The Tool Desk
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How an H-bridge reverses a motor
Picture the motor between two sides of a bridge, with a high-side and low-side switch in each side. Turning on opposite diagonal switches sends current through the motor in one direction. Switching to the other diagonal reverses current and therefore the motor’s applied polarity. This is the basic way an H-bridge motor driver makes a brushed DC motor run forward or reverse. Texas Instruments’ H-bridge application note and the DRV8411 datasheet document these drive states.
How PWM controls speed and current
PWM rapidly switches the bridge between drive and off states. Changing the fraction of each cycle spent driving—its duty cycle—changes the applied motor drive and can regulate current. The motor is inductive, however, so its current continues during switching intervals rather than disappearing when drive is removed. The chosen off-state determines where that current flows and how quickly it decays. TI’s DRV8411 datasheet describes slow-decay recirculation and high-impedance coast states as well as forward and reverse drive.
Brake and coast are different states
In a slow-decay or braking state, the bridge provides a path for current to recirculate through the motor and switches; this slows current decay. In high-impedance coast, the outputs are left undriven, allowing the motor to coast. These states are not interchangeable: the selected behavior affects motor response during PWM off time and when drive is disabled.
Prevent shoot-through when switching
Never command both switches in the same bridge leg to conduct at once. That creates a direct path from the supply to ground, called shoot-through, which can damage the switches or driver. When changing between complementary switches, the outgoing device must turn off before the incoming one turns on. The gap is called dead time or dead-band.
Integrated drivers may insert dead time automatically. TI states in the DRV8411 datasheet that it inserts dead time when an output changes between driving high and driving low to prevent shoot-through. With discrete MOSFETs, the designer must account for gate-driver timing and differences between turn-off and turn-on times. Microchip notes that dead-band is especially relevant when bridge direction changes near 100% duty cycle or when a power switch and its driver turn off more slowly than they turn on; see its full-bridge dead-band guidance.
Rank #2
- L298N Motor Driver Controller Board Module: L298N as main chip. Can drive one 2-phase stepper motor, one 4-phase stepper motor or two DC motors
- Operating mode: H-bridge driver (dual)
- Logic voltage: 5V(current 0mA-36mA)
- Drive voltage: 5V-35V(current: 2A (MAX single bridge)
- Maximum power: 25W
Choose a driver for the motor and robot
A brushed DC motor driver module or IC implementing an H-bridge can simplify bidirectional motor control, but the circuit name alone is not enough to select one. Check the motor’s supply-voltage requirements and current demand, including startup and stall conditions, then confirm that the driver can handle those demands under the robot’s actual thermal conditions.
- Voltage and current: Match the driver’s operating range and continuous and peak current capability to the motor and power source. Startup and stall current can exceed normal running current.
- Current control and measurement: Check whether the driver offers current limiting, regulation, or sensing if the application needs torque control or overload awareness.
- Control interface: Verify how the driver accepts direction and PWM commands and whether that interface suits the robot’s controller.
- Switching architecture: Determine whether the device integrates power MOSFETs or drives external ones, and how it handles dead time.
- Protection and heat: Review supported fault protections and thermal limits, and ensure the board or system can dissipate the heat generated in use.
For example, TI’s DRV8411 is a dual H-bridge IC, while the DRV8702-Q1 documentation illustrates a gate-driver architecture using external MOSFETs. These are examples of different design approaches, not universal matches for every robot motor.
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Quick Recap
Best Value
- DROK DC motor driver input voltage range is DC 6.5V-27V, can be input DC 12V or 24V, rated output current of each port is 7A, total output power is 160W.
- STRONG DRIVE: the motor controller board adopts dual H bridge, can drive two DC motors at the same time.
- FORWARD and REVSERSELY ROTATE: the IN1, IN2/IN3, IN4 port can control forward or reverse motor rotation.
- PWM SPEED CONTROL: enable signal terminal (ENA) input PWM can regulate speed, PWM frequency range 0-10KHZ.
- UNDER VOLTAGE PROTECTION: the motor driver module is with under voltage protection to prevent instantaneous large current from damaging the module.
Rank #4
- DROK DC motor driver input voltage range is DC 6.5V-27V, can be input DC 12V or 24V, rated output current of each port is 7A, total output power is 160W.
- STRONG DRIVE: the motor controller board adopts dual H bridge, can drive two DC motors at the same time.
- FORWARD and REVSERSELY ROTATE: the IN1, IN2/IN3, IN4 port can control forward or reverse motor rotation.
- PWM SPEED CONTROL: enable signal terminal (ENA) input PWM can regulate speed, PWM frequency range 0-10KHZ.
- UNDER VOLTAGE PROTECTION: the motor driver module is with under voltage protection to prevent instantaneous large current from damaging the module.
Rank #3
- Massive 50A High Current Drive & H-Bridge Design: Engineered for high-power tasks, this motor driver module utilizes a full H-bridge MOSFET circuit with extremely low internal resistance. It reliably drives heavy loads up to 50A, making it ideal for large DC motors in industrial equipment and automation.
- Bidirectional Motor Control with High-Frequency PWM: Achieve precise forward and reverse rotation effortlessly. This motor controller accepts PWM signals up to 200kHz, allowing for smooth speed regulation and instant direction changes.
- Dedicated PWM Isolation for Microcontroller Safety: Protect your sensitive control board with built-in signal isolation. Unlike basic drivers, this module features an isolation chip that separates the high-current motor drive from your microcontroller's logic level.
- Wide Logic & Power Voltage Compatibility: Designed for versatility, it accepts a wide power supply range from 5V to 15V. The logic input is fully compatible with 3.3V and 5V microcontrollers, as well as up to 12V control signals.
- Compact & Efficient High-Power Solution: Packing immense power into a small footprint (1.7"x1.9"), this module saves valuable space in your project enclosure.
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