Understanding Stepper Motor Control
Stepper motors remain a recurring topic in electronics. This compact circuit serves to transform a clock signal, originating from a square wave generator, into signals featuring a crucial 90-degree phase difference. Such a phase difference is necessary for effectively driving the stepper motor windings. The simplicity of this setup does come with a trade-off: the frequency is reduced by a factor of four. However, this reduction poses no significant challenge, as compensating for it merely involves increasing the input frequency.
By examining the timing diagram, it becomes evident that the counter outputs of the 4017 are amalgamated using inverting OR gates. This integration results in the generation of two square waves with a precise phase difference, creating the accurate sequence required for powering the motor windings: first winding is negative, second winding is positive, both windings are negative, first winding is positive and second winding is negative, and lastly, both windings are positive. Internally, the 4017 features a divide-by-10 counter followed by a decoder. Output ‘0’ remains active (logic one) as long as the internal counter is at zero.
Generating Stepper Motor Sequences
Upon the arrival of the next positive edge of the clock signal, the counter advances to 1, causing output ‘1’ to become active. This progression continues until output ‘4’ turns into a logical one. This signal, linked to the reset input, promptly resets the counter back to the ‘zero’ state. The pulse generated by this process is incredibly brief, making it challenging to observe accurately without precise oscilloscope adjustments. Since the output of an OR gate can only provide limited current (several mA), it’s insufficient for driving a stepper motor directly. A suitable driver circuit, positioned between the generator and the stepper motor, was featured in the May 2004 issue of Elektor Electronics.
An oscilloscope, informally known as a scope, stands as an essential electronic test instrument graphically representing varying electrical voltages as a two-dimensional plot of one or more signals over time. This laboratory instrument is commonly utilized to display and analyze electronic signal waveforms. Essentially, the device generates a graph depicting the instantaneous signal voltage as a function of time, providing valuable insights into signal behavior and characteristics.