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 Chapter 8. Advanced Experiments 8.2. Experiment with Stepping Motor Recently, loop pulse distributor is used to control the stepping motor. The loop pulse distributor can be composed by discrete devices, controlled by software, or dedicated integrated circuit. Generally, a full stepping motor controlling system consists of controller, driver and motor, like the below diagram.
controller Excitation Mode of Stepping Motor Usually, there are 3 excitation modes: 1 phase excitation, 2 phase excitation and 1-2 phase excitation. 1 phase mode is the easiest, but generates least torque. 2 phase mode generates better torque. 1-2 phase mode is a half-step mode, that is, the rotation angle is half the former 2 modes.
Stepping Motor Driving CircuitThe small stepping motor used in this section has no special requirements on driving voltage or current. Improvement must be taken when stepping motor is used in industrial design. The below picture shows the general driving circuit.
Most often, more than 1 driver is needed in practical applications. The above circuit requires many components, and space on PCB boards. Integrated circuits like ULN2003, ULN2803 are a better solution for multiple drivers. K8MDP contains ULN2003, which is high voltage, high current darlington arrays each containing seven open collector darlington pairs with common emitters. Each channel rated at 500mA and can withstand peak currents of 600mA. Suppression diodes are included for inductive load driving and the inputs are pinned opposite the outputs to simplify board layout. It is useful for driving a wide range of loads including solenoids, relays DC motors, LED displays filament lamps, thermal print heads and high power buffers. Schematic diagram of ULN2003 is shown at below pictures.
Below shows the classic application circuit with ULN2003.
Software Design for Stepping MotorFunctions: motor will rotate clockwise at system power on, it rotates counter-clockwise when key SW20 is depressed.
Loop pulse table for clockwise rotation:
Loop pulse table for counter-clockwise rotation:
Schematic Diagram
Program Flow Chart
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