DC Motor Control Using H Bridge

This article clarifies how one can alter the course and speed of little DC motor utilizing exceptionally basic circuit manufactured utilizing promptly and effortlessly accessible convenient parts. In the first place we will perceive how we can alter the course of motor and after ward we will perceive how we can fluctuate the pace of DC motor. At that point I will clarify exceptionally basic DC motor controller circuit that alters course and additionally fluctuates the velocity of DC motor. So let us begin. 

Let me know how to alter course of turn of DC motor? 

It is exceptionally straightforward. The greater part of smaller than usual DC motors have two terminals since they are arrangement sort (armature and field windings are associated in arrangement) DC motors. If it's not too much trouble allude the figure given underneath. 



As appeared in figure there are two terminals "An" and "B" of DC motor. Presently on the off chance that we associate terminal A with +Ve supply and terminal B with –Ve supply or ground the present will spill out of motor from A to B and motor will rotate in one direction – say clockwise (CW) or forward bearing. Presently as appeared in second figure we change the supply terminals. Presently B is associated with +Ve and An is associated with ground. The present will spill out of motor from B to An and motor will turn in other bearing (counter clockwise – CCW or opposite). 

So next inquiry is how to give reversible supply to motor? 

The course of action is appeared in right half of figure. Four switches are associated in the middle of +Ve supply and ground and servo motor is associated in the middle of two switches as appeared. Such circuit course of action is known as H-scaffold since it would seem that letter "H" (H-span circuits are most broadly utilized as a part of DC motor drivers). Give us a chance to perceive how it gives reverse supply to motor. 

In the event that SW1 and SW4 are squeezed all the while then current will spill out of +Ve – SW1 – A – B – SW4 – Gnd. So motor will turn in one bearing. Open (discharge) SW1 and SW4 to stop motor. Presently if SW2 and SW3 are squeezed current will spill out of +Ve – SW2 – B – A – SW3 – Gnd. So motor gets reverse supply and it will rotate in another direction. 

(Alert: care must be taken that SW1 and SW3 or SW2 and SW4 must not be squeezed at the same time else it will cut off supply) 


The circuit replaces the switches with NPN sort transistors. We as a whole realize that transistor fills in as switch. For NPN transistor on the off chance that we give +Ve information to construct it will turn With respect to and on the off chance that we give 0 data it will be killed. 

So in this circuit if Q1 and Q4 are turned ON all the while the motor will pivot forward and if Q2 and Q3 are turned ON then motor will turn reverse. 

Is it true that it isn't exceptionally straightforward? 

Motor can be pivoted forward and turn around utilizing 4 transistors as it were. 

Presently let us move to change the pace of DC motor. The DC motor speed fluctuates as connected data voltage changes. As you increment connected info voltage the rate will increment and the other way around. Applying max evaluated voltage will turn servo motor at full speed (alert: don't make a difference more than max appraised voltage to motor generally motor windings may get blazed). 

Presently the inquiry is how to apply variable voltage to motor? 

One of the extremely well known techniques for producing variable DC voltage is heartbeat width regulation (PWM). It is clarified in figure given underneath. 


Beat width adjustment implies fluctuating the width (obligation) of heartbeat. Width implies ON time Ton of heartbeat. The normal output voltage (Vdc or Vavg) is given by mathematical statement 

Vdc = [Ton / (Ton+Toff)] × Vs

It straightforwardly relies on Ton. As appeared in above assume if obligation is half the normal output voltage Vdc is precisely the half of Vs. In the event that obligation is expanded to 75%, Vdc likewise increments to 3/fourth of Vs and if obligation is diminished to 25%, Vdc lessens to 1/fourth of Vs. In this manner as heartbeat width differs the normal output voltage shifts. So we need to apply PWM to DC motor to fluctuate its velocity. 

Clearly the following inquiry is how to produce PWM? 

Any guesses...........? 

Yes, the answer is IC NE555. This chip can be utilized to create PWM. Here is the IC NE555 circuit to create PWM output 

Associations: IC NE555 is associated in astable mode. +12 biasing is given to Vcc pin (8). Reset pin (4) is additionally given +Ve supply to empower inner flip failure. Two diodes associated consecutive at release pin (7). One 1K resistor is associated in the middle of Vcc and release pin. A 10 K pot alongside two diodes D1 and D2 is associated between limit pin (6) and release pin in a manner that as it is expanded, the resistance for charging capacitor increments and resistance for releasing capacitor diminishes. 

Operation: when supply is given to circuit, the capacitor charges through R2-D2-R1A. The output of circuit is high. At the point when capacitor charges to 2/3 Vcc, the inward limit comparator gives output that makes circuit output low. So if R1 is expanded - R1A is more - capacitor charging time expanded – high output time (Ton) is more – obligation cycle is more. Subsequently capacitor releases through R1B – D1. So if R1 is diminished – R1B is more – capacitor releasing time is expanded – low output time (Toff) is more – obligation cycle is less. 

So this circuit produces PWM and width of heartbeat changes as pot R1 is fluctuated. 

At long last we require transistor H span circuit to adjust the course of DC motor and IC NE555 based PWM generator circuit to differ the pace of DC motor. Here is the finished circuit. 

The output of PWM generator circuit is given to H-Bridge circuit through SPDT switch. As we change the position of SPDT switch, the sign is either connected to Q1 and Q4 or Q2 and Q3. So the SPDT switch adjusts the heading of motor. What's more, the pot R1 differs width of output heartbeat connected to H-span circuit. So it changes the rate of motor. 

Here is the snap of circuit based on bread board 



So this is the basic circuit control pace and bearing of DC motor. It can control DC motors having 12 V or 500 mA current rating. For higher voltage or current rating motors one can utilize darlington pair transistors (TIP122, TIP142 and so forth) or force MOSFETS (IRF arrangement) or even SCR (TYN series)








DC Motor Control Using H Bridge DC Motor Control Using H Bridge Reviewed by Unknown on 15:07:00 Rating: 5

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