You are able to make things move by controlling motors with Arduino. Various types of motors exist that are suited for different applications. In this chapter you will learn how Arduino can drive differend kind of motors.
Controlling Servo Motors
In contrast to motors, servos enables you to control movement to a position instead of rotatating continiously. Servo motors are ideal if you would like to rotate things in a range of 0 to 180 degrees. Servos are also easy to control because the motor driver is built into the servo.
The servo motor has some control circuits and a potentiometer (a variable resistor, aka pot) connected to the output shaft. In the picture above, the pot can be seen on the right side of the circuit board. This pot allows the control circuitry to monitor the current angle of the servo motor.
If the shaft is at the correct angle, then the motor shuts off. If the circuit finds that the angle is not correct, it will turn the motor until it is at a desired angle. The output shaft of the servo is capable of traveling somewhere around 180 degrees. Usually, it is somewhere in the 210-degree range, however, it varies depending on the manufacturer. A normal servo is used to control an angular motion of 0 to 180 degrees. It is mechanically not capable of turning any farther due to a mechanical stop built on to the main output gear.
The power applied to the motor is proportional to the distance it needs to travel. So, if the shaft needs to turn a large distance, the motor will run at full speed. If it needs to turn only a small amount, the motor will run at a slower speed. This is called proportional control.
Controlling DC motors
A DC motor (Direct Current motor) is the most common type of motor. DC motors have two leads, one positive and one negative. If you connect these two leads to a battery the motor will rotate. If you switch the leads the motor will rotate in the opposite direction.
DC motors are available in many sizes. If you select a motor for a project please remember to ook at the torque of the motor. Torque determines how much work the motor can do. DC motors with higher toque can handle more but will also draw more current than lower torque motors.
There are two types of DC motors, brushless and brushed. Brushless motor are more powerfull and efficient but require more complicated electronic control while brushed DC motors are easier to handle.
A Stepper Motor or a step motor is a brushless, synchronous motor, which divides a full rotation into a number of steps. In contrast to brushless DC motors, which rotate continuously when a DC voltage is applied, stepper motors rotate in step angles.
Remember, one rotation consists of 360 degrees. Stepper motors can be bought with steps per revolution of 12,24,72,144,180 and 200. This wil result into stepping angles of 30,15,5,2.5,2 and 1.8 degress per step.
Stepper motors can thus turn an exact amount of degrees as desired. This will give you complete control over the motor and the ability to move it to an exact location and hold that position.
The most important thing you need to know is that, to move the stepper motor, you need to tell the motor in which directiion and which speed it needs to step.