Copyright © A.F.Billington 2018. All rights reserved.


​​​​​​​​​​​​​Electromechanical components those which convert electrical energy into kinetic energy through movement. Typically they take advantage of electromagnetism to generate electromagnetic force.  An electromagnet is made through the coiling of copper wire around an iron core. When electrified the current flows around the coil of wire creating a magnetic field. The strength of the magnetic field is determined by the number of coils (windings) and amount of current

An Inductor is a common component that makes us of this effect. It is a passive two terminal component that can resist changes in current. As current passes through it it generates a magnetic field which can be used to store energy. Whilst the magnetic field is being created it resists any change in current. As the current is removed the energy is stored until the magnetic field breaks down. Consider it like a water wheel that picks up momentum slowly and continues to spin whilst slowing down. 


The simplest use of electromagnetism in an output is found in the Solenoid. When a current is applied to the solenoid the magnetic iron bar surrounded by coils of copper wire is repelled/attracted to the magnetic field. The movement of the bar using electricity can be incredibly quick and resist large amount of force. Once the current is removed a return spring relocates the bar to its resting position. Push (protrudes) or Pull (contracts) solenoids can be used depending on the application

Solenoids create a linear motion using an electromagnetic field making them an example of a transducer. They are used in the automotive industry to enable contacts for the starter motor when the ignition is on


In a DC motor electromagnetism is used to create rotational force. Permanent polarised magnets surround a wired electromagnet core attached to an armature which is electrically connected via brushes

  • As current is applied to the electromagnet in the centre it generates a magnetic field. It then becomes repelled/attracted to the permanent magnet North and South poles on the outside
  • This causes the armature to rotate. As it becomes aligned horizontally with the magnetic poles the torque becomes zero.
  • At this point the commutator switches the polarity of the current causing the armature to continue spinning, completing the turn. This is repeated to maintain rotational force from the momentum
  • Carbon brushes maintain a constant supply of current as the motor spins to the armature to maintain the electromagnetic field

Flemings 'left hand rule' can be used to determine the direction of motion in an electromagnetic motor. Using the thumb and first two index fingers as shown, you can work out the direction of motion based on the direction of the magnetic field (N > S) and current applied


Brushless DC motors (BLDC) are widely replacing standard brushed motors due to their higher efficiency, durability and reduced size. Unlike a brushed motor which has a permanent magnet on the outside, a smaller magnet is located on the central rotor.

  • Multiple copper coils are placed around the outside of the magnetic core. As current is applied to each paired coil individually they produce a electromagnetic field and repel/attract the central rotor magnet causing it to rotate
  • The electrical pulses sent to each of the coils is controlled by a microcontroller and can determine the speed and torque created
  • 'Hall Effect' sensors are placed in between the electromagnetic coils to detect the changing magnetic fields in order to control the current going to each coil, maintaining rotational movement

The removal of the brushes prevents sparking between the contacts which can occur in a DC motor causing cause damage that requires maintenanceshortening its lifespan. Equally, the size and weight can be reduced as well as the accuracy greatly increased through the use of microcontroller control. The two videos will explain both DC and BLDC motors in further detail


Stepper motors are widely used in CNC where specific positioning of the motor is required. As with brushless motors, electromagnetic coils are pulsed to produce movement. However, in the centre are two magnetic toothed gears and each coil around the outside has corresponding teeth. As the coils are electrically pulsed they attract/repel moving the gears along the tooth profile. They are therefore digitally controlled 

One gear has a magnetic North and the other a South. Each coil is energised with opposite polarity to attract one gear and repel the other. Typically around 200 rotational steps per revolution can be achieved at 1.8° of movement per step giving very precise control

Component Theory - Electromechanical