Ultra-Low-Power, Locally-Mirrored Wikipedia
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the System Above is Charged Via the System below
Enter The Pi
The Raspberry Pi is an exciting platform for a lot of reasons. One of them is a full linux stack consuming only 5V @ 1Amp. If the power goes out, we want to arm ourselves with information. The Pi is a mightily efficient tool for this.
We did not want to assume a user has access to another working, network-enabled device. Therefore, the pi should have its own, reasonably useable IO. Moreover, this IO should require as little power as possible, but still present actually readable output. Enter the Kindle.
Extremely Efficient IO
Electronic Ink, or E-ink, has the capability to hold static text and images indefinitely without using electricity. Once information has been rendered to the screen, it no longer draws power. We believe this to be the least-energy-intensive approach to this challenge. The Usb connection between the Kindle and the Pi provides power and data back and forth, forever.
Design Decisions, ContinuedThe design of the project and selection of components was based on these assumptions:
- The system must be energy efficient;
- The project will not be costly and could be easily duplicated;
- Will be made of DIY parts when possible;
- The system will be versatile and semi-mobile;
We decided not to use a more general ac/dc inverter because it is inefficient ; the inverter draws power to activate its internal fan. The circuits built are an efficient way to transfer DC power from the battery to DC power to the Pi as there is less loss in the process. Also, we wanted to learn how to build them ourselves.
The 7815 in the Above Circuit was chosen for its ability to safely charge the battery, providing a safe difference between the bicycle generated Voltage and the battery's maximum charging Amperage.
Analog Voltmeters and Amp meters allow for energy-system information at low-energy-cost
We used the Kindle 3 because it uses the e-ink technology which does not need to refresh, therefore it uses a very low power draw. The Raspberry PI is also very energy efficient.
WiKiPi is fairly transportable, drawing power from a small 12 volt lead acid battery. The project, powered by a person, can work both outside or inside.
Versatility + Next Steps
We recognize that this system can be configured for (a) Multiple Power Sources (b) Multiple Software Stacks - I.E. Solar-powered Bulletin Board Systems. We're interested in circuits can be used with other power sources. Therefore solar power could be safely exchanged for the bicycle-generator of a wind turbine.
A ton of guidance from the following :
- How to Mirror Wikipedia : Installing Wikipedia on Raspi
- Kindle Via Pi : How to use Kindle 3 Screen as a Low Power Terminal & Display
- Bash Script to Access Wikipedia : Some work went into modifying this for localhost, but not much else. This is needed to see Wikipedia Output on K3 Screen (Lynx doesn't work)
- Original Kindleberry Pi : Kindle + Pi Origin