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Open Loop Speed Control of BLDC motor using Snetly

Open Loop Speed Control of BLDC motor using Snetly

Welcome to LMS Solution! In today's session, we will explore the concept of open-loop speed control for a Brushless DC (BLDC) motor using the Snetly modular real-time system.

Hardware Overview

The hardware unit of Snetly consists of interfacing digital input and output, an analog signal area, and an in-built gate drive circuit for digital outputs ranging from 0 to 15 volts. The demonstration involves connecting a three-phase BLDC motor, utilizing feedback from the motor's Hall signals for control.

Key Hardware Components:

  • Digital Input: Three Hall signals (HALL-A, HALL-B, HALL-C) with a 120-degree phase shift.

  • Current Sensor: Measures three-phase current of the BLDC motor.

  • Voltage Source Inverter: A two-level inverter directly connected to power semiconductor switches.

  • Power Supply: Utilizes a 24V DC supply for the 24V BLDC motor.

Model-Level Design

The model-level design is developed to run the motor in an open-loop speed control configuration. Since the BLDC motor is sensor-based, feedback from the Hall sensors is crucial. The model includes configurable lookup tables to generate gate signals for the voltage source inverter. A dead time controller is employed for each leg of the inverter.

Configuration Parameters:

  • PPR (Pulses Per Revolution): Configured as four for the motor.

  • Dead Time: Configured as one microsecond.

The model generates six gate signals for the six-step commutation (120-degree mode of operation). These signals are directly connected to the digital output pins with the in-built gate drive circuit.


  1. Hardware Connection: Connect the hardware unit as per the model-level design.

  2. Run Simulation: By varying the duty control, observe the motor starting to run.

  3. Observations:

    • Hall sensor feedback with a 120-degree phase shift.

    • Gate signals shown in the logic analyzer.

    • Current waveforms for each phase of the BLDC motor.

  4. Adjusting Motor Speed: Vary the duty control to observe changes in motor speed.

  5. Load Testing: Apply a load to the motor and observe the corresponding increase in current waveform.

  6. Motor Speed Control: Demonstrate speed control by adjusting the duty cycle.


The open-loop speed control of the BLDC motor using the Snetly modular real-time system provides a real-time, hardware-in-the-loop demonstration. The system's flexibility, ease of use, and direct integration with digital outputs make it a powerful tool for motor control applications.

For more information and in-depth insights, subscribe to the Snetly YouTube channel and LMS Solution. Visit for direct contact with application engineers and sales personnel at Snetly.

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