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 NXP Semiconductors

  • Stepper Motor

  • Created: Sep 04, 2014

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This project is a simple, low-cost hardwired stepper motor control circuit that can be used in applications that require moving parts but at the same time only consumes minimum power. The circuit is comprised of a 555 timer IC configured as an astable multivibrator with 1Hz frequency.

The output of the 555 timer is used as a clock for two 7474 dual "D" flip-flops that are set as a ring counter. When the power is initially switched ON, only the first flip-flop is set and the other three flip-flops are reset. Upon the receipt of a clock pulse the logic 1 output of the first flip-flop gets shifted to the second flip-flop. Therefore, with every clock pulse, the logic 1 output keeps shifting in a ring fashion. Q outputs of a;; the four flip-flps are amplified by a darlington transistor arrays inside the ULN2003 and connected to the stepper motor windings.

The project uses the 74F74 IC which is a dual positive edge-triggered D-type flip-flop featuring individual data, clock, set, and reset inputs; also true and complementary outputs. Set (SD) and reset (RD) are asynchronous active low inputs and operate independently of the clock input. When set and reset are inactive (high), data at the D input is transferred to the Q and Q outputs on the low-to-high transition of the clock. Data must be stable just one setup time prior to the low-to-high transition of the clock for predictable operation. Clock triggering occurs at a voltage level and is not directly related to the transition time of the positive-going pulse. Following the hold time interval, data at the D input may be changed without affecting the levels of the output.



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