Dec 16, 2019

Stepper Motor Basics: Working Principle, Type, Application

A stepper motor is a mechanical device it converts electric power into mechanical power. Also, it's a brushless, synchronous motor which will divide a full rotation into an expansive variety of steps. The motor’s position is often controlled accurately with a none feedback mechanism. Stepper motors are like switched reluctance motors.

The stepper motor uses the speculation of operation for magnets to create the motor shaft flip an exact distance once a pulse of electricity is provided. The stator coil has eight poles, and therefore the rotor has six poles. The rotor would force twenty-four pulses of electricity to maneuver the twenty-four steps to create one complete revolution. differently, to mention this is often that the rotor can move exactly 15° for every pulse of electricity that the motor receives.

Stepper motor may be a brushless DC motor that rotates in steps are very helpful as a result of it can be exactly positioned with none feedback sensing element, which represents an open-loop controller. The stepper motor consists of a rotor that's typically a static magnet and it's enclosed by the windings of the stator coil. As we tend to activate the windings step by step during a specific order and let a current flow through them they'll magnetize the stator coil and build magnetism poles severally that may cause propulsion to the motor. thus that’ the essential working rule of the stepper motors.

Types of Stepper Motor:

There are three types of stepper motors

  1. Permanent magnet stepper
  2. Hybrid synchronous stepper
  3. Variable reluctance stepper 

Permanent Magnet Stepper Motor: permanent magnet motors use a static magnet within the rotor and operate the attraction or repulsion between the rotor magnet and also the stator coil electromagnets.

Variable Reluctance Stepper Motor: Variable reluctance motors have an obvious iron rotor and operate supported the principle that minimum reluctance happens with minimum gap, thus the rotor points are attracted toward the mechanical device magnet poles.

Hybrid Synchronous Stepper Motor: Hybrid stepper motors are named as a result of they use a mix of the static magnet and variable reluctance (VR) techniques to realize the most power in little package size.

Operation of Stepper Motor:

Stepper motors operate otherwise from DC brush motors, that rotate once the voltage is applied to their terminals. Stepper motors, on the opposite hand, effectively have multiple toothed electromagnets organized around a central gear-shaped piece of iron. The electromagnets are energized by an external negative feedback circuit, as an example, a microcontroller.
To make the motor shaft flip, 1st one magnet is given power, which makes the gear’s teeth magnetically interested in the electromagnet’s teeth. the purpose once the gear’s teeth area unit is so aligned to the primary magnet, they're slightly offset from the successive magnet. thus once a successive magnet is turned ON and therefore the 1st is turned OFF, the gear rotates slightly to align with successive one and from there the method is perennial. every one of these slight rotations is named a step, with a whole number of steps creating a full rotation. therein means, the motor is turned by an exact. Stepper motor doesn’t rotate ceaselessly, they rotate in steps. There are four coils with a 90o angle between one another fixed on the stator coil. The stepper motor connections are determined by the method the coils are interconnected. during a stepper motor, the coils aren't connected.

 The motor contains a 90o rotation step with the coils being energized during a cyclic order, decisive the shaft rotation direction. The operating of this motor is shown by operative the switch. The coils are activated asynchronously in 1-sec intervals. The shaft rotates 90o whenever consecutive coil is activated. Its low-speed force can vary directly with current.

The output of the timer is employed as a clock for 2 7474 twins ‘D’ flip-flops (U4 and U3) designed as a hoop counter. once power is at the start switched on, solely the primary flip-flop is ready (i.e. q output at pin five of U3 are at logic ‘1’) and therefore the alternative 3 flip-flops are reset (i.e. the output of q is at logic 0). On receipt of a clock pulse, the logic ‘1’ output of the primary flip-flop gets shifted to the second flip-flop (pin nine of U3). so logic one output keeps shifting circularly with each clock pulse. q outputs of all the four flip-flops are amplified by Darling-ton semiconductor arrays within ULN2003 (U2) and connected to the stepper motor windings orange, brown, yellow, black to sixteen, 15,14, thirteen of ULN2003 and therefore the red to +ve provide.

Advantages of Stepper Motor:

  1. The rotation angle of the motor is proportional to the input pulse.
  2. The motor has full force at standstill.
  3. Precise positioning and repeatability of movement since sensible stepper motors have an accuracy of three – five-hitter of a step and this error is additive from one step to follow.
  4. Excellent response to the beginning, stopping and reversing.
  5. Very reliable since there aren't any contact brushes within the motor. so the lifetime of the motor is solely dependent on the lifetime of the bearing.
  6. The motor's response to digital input pulses provides open-loop management, creating the motorless complicated and fewer expensive to manage.
  7. It is the potential to realize terribly low-speed synchronous rotation with a load that's directly coupled to the shaft.
  8. A wide vary of motion speeds will be complete because the speed is proportional to the frequency of the input pulses.


  1. Industrial Machines – Stepper motors area unit employed in automotive gauges and machine tooling machine-controlled production instrumentation.
  2. Security – new police investigation product for the safety trade.
  3. Medical – Stepper motors area unit used within medical scanners, samplers, and additionally found within digital dental photography, fluid pumps, respirators, and blood analysis machinery.
  4. Consumer physics – Stepper motors in cameras for automatic photographic camera focus and zoom functions.

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