In this instructable, I will show you how to build an H Bridge - a simple electronic circuit which enables us to apply voltage to load in either direction. It is commonly used in robotics application to control DC Motors. By using H Bridge we can run DC Motor in clockwise or anticlockwise directions.
Step 1: Required Hardware
The following components have been used:
1. x1 7805 voltage regulator
2. x2 2N2907 PNP Transistor(Q1,Q3)
3. x2 2N2222 NPN Transistor(Q2,Q4)
4. x4 1N4004 Diode(D1.D2,D3,D4)
5. x4 1K Resistor(R1,R2,R3,R4)
6. x3 255SB SPDT sliding switch
7. x1 DC Jack ( 12V )
8. x2 2Pin Connector
9. x1 DC Motor
Step 2: Paper Schematic
The image shows a paper schematic of H-bridge DC Motor Driver Circuit. The above circuit has a drawback. I was facing a problem with Diode 1N5817 so I used 1N4004. The transistors Q1, Q2 & Q3, Q4 will not change its state because it is not connected to the ground point. These issues were fixed in the circuit schematic using Eagle software.
Step 3: Circuit Schematic & Working Principle
The image shows a circuit schematic of H-bridge DC Motor Driver using Eagle software.
In this circuit, all transistors are wired as switches. An NPN transistor (Q3 and Q4) will be ON when we give HIGH to it and a PNP transistor (Q1 and Q2) will be ON when we give LOW to it. So when (A = LOW, B = HIGH, C = LOW, D = HIGH), transistors Q1 & Q4 will be ON and Q2 & Q3 will be OFF, so the motor rotates in a clockwise direction. Similarly when (A = HIGH, B = LOW, C = HIGH, D = LOW), transistors Q2 & Q3 will be ON and transistor Q1 & Q4 will be OFF, thus the motor rotates in an anticlockwise direction.
1N4004 (D1 ~ D4) is used as a freewheeling diode as it is a fast switching diode. It avoids problems due to the negative voltage produced by the back emf the dc motor. Resistors R1 – R4 are used to limit the input current of transistors and are designed in such a way that transistor will work as a switch. 3 Sliding switches ( S1, S2 & S3 ) are used. S1 is used for ON & OFF function of the motor. S2 & S3 are used for Clockwise & Anticlockwise rotation of the motor.
Step 4: PCB Design
The image shows a circuit PCB Design of H-bridge DC Motor Driver using Eagle software.
Following are the parameter considerations for PCB design:
1. Trace width thickness is minimum 8 mil.
2. The gap between plane copper and copper trace is minimum of 8 mil.
3. The gap between a trace to trace is a minimum of 8 mil.
4. Minimum drill size is 0.4 mm
5. All the tracks which have current path need thicker traces
Step 5: Uploading Gerber on LionCircuits
PCB needs to be fabricated. I ordered my PCB from LionCircuits. You just have to upload your Gerber files online on their platform and place an order.
In the above image, you can see the PCB design after uploading on the LionCircuits platform.
Step 6: Fabricated Board
After testing in simulation, we can draw the PCB Schematic with any program you want.
Here I have attached my own design and Gerber files.
Step 7: Component Assembled Board
The image shows that the components are assembled on the board.
When I was working with this board, the input resistor with the value of 1k was creating a problem in the rotation of motor so I shorted all 1k resistors, then its work.
Step 8: OUTPUT
Step 9: Learning
I didn’t do this circuit in a breadboard first that's why I faced a lot of issues in the fabricated board. In my next design, I will make the circuit in breadboard first, after that, I will move on to the fabrication board and I advise you to do the same.