HBridgeMotor

Generic h-bridge motor controller driver.

Info

An h-bridge motor controller enables a control signal to drive a much larger load in either polarity, allowing the Netduino to drive DC motors in forward or reverse from an external power supply. Using pulse-width-modulation (PWM) as the control signal, provides not just forward or reverse control, but variable speeds in either direction.

Sourcing

This generic driver works with standard h-bridges ICs such as the Texas Instruments L2N93E or SN754410 chips.

It should also work with heavier duty L298N drivers.

Example

The following example uses a dual h-bridge chip to control two motors. Both the L293NE and NS754410 are dual h-bridge chips that can drive two motors in both forward and reverse. This is a common configuration for wheeled robots. Forward and reverse motion is obtained by setting both the motors to have the same forward or reverse speed, and turning is accomplished by setting them to different speeds.

Sample Circuit

Though h-bridge motor controllers come in various form factors, they typically share the following pins and usages:

Motor Controller Pin Description
1,2EN or ENABLE A Motor 1 enable. This should be configured as enablePin in the constructor, and it controls whether or not the motor is powered. The HBridgeMotor driver will automatically set this to high (enabled) when the speed is not zero. This is also enabled when IsNeutral is set to false, as powering the motor will cause it to brake when the speed is set to 0.

On the L2N93E and SN754410 chips, this is labeled as 1,2EN, and on the L298N, it’s typically labeled as ENABLE A.
3,4EN or ENABLE B Motor 2 enable pin. If you are driving two motors, you’ll need two HBridgeMotor objects, as shown in the example below.
[1,2]A or INPUT [1,2] Motor 1 control inputs. These are configured as the a1Pin and a2pin constructor parameter. These are the low-voltage control signals for motor 1 forward and reverse.

On the L2N93E and SN754410 chips, this is labeled as 1A and 2A, and on the L298N chip, it’s typically labeled as INPUT 1 and INPUT 2.
[3,4]A or INPUT [3,4] Motor 2 control inputs.
GROUND or GND Common/ground. Both the motor power supply and the logic power supply should be tied together on the same common ground plane.
VCC2, +12V, or Vs This is the positive voltage supply that drives the motors. Depending on the chip used, this may be anywhere from 4.5V up to 50V.
VCC1, +5V, or VSS This is the logic voltage supply that powers the chip logic. This should be tied into the 5V voltage pin on the netduino.

The following breadboard diagram illustrates connecting two motors to an h-bridge chip that uses a external power supply to drive the motors:

Code

The following code creates an h-bridge controller with the PWM controllers on pins 3 and 5, and the enable pin on pin 4. It then sets the motor speed to 100% forward, stops the motor for half a second, and then sets the motor speed to 100% reverse.

using System.Threading;
using H = Microsoft.SPOT.Hardware;
using N = SecretLabs.NETMF.Hardware.Netduino;
using Netduino.Foundation.Motors;

namespace HBridgeMotor_Sample
{
    public class Program
    {
        public static void Main()
        {
            var motor1 = new HBridgeMotor(N.PWMChannels.PWM_PIN_D3, N.PWMChannels.PWM_PIN_D5, N.Pins.GPIO_PIN_D4);
            var motor2 = new HBridgeMotor(N.PWMChannels.PWM_PIN_D6, N.PWMChannels.PWM_PIN_D10, N.Pins.GPIO_PIN_D7);

            while (true)
            {
                // set the speed on both motors to 100% forward
                motor1.Speed = 1f;
                motor2.Speed = 1f;
                Thread.Sleep(1000);
                motor1.Speed = 0f;
                motor2.Speed = 0f;
                Thread.Sleep(500);
                // 100% reverse
                motor1.Speed = -1f;
                motor2.Speed = -1f;
                Thread.Sleep(1000);
            }
        }
    }
}

API

Properties

float IsNeutral { get; set; }

Whether or not the motor connected to the h-bridge is not enabled. If IsNeutral is true, then the motor controller is disabled and rotor spins freely. If IsNeutral is false, then the motor will be energized and the rotor will be “locked” into position.

public float MotorCalibrationMultiplier { get; set; } = 1;

float Speed { get; set; }

The speed, represented by a value from -1 to 1 of the motor. -1 means 100% reverse, and 1 means 100% forward.

Constructors

public HBridgeMotor(H.Cpu.PWMChannel a1Pin, H.Cpu.PWMChannel a2Pin, H.Cpu.Pin enablePin)

Instantiates a new HBridgeMotor on the specified pins.

Parameters
  • a1Pin - The PWM channel pin that creates the forward rotation signal.
  • a2Pin - The PWM channel pin that creates the reverse rotation signal.
  • enablePin - A digital IO pin that enables and disables the h-bridge, which controls IsNeutral.