DC Motor Control Made of Solid State Switches

Figure 1 

The circuit illustrates the operation of solid state switches as it controls the movement and the direction of the motor as denoted by the LED.

• DC Motor – a single coil apparatus used to convert electric power into mechanical work by forcing current through the coil and producing a magnetic field that spins the motor; it consists of six basic parts namely the axle, rotor or armature, stator, commutator, field magnet, and brushes.
• TIP31 – a standard type of NPN bipolar junction transistor used for medium power linear switching applications
• Solid State Device – a device that is purely electronic with no moving parts and are generally faster, more reliable, and less expensive than their electromechanical counterparts

Using the TIP31A, semiconductor material provides the switching by reversing the bias of the switch when a zero or negative voltage is applied to the control electrode, it alters the direction of the motor as indicated by the LED. The first and second switches are normally open to create push button switches. If transistors are running underload, they will extract more current. The small built motor was controlled manually to permit precise amount of light in an area.

The diodes are physically positioned apart from each other and distributed in position among the transistors while each diode is positioned in a similar approach with an assembly of linked transistor for better flow of current between the diodes and the transistors. These diodes function as back electromotive force (EMF) which can be thought of as a regulator wherein it stops the motor from turning too quickly. The smaller the back EMF, the slower the motor will turn.

In designing a DC motor, some general notes should be taken into consideration such as audible noise, quality components, bearing choice, vibration, brush options, electromagnetic interference, motor commutation, quality components, coreles motors, lead wires and shielding, passive components, operating point, rotor inductance, drive profiles, environmental considerations, shaft loading, and quality and workmanship.

Under brushed DC motor applications were toys, car window lifters and electric antennas, servo drives, fans, cordless tools, transportation such as trains and trolley bus, electrical power steering & electro-hydraulic power steering, and automotive applications such as seat adjustment. Applications employing brushless DC motor were PC fans, ceiling fans, blowers, washing machines, industrial drive, electrical power steering, servo drives, electric vehicle traction drive, automotive applications, refrigerator, and air conditioning.

Source:www.zen22142.zen.co.uk/Circuits/Switching/dcmotor.html