Building a project with an Arduino is one thing, but powering it can be quite another. Batteries work, naturally, but need to be replaced; solar panels are one solution to keeping them topped up, but Danja Mewes has another: bicycle power.
In her latest Instructable, Danja explains how to build an Arduino-based water purification system. Using an ultraviolet light to kill any nasties in the water, along with a pump and filter to remove particles you don't want to drink, Danja's system relies on a hefty battery mounted in the rear basket of the bike for its power.
The battery, meanwhile, gets its power from a dynamo attached to the rear wheel of the bike. Familiar to readers of a certain age as the method by which bicycle lights used to work - for certain values of 'work' which include 'going off when you stop,' at least - the dynamo translates some of the energy going into making the wheel spin into electricity which can be used to trickle-charge the battery ready for when it's needed.
The Arduino at the heart of the build, meanwhile, provides the controlling logic and a liquid crystal display (LCD) for checking the water level is sufficient before activating the UV lamp through a relay. The purification system is the latest in a stream of bicycle-related projects created by Danja, who is currently working to build an energy-harvesting playground using recycled bicycle parts.
This Instructable demonstrates how to power a UV-C water purification system with a bicycle and Arduino control. A dynamo in the rear of the bicycle charges a battery that runs the arduino and the light. An additional optional step demonstrates how you would add a pump and filter to the system through a second bottle.