Introduction: Dc Motor Speed Control Circuit

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In this short article, we are getting to find out how to form a DC motor speed negative feedback circuit. Mainly we are getting to find out how the circuit works and what's about the PWM signal? and the way the PWM signal is employed to regulate the DC motor speed.


DC motor may be a purely inductive Load so if you would like to regulate the speed of the DC motor then we've to upper / lower the voltage for higher / lower speeds. but in practically higher voltage and lower voltage isn't that sort of possible so, during this case, we use another sort of method which is named PWM better referred to as pulse width modulation.

What is PWM?
The word PWM is additionally referred to as Pulse Width Modulation. Suppose there's a voltage of 5 volts which is popping on and off in an interval. This on / off signal is especially presented as duty cycles now if there's a 50% duty cycle within the output voltage are going to be 50% of 5 volts so it'll be nearly 2.5 volts. The duty cycle are often 25% of fifty or 90% or maybe 100%. so now you'll calculate what the voltage is going to be when the duty cycle is going to be during a certain percentage. Now this PWM Pulses runs the transistor and it runs the Motor.

How does the Motor Speed negative feedback circuit work?
This is a really basic circuit that's made from 555 timer IC which can produce Square wave Pulses. There are numerous complimentary components for generating PWM pulses from the 555 timer IC. for changing the duty cycles of the PWM pulses we are employing a 100K potentiometer.

The Pin no 3 of the 555 timer IC provides PWM pulses these pulses aren't strong enough to run a DC motor. So what we'd like to try to do is to amplify the signal. For the amplification of the circuit, we've used N-channel MOSFET IRFZ44N.

The gate pin of the MOSFET is connected with the No 3 pin of the 555 timers through a resistor. When the MOSFET gets High PWM pulses then the duty cycle should be high so it means more current will be a due drain to source so, during this case, the motor will Speed Up within the fastest speed.

The same case happens when the PWM pulse is low. within the low duty cycles, the transistor is going to be switched in very low frequency. So, for this reason, the motor speed is going to be low during this case.


Step 1:

Here are Some Pictures for creating the Circuit. I even have made the DC Motor Speed Controller Circuit within the PCB for creating the circuit as simple as possible. you'll also make the circuit within the Breadboard. But there could also be loose connection So I even have Directly Soldered all Components. So, there'll not be any loose connection.

Step 2:

Step 3:

Step 4:

Step 5: Circuit Schematics:


Here I even have used IRFZ44N n channel MOSFET which is capable of high amperes. But you'll also use any sort of N-Channel MOSFETs. The ampere rating could also be very for other MOSFETs. 555 timer IC needs a continuing voltage so here I even have used 7805 IC for constant voltage from 7 to 35 volt.

you'll also use any voltage like 5 volts to fifteen volts for that 555 timer IC. I have connected a diode in parallel with the motor. this is often for the rear EMF Protection of the motor. this may not damage the MOSFET from Back EMF. this is often mandatory. You Can also read our another article: Click Here