![]() ![]() The L293D dual H-bridge has two H-bridges in the chip, so it will work nicely for this purpose. ![]() The easiest way to reverse the polarity in the coils is to use a pair of H-bridges. However, instead of using four coils, you use the both poles of the two coils, and reverse the polarity of the current. To control a bipolar stepper motor, you give the coils current using to the same steps as for a unipolar stepper motor. Wires 5 and 6 are wired to the supply voltage. To control a unipolar stepper, you use a Darlington Transistor Array. To control the stepper, apply voltage to each of the coils in a specific sequence. Higher than 24V is less common for small steppers, and frankly, above that level it’s best not to guess. Typical voltages for a stepper might be 5V, 9V, 12V, 24V. ![]() It is possible to damage a motor this way, so don’t go too far. 1 to 2 or 3 to 4) and slowly raise the voltage until the motor is difficult to turn. Ideally you’ll know the voltage from the manufacturer, but if not, get a variable DC power supply, apply the minimum voltage (hopefully 3V or so), apply voltage across two wires of a coil (e.g. Like other motors, stepper motors require more power than a microcontroller can give them, so you’ll need a separate power supply for it. not attached to the same coil), you should see infinite resistance (or no continuity). If you’ve got the leads of your meter connected to two wires that are not connected (i.e. You should find two pairs of wires with equal resistance. You can distinguish them from unipolar steppers by measuring the resistance between the wires. They have two independent sets of coils instead. Unlike unipolar steppers, bipolar steppers have no common center connection. The bipolar stepper motor usually has four wires coming out of it. They are called unipolar steppers because power always comes in on this one pole. The center connections of the coils are tied together and used as the power connection. The unipolar stepper motor has five or six wires and four coils (actually two coils divided by center connections on each coil). There are two basic types of stepper motors, unipolar steppers and bipolar steppers. They are used in printers, disk drives, and other devices where precise positioning of the motor is necessary. This design allows for very precise control of the motor: by proper pulsing, it can be turned in very accurate steps of set degree increments (for example, two-degree increments, half-degree increments, etc.). The center shaft has a series of magnets mounted on it, and the coils surrounding the shaft are alternately given current or not, creating magnetic fields which repulse or attract the magnets on the shaft, causing the motor to rotate. A stepper motor is a motor controlled by a series of electromagnetic coils. ![]()
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