How to Select a Motor Driver
Motor drivers are an integral part of robotics systems. They supply the high currents and voltages required to spin brushed or brushless DC motors.
They take low-power control signals from a microcontroller and convert them into H-bridge power transistor switching patterns that direct current flow in specific directions and speeds. Choosing the right driver is critical for system performance.
Voltage and Current Ratings
Motors are a key component in industrial machinery, transforming electrical energy into mechanical power to control conveyor systems and robotic arms. When selecting a motor driver, it is important to consider its voltage and current ratings, as well as its logic level and features. A correctly selected driver ensures that the microcontroller and motor operate at the correct speed and power, and prevents damage from too much current or high voltage.
The peak and DC or RMS maximum currents of a motor driver are determined by the thermal limits and overcurrent protection (OCP) circuitry. The IC data sheet usually includes an estimation of the maximum current that can motor driver be delivered by the device at 25°C ambient temperature, on a standard JEDEC-spec PCB construction and using the best possible thermal paths.
When the motor driver IC is turned on, the current from the supply voltage will first flow to the positive terminal via one pair of transistors and then to the negative terminal via the other pair of transistors. This alternate flow of current forms an H-bridge circuit.
The power dissipated by the motor driver IC causes the junction-to-ambient temperature, referred to as thJA in the data sheets, to rise. If thJA exceeds a certain threshold, the integrated circuit’s OCP circuitry disables its outputs to protect the device. The thJA estimate can help designers optimize the thermal aspects of the motor driver IC design, such as choosing a suitable heat sink and ensuring adequate cooling using PCB design techniques like continuous top-layer copper pours and direct-connect thermal vias.
Control Inputs
The motor driver contains power transistors (MOSFETs or BJTs) and control circuitry. The control circuitry often includes current sensing and over-temperature shutdown mechanisms. It’s important that the MOSFETs are not exposed to excessive voltage, which can damage or destroy them. A transient voltage protection circuit should be included.
Most of the inputs of a motor driver are PWM inputs, which can be used to control the speed or direction of the motor. Depending on the type of motor, it may also require an armature current or field current input.
For example, a motor driver based on the L298N dual H-bridge motor driver IC has two control input pins called IN1 and IN2. Applying a low-level PWM signal to IN1 while holding IN2 low causes the motor to spin in one direction. Reversing the direction is as simple as switching the state of IN1.
In addition to PWM inputs, many motor drivers support digital and analog inputs. These inputs are usually read out in milliseconds and processed in an internal sequence program of the controller to determine motor position or speed. For example, Nanotec motors with integrated controllers can accept digital and analog inputs that are used to trigger the motor movement. Some motor drivers have DIP switches, configuration files or software that enable the user to select which input method is required.
Protection Features
Motor drivers are essential to industrial automation systems, controlling a variety of motors including those used in conveyor belts and robots. They control the speed, direction, and torque of motors by motor driver wholesale amplifying input signals from a microcontroller or other host controller. They also provide built-in protection against things like over-current and over-temperature, making them a critical link between digital commands and real-world actuation.
Most modern driver ICs integrate both amplifier and motor driver functions into one compact package for space efficiency. They use sophisticated techniques like gallium nitride transistors to deliver high-speed switching and fast response times. Additionally, many feature integrated sensors to monitor conditions and regenerative braking capabilities for energy conservation.
In addition to these standard features, advanced motor drivers are able to detect a variety of fault conditions and shut down when needed. They often include a fail-safe mechanism that disconnects power to the motor coils, called a thermal overload. This protects the motor from damage from a sudden loss of current that can occur in the event of an electrical fault downstream in the power wires or within the motor itself.
To prevent thermal overload, designers should pay close attention to the thermal specifications of the driver. They can minimize this risk by designing the circuit board using best practices for dissipating heat, such as through top-layer pours and copper traces that are as wide as possible to improve heat conduction. They should also employ proper grounding and shielding to avoid electromagnetic interference (EMI).
Reliability
Motor drivers are essential for robotics and automation projects as they provide the voltage, current, directionality, and protection required to efficiently operate your robotic devices. Often in the form of integrated circuits (ICs), they feature power transistor configurations like H-bridges that control the current and polarity of motor coils, as well as a number of other important features and capabilities that help enhance your system performance.
Unlike a microcontroller, a motor driver can handle much higher currents and provides built-in protection against things like over-current and over-temperature. They also offer space efficiency by integrating the amplifier and motor driver functionalities into a single device, making them a cost-effective and user-friendly solution for your robots, automation machines, and electric vehicles.
The reliability of a motor driver is an important consideration, particularly when operating your devices in industrial applications. They play a critical role in controlling the speed and direction of your motors by translating low-voltage signals from your microcontroller into the high current needed to activate the motors. As such, you need to make sure your motor driver has the appropriate voltage and current ratings for your application, as using a device that isn’t sufficiently rated can cause it to overheat or damage your motors. To further increase operational precision, many modern motor drivers include sensors that detect stall conditions and active braking capabilities.