PIC18F4520: PWM Motor Control - Revision history

LIMS: /* Sample Code */

2007-07-05T15:23:03Z

Sample Code

LIMS: /* Sample Code */

2007-07-05T15:21:12Z

Sample Code

LIMS: /* Sample Code */

2007-07-05T15:19:19Z

Sample Code

LIMS at 18:01, 2 July 2007

2007-07-02T18:01:38Z

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2007-06-27T16:33:32Z

Available Pins

LIMS: /* Available Pins */

2007-06-27T16:33:13Z

Available Pins

LIMS: /* Circuit Diagram */

2007-06-27T16:29:02Z

Circuit Diagram

LIMS: /* Sample Code */

2007-06-27T16:26:48Z

Sample Code

LIMS: /* Bidirectional Motor Control */

2007-06-27T16:25:44Z

Bidirectional Motor Control

LIMS: /* Circuit Diagram */

2007-06-27T16:24:28Z

Circuit Diagram

@@ Line 100: / Line 100: @@
 as functions of "read". Note that the value of "readhigh"
 varies from 0 to 255 when the potentiometer is between
-and 255, and "readlow" behaves similarly.
+and 255, and "readlow" varies between 255 and 0 when the
+potentiometer is between 0 and 120.
          read = read_adc();

@@ Line 62: / Line 62: @@
 First include header file with definitions for specific PIC.
-Set fuses.  HS is type of external clock, low voltage protection
+Set fuses.  HS is type of external clock, low voltage programming
 (LVP) is off, and the watchdog timer (WDT) is off.
 External clock frequency of 20 MHz is specified.

@@ Line 14: / Line 14: @@
 First include header file with definitions for specific PIC.
-Set fuses.  HS is type of external clock, low voltage protection
+Set fuses.  HS is type of external clock, low voltage programming
 (LVP) is off, and the watchdog timer (WDT) is off.
 External clock frequency of 20 MHz is specified.
@@ Line 51: / Line 51: @@
      }
    }
 ===Circuit Diagram===
 [[Image:pwmckt.jpg]]

@@ Line 1: / Line 1: @@
-Pulse Width Modulation, or PWM, is a technique used to vary the ''average'' magnitude of a signal by changing its '''duty cycle''' (the proportion of time that a signal is active or "high").  For a moe in-depth introduction to PWM motor control click [[Pulse Width Modulation|here]].
+Pulse Width Modulation, or PWM, is a technique used to vary the ''average'' magnitude of a signal by changing its '''duty cycle''' (the proportion of time that a signal is active or "high").  For a more in-depth introduction to PWM motor control click [[Pulse Width Modulation|here]].
 ==Available Pins==
 The PIC18F4520 is capable of outputing a PWM signal on two separate channels:  CCP1 and CCP2 (shown below). The red pins have the capability of outputing PWM, while the grey are usually committed to communication or power.

@@ Line 1: / Line 1: @@
 Pulse Width Modulation, or PWM, is a technique used to vary the ''average'' magnitude of a signal by changing its '''duty cycle''' (the proportion of time that a signal is active or "high").  For a moe in-depth introduction to PWM motor control click [[Pulse Width Modulation|here]].
 ==Available Pins==
-The PIC18F4520 is capable of outputing a Pulse Width Modulation signal on two separate channels:  CCP1 and CCP2 (shown below). The red pins have the capability of outputing PWM, while the grey are usually committed to communication or power.
+The PIC18F4520 is capable of outputing a PWM signal on two separate channels:  CCP1 and CCP2 (shown below). The red pins have the capability of outputing PWM, while the grey are usually committed to communication or power.
 <br><br>
 [[Image:4520pindiagramPWM.jpg||center]]

← Older revision		Revision as of 16:29, 27 June 2007
Line 122:		Line 122:

	===Circuit Diagram===		===Circuit Diagram===
			[[Image:bipwmckt.jpg]]

@@ Line 54: / Line 54: @@
 ==Bidirectional Motor Control==
+This section will detail how to set up bidirectional motor control using a PIC microcontroller and PWM.
 ===Sample Code===
 Program to run a motor bidirectionally at varying speeds depending
@@ Line 119: / Line 120: @@
      }
    }
 ===Circuit Diagram===

@@ Line 54: / Line 54: @@
 ==Bidirectional Motor Control==
+===Sample Code===
+Program to run a motor bidirectionally at varying speeds depending
+on the position of a potentiometer.
+First include header file with definitions for specific PIC.
+Set fuses.  HS is type of external clock, low voltage protection
+(LVP) is off, and the watchdog timer (WDT) is off.
+External clock frequency of 20 MHz is specified.
+   #include <18F4520.h>
+   #fuses HS,NOWDT,NOPROTECT,NOLVP
+   #use delay(clock=20000000)
+Introduce the variables to be used in the main program.
+   int read;
+   int readlow;
+   int readhigh;
+Begin main body of program.
+   void main() {
+Setup the CCP1 and CCP2 to be PWM outputs. Also set the timer
+to be used for PWM.
+      setup_ccp1(CCP_PWM);
+      setup_ccp2(CCP_PWM);
+      setup_timer_2(T2_DIV_BY_1, 255, 1);
+Setup analog input, and which analog channel is active.
+      setup_adc_ports(AN0_ANALOG);
+      setup_adc(ADC_CLOCK_INTERNAL);
+      set_adc_channel(0);
+Setup an infinite loop, using a while statement.
+      while(TRUE) {
+Read the analog input and define "readhigh" and "readlow"
+as functions of "read". Note that the value of "readhigh"
+varies from 0 to 255 when the potentiometer is between
+and 255, and "readlow" behaves similarly.
+         read = read_adc();
+         readlow = (120-read)*2.125;
+         readhigh = (read-140)*2.217;
+Check the value of "read", and set the duty cycle of each PWM
+output signal accordingly.  The H-bridge circuit used requires
+two inputs (the two PWM outputs of the 18F4520) to control the
+direction and speed of the driven motor.
+         if (read<120){
+            set_pwm1_duty(readlow);
+            set_pwm2_duty(0);}
+         else if (read>140){
+            set_pwm1_duty(0);
+            set_pwm2_duty(readhigh);}
+         else {
+            set_pwm1_duty(0);
+            set_pwm2_duty(0);}
+     }
+   }
+===Circuit Diagram===