Now here is the a H-Bridge motor driver that is made of transistors and can be controlled by an arduino,it is capable of changing the direction of the motor but not the speed.....

Step 1: Gathering the Materials

So here is the list of materials-
1.2N2907 PNP transistors x 2
2.2N2222 NPN transistors x 2
3.1 k ohm resistors x 4
4.1N914 diodes x 4
5.Copper clad board

Step 2: What Is an H-Bridge Motor Driver???

An H-Bridge motor driver circuit can be easily understood by looking at the images above,it mainly comprises of the two switches that is replaced by transistors in our circuit.....

Step 3: The Circuit...

The circuit can be easily understood by looking at the image above,the NPN and PNP transistors are used to switch the direction of the motor when the base pin is provided with current by our ARDUINO...

Step 4: Etching the Circuit...

I provided the pics,so that it may be easy for you to make the PCB design,I designed it use Eagle Cadsoft,you may use any software or you can also do it manually....

Step 5: The Completed Circuit.

After etching the circuit you may solder the components as shown,and may plug the Arduino pins in the motor control pins in the board(marked as "In 1 & 2" in the circuit diagram)and connect the motor pins in the motor terminals....

Step 6: The Arduino Code...

Copy paste the following program in your Arduino IDE and upload it,this program switches the motor's direction after every two seconds...

void setup() {
pinMode(13,OUTPUT);
pinMode(12,OUTPUT);
}

void loop(){
digitalWrite(13,HIGH);
digitalWrite(12,LOW);
delay(2000);
digitalWrite(13,LOW);
digitalWrite(12,HIGH);
delay(2000);
}