A water wheel transfers the motion of running water into a rotational force. An alternator transforms this rotational force into electricity. You can power a light bulb with a water wheel if you have a source of running water. The water wheel can never produce enough energy to power the water running through it, so unless you have a natural source of running water, you won't generate extra energy with this project. Pair a water wheel with a rain barrel collection system or a stream to maximise its effectiveness.
Design your water wheel and mount on paper, based on the available water resource and site available for the wheel. The water source's flow, the speed and amount of water that moves through the source in a given time and the head -- the height of the water flow when it reaches the water wheel, also called a generator -- help determine how big your water wheel should be. The system needs to output at least 2 watts of power, the amount needed to power an LED light bulb. An incandescent light bulb requires 60 watts. The table on the Water Wheel Place website has approximate gallon per minute specifications for a water source running through a given pipe size that should give an idea of how many rotations per minute you can expect. Use this table as well as the calculator on the website to determine the diameter of your water wheel. At 25 gallons per minute, for example, the water wheel diameter is 1 foot.
Measure and cut two circles of 1/2 inch-thick wood to be the wheels of the water wheel. Make the circles the diameter found in the previous step. Drill a hole through the centre of each circle to insert the spinning axle rod. If your water wheel has to be longer in diameter than any available wooden sheets, in addition to cutting two 1 foot-diameter circles, assemble a larger circle from smaller sheets of wood. Subdivide the circumference of the circle into five equal parts in your paper design. Draw tangents from these points on the circumference to the centre of the circle. Connect each line you just drew to the lines on either side of it in the image with straight tangent lines. Make these lines form equilateral triangles, with one point being the centre of the circle, and the two other points being points on the two intersecting lines that run through the centre. Cut the resulting shapes out of wood to assemble together to form the larger circle for your water wheel. Nail the larger circle to the smaller circle, through which the spinning axle goes, with wooden slats.
Nail or bolt the metal hub plate to the centre of each circle of the water wheel.
Measure 12 equidistant points on the circumference of the water wheel circles. Draw straight lines from these points intersecting the centre of the circle. Measure and cut 12 wooden sheets with a width of at least 1 foot. Lay one of the water wheel circles flat on your workbench or work floor. Glue the slats perpendicularly to the plane of the circle and overlapping the tangent lines running from the circumference to the centre. Nail these wooden slats into both circles when the glue has dried. Stain the wood to protect it from water rot.
Build a wooden two-column mount for the water wheel. Make each column more than half as high as the water wheel's radius. Nail the wooden columns to a base for stability. Drill a hole at the same level and vertical position on each of the two columns. Nail a wooden shelf to one column below one of these holes. This shelf is for the electric generator. Stain the wooden mount to protect it from rot.
Grease the metal axle rod. Insert the rod through the metal hubs of the water wheel. Insert the two ends of the rod through the holes of the columns. Thread one metal cap over the end of the rod on the side of the column that does not have the generator mount.
Connect the shaft of the alternator to the axle of the water wheel. Only connect an alternator that has a low rotations per minute requirement to generate its expected voltage output. If the rotations per minute requirement of the alternator is higher than the rotations per minute of the water wheel, insert a gear and pulley system between the water wheel axle and the alternator to increase the rotations of the shaft of the alternator in relation to the shaft of the water wheel. Mount the alternator to the wooden shelf with duct tape, bolts or plastic or metal straps.
Wire the alternator to the hydro charge controller. This device prevents the alternator from dumping too much power into the battery even when the battery is full. Depending on the covering of the charge controller, it may need to be water-sealed with plastic or a wooden barrier to prevent water sloshing onto it.
Wire the 9V battery in its battery clip to the negative power terminals of the charge controller. Wire the positive terminal of the battery to the resistor. Wire the resistor to the LED. Mount this assembly in a plastic box or other small holding container and glue it to the shelf.
Set the water wheel mount in the path of the water source. Watch the light bulb turn on.