Intermittent Motor Stops with DRV8870DDAR : Fixing the Issue

Intermittent Motor Stops with DRV8870DDAR: Fixing the Issue

When working with motors controlled by the DRV8870DDAR motor driver, it can sometimes happen that the motor stops intermittently, causing performance issues. This article will provide a clear, step-by-step analysis of the problem, its possible causes, and effective solutions.

1. Understanding the Problem

The DRV8870DDAR is a popular H-bridge motor driver commonly used in motor control applications. An intermittent motor stop is when the motor ceases to run at random intervals and then resumes operation without any apparent reason. This can be frustrating, especially in critical applications like robotics or automation.

2. Possible Causes of Intermittent Motor Stops

There are several reasons why a motor may stop intermittently while using the DRV8870DDAR:

A. Power Supply Issues

Cause: The DRV8870DDAR requires a stable power supply to function properly. If there is a fluctuation in voltage or insufficient current, it can cause the motor to stop intermittently. This is especially common when the motor demands more current than the power supply can provide.

Solution: Ensure that your power supply meets the voltage and current requirements of both the motor and the DRV8870. Check the VM (motor voltage) and VCC (logic voltage) pins for appropriate voltage levels. If using a battery, make sure it is not running low on charge.

B. Overcurrent or Overload Protection

Cause: The DRV8870 features built-in overcurrent protection, which can cause the motor to stop if it detects excessive current draw due to a motor jam, overload, or short circuit.

Solution: Check the motor for mechanical issues such as binding, excessive load, or obstruction. Also, ensure the motor's current rating matches the limits of the DRV8870. If the motor is continuously drawing too much current, consider using a motor with a lower current rating or adding a current-limiting feature in your circuit.

C. Thermal Shutdown

Cause: The DRV8870 includes thermal protection, and if the device overheats due to excessive load or inadequate cooling, it may enter thermal shutdown mode, causing the motor to stop temporarily.

Solution: Make sure the DRV8870 is properly heat-sinked or has sufficient cooling. Ensure that the surrounding components have adequate airflow and are not generating too much heat. Monitor the temperature of the driver during operation to prevent overheating.

D. Faulty Wiring or Connections

Cause: Loose or poor connections in the circuit can lead to intermittent power delivery, causing the motor to stop unexpectedly.

Solution: Double-check all wiring connections, especially on the IN1, IN2, and VM pins of the DRV8870. Make sure that all connections are secure and well-soldered to avoid intermittent power loss.

E. Incorrect Control Signals

Cause: If the input control signals (such as PWM or logic signals) are unstable or incorrectly configured, the DRV8870 may misinterpret the commands, causing the motor to stop.

Solution: Review your control logic and ensure that the input signals to the IN1 and IN2 pins are consistent and correct. Ensure that the PWM signal (if used) is within the correct frequency range for the motor to operate smoothly. If using a microcontroller, check that the code is sending the correct signals in the proper order.

F. Driver Failure or Damage

Cause: While less common, the DRV8870 could be faulty or damaged due to static discharge, overvoltage, or physical damage, causing intermittent motor stops.

Solution: If all other potential causes have been ruled out, consider replacing the DRV8870 driver with a new one to eliminate the possibility of a defective component.

3. Step-by-Step Troubleshooting Guide

Here is a simple, step-by-step guide to troubleshoot and fix intermittent motor stops:

Step 1: Check the Power Supply Verify the voltage and current supplied to the DRV8870 and motor. Ensure that the power source can handle the motor's load. Replace or upgrade the power supply if necessary. Step 2: Inspect the Motor Check for any mechanical issues such as jams, excessive load, or damage to the motor. Test the motor without the driver to rule out any motor-related issues. Step 3: Monitor for Overcurrent or Thermal Shutdown Measure the current drawn by the motor during operation. Ensure that the driver is not overheating by measuring its temperature. Add a heat sink or improve cooling if necessary. Step 4: Check Wiring and Connections Inspect all wiring between the DRV8870 and the motor. Re-solder any loose connections and secure any potentially faulty wiring. Step 5: Verify Control Signals Ensure that the control inputs (PWM, IN1, IN2) are correct and stable. Use an oscilloscope or logic analyzer to check the integrity of the control signals. Step 6: Replace the Driver If all else fails, consider replacing the DRV8870 with a new one to rule out driver failure.

4. Preventative Measures

To prevent intermittent motor stops from occurring in the future, consider the following tips:

Always use a power supply that exceeds the motor's peak current demand. Ensure the DRV8870 has adequate cooling, especially when running motors under heavy load. Regularly inspect and maintain the motor for mechanical issues. Implement a robust error-handling system in your code to manage motor control signals and detect faults early.

Conclusion

Intermittent motor stops with the DRV8870DDAR can be caused by a range of factors, including power supply issues, overcurrent protection, thermal shutdown, wiring problems, or faulty control signals. By following a systematic troubleshooting approach, you can identify and resolve the root cause of the issue and restore reliable motor operation. Always ensure that all components are properly rated for your motor's specifications to prevent future issues.