Our assignment was to apply a reversed dc permanent magnet motor generator to something, so to create something you can manually power.
I decided to use a roll up shade. In our classroom there are very large shades that are open and closed by pulling on a circular chain. Therefore the power is transferred from the spinning rod to the vertical chain going up and down, which means that by a simple pull of the chain the rod will spin very quickly.
I used a tape player, because in the play position it is always on. It is really easy to make a tape player play and stop by adding and removing power. With the curtain I was able to produce just the right amount of power, so that while the curtain was being taken up or lowered, Let it Be would play.
Probably the most interesting thing I learned in this class is that a motor is a generator in reverse. For example, a DC permanent magnet motor turns as a result of permanent magnets repelling and attracting the router coil – an electromagnet created by winding a powered coil around a piece of metal and infusing it with the energy of the battery. If you reverse the poles of the battery the motor will spin in the opposite direction.
If you were to take the motor and spin the part that is generally spinning, the reaction happens in reverse, and power is released through the wires usually going to a battery. Reversing the direction of the spin switches the poles (negative/positive). If you are powering something and you want it to work when the motor spins in either direction, as was the case in my project, you would want to include a bridge rectifier, also used to convert ac to dc power, to redirect the current and keeps it flowing in one direction.
Bridge Rectifier