![]() ![]() ![]() Four power MOSFETs are used to provide variable speed and reversing for DC motors. The hardware based PWM does not require any CPU overhead and leaves 25 MIPS available for user code.Ī full-bridge circuit can be used to drive a DC motor when reversing is required. ![]() ![]() The software example uses the ADC and one PCA module configured for 8-bit PWM mode. This circuit provides variable speed control of a DC motor with rotation in a single direction.Įxample 1 of AN191 - Motor Control Software Examples provides simple example code for a DC motor using the C8051F300 MCU. The simplest DC motor drive circuit consists of a single N-channel power MOSFET and a Schottky diode. The bipolar stepper motor has a higher parts count and Bill of Materials cost. Note that the polarity must be inverted for the high-side port pins. Four inexpensive NPN transistors in the common-base configuration can be used for bipolar stepper motors up to about 24 volts, (depending on the availability of 3 V Logic-Level Power MOSFETs). The upper transistors require a high-side drive circuit. The lower transistors can be driven directly from the MCU. Bipolar motors are driven by a dual H-bridge and utilize the entire motor winding. The software provided in AN155 can also be used to drive bipolar stepper motors with minor modifications. The software demonstrates a linear-velocity profiler with adjustable acceleration. The reference design board includes a C8051F300 MCU, four power MOSFETs to drive the stepper motor, a diode clamping circuit, a voltage regulator and a RS232 interface. The unipolar stepper motor system provides accurate positioning with the lowest parts count and bill of materials cost. The MCU can directly drive 3 V logic-level power MOSFETs. AN155 provides a complete reference design for unipolar stepper motors using the C8051F300 MCU. ![]()
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