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What is a Motor Control PCB, and How Does It Work?

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PCB makers design circuit boards to operate specific devices or systems. The motor control PCB, for instance, runs an electric motor, ensuring its proper working, efficiency, and safety. These functions make it a critical part of electrical equipment and systems. Below, we look deeper into this PCB type and its application in different industries.

What is a Motor Control Board?

It’s a printed circuit board used to operate an electric motor. You can also call it a motor driver PCB since it regulates the power going to its windings, causing it to either start spinning or stop.

The board also contains the electronics and circuitry to adjust speed and torque. Other functions include power management for efficiency and safety features like overload protection and thermal shutdown.

The board is available in different types and sizes. It can be a simple module for a small DC motor or a complex board for the three-phase motor of an industrial system or unit.

Some driver PCBs connect to separate controllers and receive drive inputs. Some incorporate the microcontroller in their circuits, providing control and drive functions.

A control PCB for a lathe machine
A control PCB for a lathe machine
Resource: https://www.youtube.com/watch?v=VqDopj8-BBA

Motor Control PCB Function

A motor PCB ensures its proper working. It receives user inputs or sensor information, interpreting the signals to determine the required operation. Using the inputs, it performs the following functions:

Motor Starting and Stop

The primary function of the motor circuit board is to start and stop its rotation. The PCB opens the power circuit to connect it to a voltage source for the start function.

The board also contains the electronics that disconnect the power source to stop the motor and a circuit that applies a reverse braking voltage or braking resistance.

Jogging and Inching

Jogging and inching are everyday motor operations. In jogging, the PCB applies full line voltage momentarily, starting and stopping the motor to produce short thrusts of motion. These motions then move a load.

Inching starts the rotation in short bursts but at a lower voltage. These operations are helpful when setting machine tools or using applications that require precise load positioning.

Communication and Feedback

Motor control circuits for advanced systems feature communication interfaces to connect them to other devices or systems. Some incorporate sensors and other devices to operate closed-loop, especially when designed for intelligent systems.

Motor and Circuit Protection

The board contains over-temperature and overload detection circuits. These protect the board and other circuits against electrical faults and overheating.

However, the protection continues beyond the board level. It also includes external safety devices like relays and circuit breakers for overload and short-circuit protection.

H-bridge motor driver circuit boards
H-bridge motor driver circuit boards
Resource: https://www.youtube.com/watch?4cxWFa4kg_o

Motor PCB Control Methods

The motor driver is the part that directly controls the power going to the stator or armature coils. It typically contains discrete components to handle the higher current and operates using the controller inputs. The typical control PCB uses these types of driver circuits.

H Bridge Control

The schematics of an H-bridge circuit form an “H.” It consists of four switches grouped in two and comprises bipolar transistors or, most often, MOSFETs.

Closing two of these switches applies power in one direction. Closing the other two switches changes the polarity and direction of rotation. The H Bridge driver is the most used control method for DC motors.

Variable resistance Control

In this method, the driver PCB controls the amount of current flowing in the armature coils using resistors. By varying the resistance, it adjusts voltage, thereby regulating speed and torque.

In addition to speed control, the resistors help limit inrush currents. It has the advantage of running, ensuring safe voltage levels, and preventing overheating.

PWM Control

PWM means Pulse Width Modulation. It refers to a control method where the driver circuit rapidly switches the power on and off, producing a series of square wave pulses.


Varying the on/off speed (frequency) changes the width of the pulses. That, in turn, varies the voltage, allowing the PCB to adjust speed without reducing the current and losing torque.

Stepper motor control board design and layout
Stepper motor control board design and layout
Resource: https://www.researchgate.net

Types of Motor Control Circuit Boards

Different types of motors use various types of control circuit boards. Based on this classification method, we have the following types: AC, DC, stepper, and servo motor PCBs.

AC Motor Control PCB

You can also call it a variable-speed driver or AC inverter. It works by changing the power frequency to control functions like speed and torque. The AC driver suits uses that require a constant variation of speed.

DC Motor Control PCB

The DC type changes AC input into a pulsed, one-way current. It’s typically employed in DC motors running on AC power. The DC board is popular in low-speed applications.

Stepper Motor Control PCB

This driver type converts input power to a pulsed DC output, feeding it to the stator phases and causing them to turn in “steps.” This control method eliminates the need for a feedback system. Increasing the speed of pulses increases the speed of rotation and vice versa.

Servo Motor Control PCB

A servo motor controller PCB uses a variable resistor (potentiometer) and PWM signal for position, speed, or torque regulation. Digital versions use a microprocessor instead. A closed-loop mechanism with a sensor enables the controller and driver circuits to ensure correct positioning.

A scooter's motor control circuit board
A scooter’s motor control circuit board
Resource: https://www.youtube.com/watch?tbB3edRw4o4

Motor Control PCB Applications

The electric motor board is standard in many applications, from home appliances to the advanced automation systems found in manufacturing facilities. Below is a list of applications that require this circuit board type.

Consumer Electronics

These PCBs are integral to consumer electronics like fans, washing machines, air conditioners, etc. The boards regulate their operation and interface with various device inputs to provide advanced control options.

Manufacturing Equipment and Systems

The board runs motorized systems like conveyors, CNC machines, and sorting or packaging equipment in the manufacturing industry. It regulates varied functions like rotation, load holding, and actuation.

Automotive Systems

Different automotive systems use dedicated PCBs to regulate the working of various components crucial to the proper operation of vehicles. These include air conditioning, windshield wipers, multiple pumps, and window opening and closing systems.

Robotics

Electric robotic systems rely on the control circuit boards to move arms, grippers, and other parts. These robotic systems find practical applications in industrial automation, medical devices and equipment, and other industries.

Electric Vehicles

Electric cars, scooters, and other E-vehicles rely on the PCB-controlled electronic for precise rotation and other functions. The circuit boards connect to other devices, including sensors, to regulate propulsion and braking.

Military Equipment and Defense Systems

Motorized military devices and defense systems contain unique controller and driver circuit boards that start, stop, and vary the speed to achieve desired functions. Electronic control makes the systems highly accurate, with other benefits like energy efficiency.

Aerospace Systems

Electric motors move aircraft flaps, landing gear, and other components. All these systems require PCBs to receive inputs and regulate power, ensuring precise movements. The boards must operate reliably and withstand harsh environments.

Conclusion

The motor control PCB is a critical part of devices or systems that use electric motors, from home appliances to the immense machinery of manufacturing plants. It has a unique circuit that can regulate operation, allowing varying speeds and other benefits such as overload and over-temperature protection.

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