Using Transistors and Driving Motors - Exploring Arduino: Tools and Techniques for Engineering Wizardry - page 72

const int POT=0; //POT on Analog Pin 0
int val = 0;
void setup()
{
pinMode (MOTOR, OUTPUT);
}
void loop()
{
val = analogRead(POT);
val = map(val, 0, 1023, 0, 255);
analogWrite(MOTOR, val);
}
A lot of this code should look familiar from your previous experience dealing
with analog sensors. Note that the constrain function is not required when
using a potentiometer, because you can use the entire input range, and the value
will never go below 0 or above 1023 . After uploading the code to your Arduino,
adjust the pot and observe the speed of the motor changing accordingly.
UsinganH-BridgetoControlDCMotorDirection
So, you can change DC motor speed. This is great for making wheels on an
Arduino-controlled robot… as long as you only want it to drive forward. Any
useful DC motor needs to be able to spin in two directions. To accomplish this,
you can use a handy device called an H-bridge . The operation of an H-bridge
can best be explained with a diagram (see Figure 4-5).
Figure 4-5: H-bridge operation