DC motor speed control

In this article , It is explained how can DC motor speed control can be varied by two methods.

Controlling the speed of DC motors at many applications becomes so important that, without speed control at those situations , the complete project gets damaged.

What is a DC motor:

As the name is suggesting that this form of motors are operated by DC source of energy. These motors are widely used in the field of robotics .These motors are available in different types based on their speed( in RPM) and based on torque of the motor. Basically High torque motors have less rotational speed.

In this RE tutorial we will be manually controlling speed of a DC motor by two methods:

               1. Voltage control method

               2. Current control method

1. Voltage control Method

               In this method of speed control, voltage across the motor will be varied using a potentiometer.
The circuit requires for this is method is provided below.

How Voltage is Varied:
A potentiometer is connected in series with the motor, so when the value of potentiometer increases , the voltage drop across potentiometer increases, which results in decrease in the voltage across the motor.

Case 1:

When potentiometer is at minimum reading, then almost complete voltage is supplied to motor, which results in maximum speed of a DC motor.
In this case speed is 17,382 RPM

 Case 2:

When the potentiometer has set to a value, then some voltage is dropped across the potentiometer and which results in less supply of voltage to the motor, so in this way little bit speed is decreased.
Here in this case speed is about 2782 RPM

2. Current control method

In this method, the current through the motor is varied . In this method also we will be using Potentiometer to vary the speed. But there is small difference here, in the previous when the potentiometer reading was minimum then, speed of the motor was maximum, but in this case it is quite opposite. When the Potentiometer holds maximum value, then the motor will be running at its maximum speed.

CASE 1:

When potentiometer has maximum reading, then there will be a high resistance component parallel to DC motor, which makes current to avoid high resistance path and it would prefer low resistance path, So larger amount of current will be passing through DC motor.
In the case below, Ammeter has a reading of 140mA and it is shown that potentiometer has maximum value it can hold and it results in very high speed.

CASE 2:

When potentiometer has minimum reading, then there will be a low resistance component parallel to DC motor, which makes current to avoid high resistance path and it would prefer low resistance path, So larger amount of current will be passing through Potentiometer and very less amount of current would pass through DC motor.
In the case below, Ammeter has a reading of 35.8 mA and it is shown that potentiometer has minimum value it can hold and it results in very low speed.

We are hoping that you would have understand the article and have learnt a lot new things. If you are having any doubt regarding the article, let us know in the comments.