Stepper motor control with the PIC - Revision history

Lynch at 22:41, 2 March 2008

2008-03-02T22:41:53Z

DavidEvitt: /* Code */

2008-02-19T20:40:46Z

Code

DavidEvitt: /* Overview */

2008-02-19T20:39:54Z

Overview

DavidEvitt: /* Overview */

2008-02-19T20:36:34Z

Overview

DavidEvitt: /* Overview */

2008-02-19T20:13:36Z

Overview

DavidEvitt: /* Overview */

2008-02-19T20:12:47Z

Overview

Lynch: /* Original Assignment */

2008-02-10T02:38:32Z

Original Assignment

Lynch: /* Overview */

2008-02-10T02:30:56Z

Overview

DavidEvitt: /* Code */

2008-02-06T18:45:45Z

Code

DavidEvitt: /* Overview */

2008-02-06T18:42:42Z

Overview

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-== Original Assignment ==
-The project is to use an interrupt to achieve stepper motor control along arbitrary motion profiles (e.g., mathematical functions of time, including constant velocity profiles).  For example, if your interrupt is at 1 ms, you can compare your step count at the current time to the desired step count at the current time and step the motor forward, backward, or not at all, as appropriate.  A simpler variant of this is constant speed control:  the main program sets the speed, and the interrupt determines whether or not to step the motor at each interrupt time.  Your documentation must provide evidence that the interrupt service routine always completes in less time than the time between interrupts (e.g., you can use the oscilloscope and look at a pin going high at the beginning of the ISR and low at the end).
-Also, stepper motors tend to have relatively low torque, but are capable of high speeds.  To improve the torque, we can add a gearhead or other transmission element.  It is convenient to have the motor and gearhead in a single package, so if you see a relatively inexpensive stepper motor + gearhead combination in an appropriate size, let us know!
 == Overview ==

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 == Code ==
-* [[media:stepper_control.c|stepper_control.c]] - Code can be found here.
+* [[media:main.c|stepper_control.c]] - Code can be found here.
 ==Further Reading==

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 Stepper motors are particularly useful devices because they can generate precise movement open loop.  There is lots of information about stepper motors on the web and the wiki.  Refer to the further reading section below as a place to get started.
-This page provides explanation of the circuitry and example code for driving the [[Actuators Available in the Mechatronics Lab#Stepper_Motors|Jameco 163395 8.4V bipolar stepper motor]] available in the mechatronics lab.  The motor is connected to a L293B H-bridge chip controlled by the logic outputs from the PIC.  The PIC reads the voltage from a potentiometer connected to an analog input and converts it to a desired speed and number of interrupt service routine (ISR) calls until stepping.  The ISR drives the logic outputs controlling the H-bridge and motor.
+This page provides explanation of the circuitry and example code for driving the [[Actuators Available in the Mechatronics Lab#Stepper_Motors|Jameco 163395 8.4V bipolar stepper motor]] available in the mechatronics lab.  The rated motor voltage is 8.4 volts but the motor should be able to handle up to 12V.  When operating at higher voltages be mindful of the possibility of overheating.  In this example, we used 8.6V.  The motor is connected to a L293B H-bridge chip controlled by the logic outputs from the PIC.  The PIC reads the voltage from a potentiometer connected to an analog input and converts it to a desired speed and number of interrupt service routine (ISR) calls until stepping.  The ISR drives the logic outputs controlling the H-bridge and motor.
 This stepper motor contains two windings, each of which has a set of two wires that allow for polarity control.  One winding is operated by the blue and red wires, while the other is controlled by the yellow and white wires.

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 This stepper motor contains two windings, each of which has a set of two wires that allow for polarity control.  One winding is operated by the blue and red wires, while the other is controlled by the yellow and white wires.
-The ISR completes in about 2.5 us.  Which means that the motor can be commanded to step extremely quickly.  However, the rotor can only keep up with the signal for a limited range, and can move one full step every ~1.2 ms.
+The ISR completes in about 2.5 us.  Which means that the motor can be commanded to step extremely quickly.  However, the rotor can only keep up with the signal for a limited range, and can move one full step every ~1.2 ms.  With a mass attached to the output shaft the maximum speed will decrease.
 == Circuit ==

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 Stepper motors are particularly useful devices because they can generate precise movement open loop.  There is lots of information about stepper motors on the web and the wiki.  Refer to the further reading section below as a place to get started.
-This page provides explanation of the circuitry and example code for driving the [[Actuators Available in the Mechatronics Lab|Jameco 163395 8.4V bipolar stepper motor]] available in the mechatronics lab.  The motor is connected to a L293B H-bridge chip controlled by the logic outputs from the PIC.  The PIC reads the voltage from a potentiometer connected to an analog input and converts it to a desired speed and number of interrupt service routine (ISR) calls until stepping.  The ISR drives the logic outputs controlling the H-bridge and motor.
+This page provides explanation of the circuitry and example code for driving the [[Actuators Available in the Mechatronics Lab#Stepper_Motors|Jameco 163395 8.4V bipolar stepper motor]] available in the mechatronics lab.  The motor is connected to a L293B H-bridge chip controlled by the logic outputs from the PIC.  The PIC reads the voltage from a potentiometer connected to an analog input and converts it to a desired speed and number of interrupt service routine (ISR) calls until stepping.  The ISR drives the logic outputs controlling the H-bridge and motor.
 This stepper motor contains two windings, each of which has a set of two wires that allow for polarity control.  One winding is operated by the blue and red wires, while the other is controlled by the yellow and white wires.