The 80x86 IBM PC and Compatible Computers- P9: Praised by experts for its clarity and topical breadth, this visually appealing, one-stop source on PCs uses an easy-to-understand, step-by-step approach to teaching the fundamentals of 80x86 assembly language programming and PC architecture. Offering users a fun, hands-on learning experience, it uses the Debug utility to show what action the instruction performs, then provides a sample program to show its application. | for the motor Figure 12-8. 8255 Connection to Stepper Motor Steps per second and RPM relation The relationship between the RPM revolutions per minute steps per revolution and steps per second is intuitive and is as follows. RPM x Steps per revolution Steps per second - -------------------------------- The four-step sequence and number of teeth on rotor The switching sequence shown above in Table 12-5 is called the 4-step switching sequence since after four steps the same two windings will be ON . How much movement is associated with these four steps After completing every four steps the rotor moves only one tooth pitch. Therefore in a stepper motor with 200 steps per revolution its rotor has 50 teeth since 4 x 50 200 steps are needed to complete one revolution. This leads to the conclusion that the minimum step angle is always a function of the number of teeth on the rotor. In other words the smaller the step angle the more teeth the rotor passes. See Example 12-3. Looking at Example 12-3 one might wonder what happens if we want to move 45 degrees since the steps are 2 degrees each. To allow for finer resolutions all stepper motors allow what is called an 8-step switching sequence. The 8-step sequence is also called half-stepping since in following the 8-step sequence each step is half of the normal step angle. For example a motor with a 2-degree step angle can be used as a 1 -degree step angle if the sequence of Table 12-7 is applied. AyitfTE atermark. 365 Example 12-3 Give the number of times the 4-step sequence in Table 12-5 must be applied to a stepper motor to make an 80-degree move if the motor has a 2-degree step angle. Solution A motor with a 2-degree step angle has the following characteristics Step angle 2 degrees Steps per revolution 180 Number of rotor teeth 45 Movement per 4-step sequence 8 degrees To move the rotor 80 degrees we need to send 10 four-step sequences right after each other since 10x4 steps x 2 degrees 80 degrees. .
