DC Motor speed control Circuit using IC 555

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dc-motor-speed-control-circuit-diagramThere 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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Frank Donald

Junior Network Engineer at Tata Communications
Frank Donald is an Electronics and Communication Engineer who is very passionate about his subject. Reading, Surfing and Blogging are the things he loves.

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23 Comments on "DC Motor speed control Circuit using IC 555"

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Sg
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Is it necessary to use D1 D2?

zain channar
Guest

I MADE THIS CIRCUIT AND IT WORKED PERFECTLY but at first i didnot understand how to connect motor then i just connect two 9v battery , one to power the ic and the other for motor ( 3v)
the technique is to connect the +ve of 2nd battery to vm and the -ve to pin 1 of ic or -ve of 1st battery

Jenn
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Hey, can you explain what is the function of c1 and c2

prakhar
Guest

Hi, can you please explain what is the function of transistor Q1?

prakhar
Guest

What is the function of transistor Q1?

aslı
Guest

Hi, can I use relay instead of DPDT switch.(I dont have DPDT switch) and can I use 2 source in circuit
Thank you

Bernice Lee
Guest

Hi, i m not really understand abt the way to connect the voltage to the motor, where is the return path of this voltage? Can u pls explain to me? tq very much

ashraf shah
Guest

what is the function of 3 diodes in this circuit. plz explain each??

eduard
Guest

Hi,
I build your speed controller using the 555 ic and it works but the 33 ohm resistance gets very hot, is that ok ?.
And I conected a jumper from the 12v power suply to the negative to the motor, its that ok ? there is another way to conect the power to the motor ?
Thank you very much, I wait for your advice.

Frank Donald
Guest
Hello Eduard, The current rating of the motor is very crucial normally the motor consumes slightly higher current than the rated current. And this might be the reason for your problem not for sure. So i suggest you to pick a transistor with higher current rating and substitute in the circuit instead of BD139 or you could go for motor Driving IC’s such as L293D. Here is a circuit which might help you with this Motor control using L293D. Answering your 2nd question, motors doesn’t have fixed terminals i.e positive and negative. For a DC motor to work you must… Read more »
Chuado
Guest

If i want to use the L293D in this circuit where should i put the GND pin of this? at the GND or at the colector of the BD?

hitler
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saatana paskakytkentä homo!!!!!!!

Frank Donald
Guest

Sorry Couldn’t get you, Kindly use English.

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