Basic H-bridge motor driver circuit using bipolar transistor

A DC motor controller has many forms. I am going to suggest you learn an h-bridge motor driver circuit.

So what? It is easy to do with a transistor or MOSFET drivers. And they are high performance, too.

I know you like to build a circuit project than tricky principles.
However, if you are a beginner. Learning H-Bridge motor works. It is definitely worth your time.

I try to draw a circuit diagram that looks easy to see.

Often we can see this H-Bridge motor driver on many controller circuits to moving of a robot.

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How it works

We can design the circuit with MOSFET or transistor to control the rotating of a motor.

H-bridge switches

Which I suggest example them as switch, so easy to understand by see its working as Figure 1.

Figure 1: All the switches are OFF, causing the motor to not rotate.

In-circuit, we see that all switches are the open states. No the current flowing in the circuit, cause the DC motor can’t work.

Forwarding Mode

Then, look at Figure 2. When having the S1-switch (closed) and S3 (closed).

S1 S3 make motor works — **Figure 2: the switch-S1 and S3 are closed cause the motor rotates.**

It causes the motor to get the current. As we notice that the current flowing into the positive terminal of the motor.

Making the DC motor rotated in features of forwarding form. Or Rotate clockwise.

Reversed Mode

And, If both S4 and S2 are closed together. The Motor also get current that flow through them. But it will don’t the same first form. As Figure 3

S2 S4 OFF Motor reverse — **Figure 3: Both switch-S2 and S4 are closed, causes DC motor rotates back in counter-clockwise direction.**

Because that current will flow through the negative of motor cause current reversed or Rotated back counter-clockwise direction.

Start to apply transistors

We will try to use all the transistors as the switch. You see in Figure 4.

Basic transistor motor driver circuit — **Figure 4 Using the transistor as switches.**

When a base of transistors gets the current electricity. It causes the transistor running and the DC motor will rotate, too.

Bridge transistor Motor driver

As Figure 5, we use the four transistors to connected into the H-bridge circuit.

Using transistor Bridge as switch Motor control — **Figure 5: we use the four transistors as a switch controller.**

And add a diode to protect the electricity that may flow backward from the motor. Making damage to the transistor.

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Forward Rotate using transistors

In Figure 6 circuit, if we apply power to A-point. We will make Q1 and Q3-transistor works. Because they get IB-current into a base.

motor rotate forward using transistor H-Bridge control — **Figure 6: apply power into A-point, Q1 and Q3 work. The motor rotates forward directions.**

So, the motor will rotate on the forward direction. Because the electrical current flowing from Q1 into the positive of the motor. and flow through Q3 to ground successfully.

Recommended: 555 PWM LED dimmer circuit diagram

Reverse Rotate control using transistor

Then later as Figure 7, we change power supply-V1 point into B-point. The Q4 and Q2 also work by they get current from the base.

Apply Reverse motor using H-Bridge control — **Figure 7: The motor gets the current through Q4 and Q2. It rotates in reverse direction**

It makes them have the current flow through Q4 go to the negative of motor and through Q2-transistors to ground. Which flowing of current in this form causes the motor rotated in reverse direction.