back to playing from its last saved state.

The RBPi player with a single large button works as a play/pause button when pressed. Going back to the previous track is easy if the listener holds the button pressed for more than four seconds. Copying files into the player is also a simple affair with a thumb drive. The files are copied into the thumb drive under a special volume label. As soon as it is plugged into the RBPi USSB port, the books are copied into the SD card and starts playing when the drive is unplugged.

For the single button RBPi player, apart from the RBPi and its enclosure, you will need a blue LED, some wires, a pair of speakers and of course, the large button. Among the software that you will need are – Raspbian image (Wheezy), mpd, mps, mpd-python, pyudev and a python script.

When the RBPi player is first powered up, it boots, starts the python script and waits with the audio book in pause. Since at a time only one audio book is stored, pressing the button starts the player. If the button is held pressed by more than four seconds, the player goes back one track. The player always remembers its last playing position.

As soon as a USB thumb drive is plugged in, the player stops playing, mounts the thumb drive, deletes the old audio book, copies the new one from the special name/label on the thumb drive and rebuilds the playlist. A flashing blue LED signals the end of file copy. Once the thumb drive is removed, the new audio book starts in pause mode, proceeding to play when the play/pause button is pressed briefly once.

Use of mpd allows the RBPi player to support wave, Musepack, MOD, MP4/AAC, MP3, MP2, OggFLAC, FLAC and Ogg Vorbis file formats.