Stepper motors differ from normal DC motors in that, rather than just spinning in one direction or another, they move in small increments in a given direction. The stepper has no feedback circuit, so if we hold the shaft of the motor, the Arduino will believe it is moving though the stepper might not be moving. stepper1.step(-100) Arduino assumes the stepper moves while it orders it to move. If, for example, we set 200 steps at a speed of 1 RPM, it will take one full minute until the Arduino will continue execution. Note that the step() function will pause the execution of the program until the motor spins completely. If we feed a negative number of steps, it will move in the opposite direction. Lastly, to make the motor move, we need to order the number of steps to increment. The speed of the motor can be changed at any time. If, for example, we set a speed of 60 RPM as in this case, and the motor has 200 steps, it will take around 5 milliseconds to increment one step. However, as this is a stepper, we always want full power so we will simplify and directly set the PWM pins always as HIGH: // PWM pins require declaration when used as DigitalpinMode(pwmA, OUTPUT) Īnother important step is declaring the speed at which we want the motor to turn. In a normal DC motor operation of the Motor Shield, the two PWM pins select how much power we attribute to each motor. The direction pins sets which direction the coils will be excited in: Stepper stepper1(200, dirA, dirB) We only need to declare the two direction pins of the Arduino Motor Shield. The syntax requires the number of steps of the motor as the first parameter and then the pins to which we connected the motor. The code declares a stepper motor, selects a speed, and makes it turn in both directions. This instructable and many more can be found in my Arduino Development Cookbook available here. They are also unipolar and the four center cables have to be connected together. Also, there are stepper motors with eight cables, but they are incredibly rare. There are some versions with only five cables that are also unipolar and already have the two center coils connected together internally. With six cables, it is most probably unipolar where the two center coil cables have to be connected together. A four-cable stepper motor is usually bipolar. This is a simple guide on identifying the type. A bipolar stepper motor, available at Sparkfun, Pololu, Adafruit or in an old printer.An Arduino board connected to a computer via USB.We can control a bipolar stepper motor using the Arduino Motor Shield. Luckily there are multiple Arduino compatible bipolar stepper drivers out there. To fully control one, two H-bridges are required. Bipolar stepper motors have much higher efficiency and torque however they are much harder to control. Unipolar stepper motors are easy to control at the cost of low efficiency and power. There are two types of stepper motors: unipolar and bipolar. Stepper motors are found in printers, scanners, industrial robot arms, 3D printers, and pretty much in every precision motion device. It gets interesting when we only tell it to go one step and it turns exactly 1.8 degrees. A typical motor has 200 steps per revolution if we tell the motor to go 100 steps in one direction, it will turn exactly 180 degrees. With the way it is designed, a stepper can only move from one step to the next and fix in that position. When we need precision and repeatability, a stepper motor is always the solution.
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