How To Build Permanent Magnet Alternator?

Does anyone know how to build a small alternator?

• I am doing some experiments with green energy and would like to know how to build a eco-friendly power source for small electric objects. if anyone could tell me how its made and why it works that'd be excellent.

• Answer:

  A simple way to generate electricity is to take a permanent magnet hobby motor and spin its shaft. A motor consumes electric energy to produce mechanical energy, while a generator consumes mechanical energy and produces electrical energy. Basically the only difference between a motor and generator is the direction of power flow. Mechanical => Electrical or Electrical => Mechanical Not all motors are capable of creating electricity by just spinning the shaft. As you correctly pointed out not all motors have permanent magnets and require power to establish magnetic fields. The hobby motor available from Radio Shack is a DC motor and will produce pulsating DC. DC motors (and Generators) use a commustator to switch the output polarity of the power being generated as the generated power is starting to change direction. All generators produce AC in their windings, it is the Conversion of AC to DC by rectification or commutator switching that creates DC power. Alternators use slip rings and maintain the same polarity of electrical connections to the windings (no switching ocurrs). This allows the AC created in the winding to flow directly to the output connections as AC. In a car alternator a series of diodes are used in a full wave rectifier configuration to convert the AC into DC. A stepper motor can be used to easily generate AC as it doesn't have a commutator. Beaware that the frequency of any AC you generate will be dependant upon the speed that the shaft is turned and the number of poles inside the motor/generator. You can minimize power line transmission losses by using AC just like the power companies do and then convert the AC to DC to charge batteries. Then use an inverter to convert the battery DC into usable AC power. For a small semi practical homebrew windmill consider the ability to charge a few small rechargable AA batteries an accomplishment. Beaware that you will need to use a diode when charging batteries to prevent battery current from backflowing into the generator and motorizing it. You want your generator to porduce power and not consume it. Using rectifiers in an AC generator would provide this blocking capability but using DC motors or solar cells will require the addition of at least one diode to prevent current backflow when the generator isn't producing enough power. (no wind for windmill or no sun for solar cell)