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Detailed study on the subdivision technology of stepping motor
The stepper motor subdivision technology employs a specialized chip called TA8435H, which significantly streamlines the hardware design process. This chip integrates two H-bridge high-voltage, high-current dual-bridge drivers along with two chopper circuits to precisely control the current in the two-phase coils. It accepts standard TTL logic level signals to drive stepper motors with a maximum voltage of 40V and up to 2.5A per phase. Additionally, it features an enable input that lets you activate or deactivate the device independently of the input signals. The emitters of the lower arms of both bridges are connected externally via a sense resistor. There’s also an extra power input to ensure the logic operates efficiently at low voltages.
The motor control unit relies on the high-performance microcontroller mega16 as its primary controller. The mega16 boasts an advanced reduced instruction set architecture, featuring 16K bytes of in-system programmable Flash memory, 1K bytes of on-chip SRAM, an internal RC oscillator, and multiple operational modes, all within a broad voltage range (2.7V to 5.5V).
For the X and Y axes, where no subdivision is required, a unipolar motor with minimal current is used. The driver chip ULN2803 ensures reliable performance. However, the Z-axis, which focuses on precision, demands a motor capable of handling larger currents and requiring subdivision capabilities. Here, the TA8435H chip drives a bipolar motor. To mitigate potential interference from the high current motor to the microcontroller unit (MCU), optocoupler isolation is employed between the MCU and the TA8435H chip. Furthermore, the logic circuitry of the TA8435H is powered by a separate voltage regulator chip, LM7805, isolating it from the MCU. By controlling the M1, M2, CW/CWW, ENABLE, and CK1 pins of the TA8435H, the motor can be reversed, operated in coarse mode (without subdivision), or fine-tuned using an 8-step subdivision function.
In summary, this system combines advanced hardware and software solutions to provide precise motor control while minimizing interference and ensuring efficient operation across multiple axes.