Electromechanical components are a particular class of devices that convert electrical energy into mechanical force or rotation. Relays, solenoids, and motors are three common electromechanical components that you should understand and be familiar with. Each of these important devices relies on the principles of electromagnetism.
The Main Components which are used in Common Printer is as Follows :
Electromagnetism
Whenever electrical current passes through a conductor, a magnetic field is generated around the circumference of that conductor as shown in 2-9. Such a magnetic field is capable of exerting a physical force on permeable materials (any materials that can be magnetized). The strength of a magnetic field around a conductor is proportional to the amount of current flowing through it. Higher amounts of current result in stronger magnetic fields, and vice versa. Unfortunately, it is virtually impossible to pass enough current through a typical wire to produce a magnetic field that is strong enough to do any useful work. The magnetic field must somehow be concentrated. This is accomplished by coiling the wire as shown in 2-10. When arranged in this fashion, the coil takes on magnetic poles, just like a permanent magnet. Notice how the direction of magnetic flux always points to the north pole. If the direction of current flow were reversed, the coil's magnetic poles would also be reversed. To concentrate magnetic forces even further, a permeable core material can be inserted into the coil's center as in 2-11. Typically, iron, steel, and cobalt are considered to be the classical core materials, but iron-ceramic composite blends (sometimes called ferrite) are used as well. It is coils of wire such as these that form the foundation of all electromechanical devices.
Relays
A relay is simply a mechanical switch that is actuated with the electromagnetic force generated by an energized coil. A typical relay diagram is shown in 2-12. The switch (or contact set) might be normally open (N.O.) or normally closed (N.C.), while the coil is de-energized. When activated, the coil's magnetic field will cause normally open contacts to close, or normally closed contacts to open. Contacts are held in their actuated positions as long as the coil is energized. If the coil is turned off, contacts will return to their normally open or closed states. Keep in mind that a coil might drive more than one set of contacts.
Solenoid
The solenoid converts electromagnetic force directly into motion as illustrated in 2-13. Unlike ordinary electromagnets whose cores remain fiXed within a coil, a solenoid core is allowed to float back and forth without restriction. When energized, the magnetic field generated by a coil exerts a force on its core (called a plunger), which pushes it out from its rest position. If left unrestrained, a plunger would simply shoot out of its coil and fall away. Plungers are usually tethered by a spring or some other sort of mechanical return assembly. That way, a plunger will only extend to some known distance when the coil is flred, then automatically return to its rest position when the coil is off.
Motors
The motor is an absolutely essential part of every printer manufactured today. Motors operate the various transport systems that you will find. All motors convert electrical energy into rotating mechanical force. In turn, that force can be distributed with mechanical parts (e.g., gears and pulleys) to turn a platen or move a carriage. An induction motor performs this task by mounting a series of powerful electromagnets (coils) around a permanent magnet core, as shown in 2-14. The core (known as a rotor) is little more than a shaft that is free to rotate as its poles encounter electromagnetic forces. Each coil (also called a phase or phase winding) is built into the motor's stationary frame (or stator).
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