Give full play to the role of the driver module . First of all, we need to understand PWM This concept .
PWM
Pulse width modulation (PWM) Basic principles ： The control mode is to control the switching device of inverter circuit , A series of pulses with equal amplitude are obtained at the output , Use these pulses instead of sine waves or required waveforms . That is to say, multiple pulses are generated in the half cycle of the output waveform , The equivalent voltage of each pulse is sinusoidal , The obtained output is smooth and has less low order harmonics . The width of each pulse is modulated according to certain rules , The output voltage of inverter circuit can be changed , The output frequency can also be changed .
tool / raw material
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Driver module ,arduino modular , DuPont line , Bus bar , Car
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ArduinoIDE, wait
method / step
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Drive module wiring
In the previous tutorial, I have said that if you want to control the output of the driver , Need to drive “ENA”“ENB” Control , Therefore, we need to pull out the two jumper caps of the selected part in the figure . And will “ENA” connect Arduino
UNO Development board “5” Pin ,“ENB” connect “6” Pin .
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Arduino The code test is as follows ：
int leftCounter=0, rightCounter=0;
unsigned long time = 0, old_time = 0; // Time stamp
unsigned long time1 = 0; // Time stamp
float lv,rv;// Left , Right wheel speed
#define STOP 0
#define FORWARD 1
#define BACKWARD 2
#define TURNLEFT 3
#define TURNRIGHT 4
#define CHANGESPEED 5
int leftMotor1 = 16;
int leftMotor2 = 17;
int rightMotor1 = 18;
int rightMotor2 = 19;
bool speedLevel=0;
int leftPWM = 5;
int rightPWM = 6;
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
attachInterrupt(0,RightCount_CallBack, FALLING);
attachInterrupt(1,LeftCount_CallBack, FALLING);
pinMode(leftMotor1, OUTPUT);
pinMode(leftMotor2, OUTPUT);
pinMode(rightMotor1, OUTPUT);
pinMode(rightMotor2, OUTPUT);
pinMode(leftPWM, OUTPUT);
pinMode(rightPWM, OUTPUT);
}
void loop() {
// put your main code here, to run repeatedly:
SpeedDetection();
if(Serial.available()>0)
{
char cmd = Serial.read();
Serial.print(cmd);
motorRun(cmd);
if(speedLevel) // Output different speeds according to different gears
{
analogWrite(leftPWM, 120);
analogWrite(rightPWM, 120);
}
else
{
analogWrite(leftPWM, 250);
analogWrite(rightPWM, 250);
}
}
}
/*
* * Speed calculation
*/
bool SpeedDetection()
{
time = millis();// In Milliseconds , Calculate current time
if(abs(time - old_time) >= 1000) // If the time is up 1 second
{
detachInterrupt(0); // Turn off external interrupt 0
detachInterrupt(1); // Turn off external interrupt 1
// Count the number of pulses per second from the encoder , Convert to current speed value
// What is the unit of speed per minute , Namely r/min. The encoder disk is 20 A void .
Serial.print("left:");
lv =(float)leftCounter*60/20;// Trolley wheel motor speed
rv =(float)rightCounter*60/20;// Trolley wheel motor speed
Serial.print("left:");
Serial.print(lv);// Upload the current high speed of the left wheel motor to the upper computer , Low byte
Serial.print(" right:");
Serial.println(rv);// Upload the current high speed of the left wheel motor to the upper computer , Low byte
// Return to the initial state of encoder speed measurement
leftCounter = 0; // Clear the pulse count to zero , In order to calculate the next second pulse count
rightCounter = 0;
old_time= millis(); // Record the time node of speed measurement per second
attachInterrupt(0, RightCount_CallBack,FALLING); // Reopen external interrupt 0
attachInterrupt(1, LeftCount_CallBack,FALLING); // Reopen external interrupt 0
return 1;
}
else
return 0;
}
/*
* * Interrupt service function of right wheel encoder
*/
void RightCount_CallBack()
{
rightCounter++;
}
/*
* * Interrupt service function of left wheel encoder
*/
void LeftCount_CallBack()
{
leftCounter++;
}
/*
* * Car motion control function
*/
void motorRun(int cmd)
{
switch(cmd){
case FORWARD:
Serial.println("FORWARD"); // Output status
digitalWrite(leftMotor1, HIGH);
digitalWrite(leftMotor2, LOW);
digitalWrite(rightMotor1, HIGH);
digitalWrite(rightMotor2, LOW);
break;
case BACKWARD:
Serial.println("BACKWARD"); // Output status
digitalWrite(leftMotor1, LOW);
digitalWrite(leftMotor2, HIGH);
digitalWrite(rightMotor1, LOW);
digitalWrite(rightMotor2, HIGH);
break;
case TURNLEFT:
Serial.println("TURN LEFT"); // Output status
digitalWrite(leftMotor1, HIGH);
digitalWrite(leftMotor2, LOW);
digitalWrite(rightMotor1, LOW);
digitalWrite(rightMotor2, HIGH);
break;
case TURNRIGHT:
Serial.println("TURN RIGHT"); // Output status
digitalWrite(leftMotor1, LOW);
digitalWrite(leftMotor2, HIGH);
digitalWrite(rightMotor1, HIGH);
digitalWrite(rightMotor2, LOW);
break;
case CHANGESPEED:
Serial.println("CHANGE SPEED"); // Output status
if(speedLevel) // Switch gears when receiving shift command
speedLevel=0;
else
speedLevel=1;
break;
default:
Serial.println("STOP"); // Output status
digitalWrite(leftMotor1, LOW);
digitalWrite(leftMotor2, LOW);
digitalWrite(rightMotor1, LOW);
digitalWrite(rightMotor2, LOW);
}
}
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For the sake of your understanding , Here is a special explanation ：
In the main function void loop() Add in PWM Output function ,analogWrite(pin,
value) Function “pin” Represents the pin used ,“value” Represents output PWM The size of the value , The scope is 0~255.
if(speedLevel) // Output different speeds according to different gears
{
analogWrite(leftPWM, 120); analogWrite(rightPWM, 120);
}
else
{
analogWrite(leftPWM, 250); analogWrite(rightPWM, 250);
}
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