There are several motor control circuits and this is one of the commonly used motor control circuit and it was done by employing a simple NE555 IC. The timer IC here was used to generate PWM waves so that the speed of the motor can be adjusted accordingly.PWM is nothing but Pulse Width modulation , a modulation technique in which the width of the output pulse was varied with respect to the amplitude of the input signal.Lets see how this DC motor speed control circuit works.
WORKING OF DC MOTOR SPEED CONTROL CIRCUIT:
The above IC 555 was wired as an Astable multivibrator which produces a series of square wave pulses as output.In order to make the IC 555 to produce PWM output signal modification in the astable circuit was needed.Generally the output frequency of the Astable multivibrator depends on the Resistors and Capacitors attached to it.The duty cycle of the output was governed by the Variable resistor R1 connected between the pin 6 and pin 7.This resistor holds the key for generating the PWM waves from the IC output so by varying the resistance in the R1 the output width of the pulse can be varied as desired resulting in the generation of PWM waves.
The next stage was very simple it helps in driving the DC motor.The output of the IC1 is coupled to the base of the transistor Q1 which drives the motor according to the incoming signal from the output of the 555 IC.When the duty cycle of the PWM signal is high then the speed of the motor will be high and vice versa.The V indicates the voltage required for the motor and it should be selected based on the motor you are about to control with the IC.The switch was used here inorder to change the direction of the running motor, when the voltage applied in the opposite direction of the motor it will result in running of the motor in opposite direction.Thus the R1 can be used as a switch in order to control the motor by this way the PWM generation and DC motor control can be done with simple 555 IC.
This low circuit is simple to implement and very efficient in working.This will be a great project to do for Electronics hobbyist and students.Share this post with others and post in your comments and queries about this post.
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