AutoCar
Usually this is obtained with an H-Bridge controller.
The H-Bridge is designed to drive a motor clockwise and anticlockwise. To reverse a motor, the supply must be reversed and this is what the H-Bridge does.
An H-Bridge can be made with SWITCHES, RELAYS, TRANSISTORS or MOSFETS.
For a project such as a robot or car, we need an ELECTRONIC circuit - one that is controlled by a "CONTROL CIRCUIT". The Control Circuit outputs a signal (or a number of signals) to control an H-Bridge.
Here is a sample circuit. The Control Circuit consists of the first 3 transistors. These amplify the signal from the electret microphone and produce a signal that is able to charge a 47u electrolytic. The next two transistors provide inverted signals to the H-Bridge and are part of the Control Circuit. The H-Bridge consists of the last 4 transistors.
Using a Joystick directly connected to Ardway Digital PINs it is possible to manage engines exactly as a mini cart.
The application written for the Arduino board is able to modulate acceleration using an incremetal algorithm (showed below). This in order to avoid accidents due to the fast acceleration or deceleration
The connection schema is described here
Usually this is obtained with an H-Bridge controller.
The H-Bridge is designed to drive a motor clockwise and anticlockwise. To reverse a motor, the supply must be reversed and this is what the H-Bridge does.
An H-Bridge can be made with SWITCHES, RELAYS, TRANSISTORS or MOSFETS.
For a project such as a robot or car, we need an ELECTRONIC circuit - one that is controlled by a "CONTROL CIRCUIT". The Control Circuit outputs a signal (or a number of signals) to control an H-Bridge.
Here is a sample circuit. The Control Circuit consists of the first 3 transistors. These amplify the signal from the electret microphone and produce a signal that is able to charge a 47u electrolytic. The next two transistors provide inverted signals to the H-Bridge and are part of the Control Circuit. The H-Bridge consists of the last 4 transistors.
The 2 motors can be controlled using an easy library over the serial port so, in order to use it via Arduino, you will need to connect it to the Serial port of arduino (To be more detailed you will need to be connected to one of the available serial port, depending on which
arduino you will use) and send the right commands. In the following c++ code used to run the Ardway Autocar Function, you will not see the protocoll used but the functions defined for each movement of the joystick. Later in the page I will present some example of the protocoll
AutoDrive source code
if (currMode == AUTOMODE) //Drive it manually
{
//Read Joystick values
SteerLeftPin = digitalRead(STEERINGLEFTPIN);
SteerRightPin = digitalRead(STEERINGRIGHTPIN);
balancelForward = digitalRead(BALANCEFORWARDPIN);
balancelBackward = digitalRead(BALANCEBACKWARDPIN);
DBGString[0] = '\0';
//Maintain maximum speed
if (curAutoSpeed > SABER_MOTOR1_HALF_FORWARD)
curAutoSpeed = SABER_MOTOR1_HALF_FORWARD;
if (SteerLeftPin == 0) {
SerialTransfer.isBack = false;
if (previousDirection == 99) {
previousDirection = LEFT;
curAutoSpeed = 1;
}
else if (previousDirection == LEFT)
curAutoSpeed = curAutoSpeed + SPEEDINCREMENT;
else {
previousDirection = LEFT;
curAutoSpeed = 1;
}
if ((curAutoSpeed % 5) == 0) { //Delay the string
sprintf(DBGString, "Turn RIGHT: %d\r", curAutoSpeed); //wrong string due to an error
SerialTransfer.SendDisplayString((char*)DBGString,0);
DBGString[0] = '\0';
}
//and now turn left
autoTurnLeft();
delay(50); //Slow down to delay cicles
}
else if (SteerRightPin == 0) {
SerialTransfer.isBack = false;
if (previousDirection == 99) {
previousDirection = RIGHT;
curAutoSpeed = 1;
}
else if (previousDirection == RIGHT)
curAutoSpeed = curAutoSpeed + SPEEDINCREMENT;
else {
previousDirection = RIGHT;
curAutoSpeed = 1;
}
//Turn right
if ((curAutoSpeed % 5) == 0) { //Delay the string
sprintf(DBGString, "Turn LEFT: %d\r", curAutoSpeed); //wrong string due to an error
SerialTransfer.SendDisplayString((char*)DBGString,0);
DBGString[0] = '\0';
}
autoTurnRight();
delay(50); //Slow down to delay cicles
}
else if (balancelForward == 0) {
SerialTransfer.isBack = false;
if (previousDirection == 99) {
previousDirection = FORWARD;
curAutoSpeed = 1;
}
else if (previousDirection == FORWARD)
curAutoSpeed = curAutoSpeed + SPEEDINCREMENT;
else {
previousDirection = FORWARD;
curAutoSpeed = 1;
}
if ((curAutoSpeed % 5) == 0) { //Delay the string
sprintf(DBGString, "Go FORWARD: %d\r", curAutoSpeed);
SerialTransfer.SendDisplayString((char*)DBGString,0);
DBGString[0] = '\0';
}
autoGoForward();
delay(50); //Slow down to delay cicles
}
else if (balancelBackward == 0) {
SerialTransfer.isBack = true;
if (previousDirection == 99) {
previousDirection = BACKWORD;
curAutoSpeed = 1;
}
else if (previousDirection == BACKWORD)
curAutoSpeed = curAutoSpeed + SPEEDINCREMENT;
else {
previousDirection = BACKWORD;
curAutoSpeed = 1;
}
if ((curAutoSpeed % 5) == 0) { //Delay the string
sprintf(DBGString, "Go BACKWORD: %d\r", curAutoSpeed);
SerialTransfer.SendDisplayString((char*)DBGString,0);
DBGString[0] = '\0';
}
//go backward
autoGoBackward();
delay(50); //Slow down to delay cicles
}
else
{
if (curAutoSpeed > 0) {
delay(50);
curAutoSpeed-=2;
switch (previousDirection){
case FORWARD:
autoGoForward();
break;
case BACKWORD:
autoGoBackward();
break;
case LEFT:
autoTurnLeft();
break;
case RIGHT:
autoTurnRight();
break;
}
}
else
{
previousDirection = 99;
}
Sabertooth serial protocoll
//This is the declaration of the Sabertooth object. SWSerial is the serial port used.
//In my case I am using the wire lib to create a virtual
//Serial port using a separate pin on the Arduino board
Sabertooth ST(128, SWSerial);
//This function must be used at the beginning of your code to initialise the serial communication
//The serial communication can be obtained using the "wire" library or using a direct serial connection
void initSabertooth (void) {
SWSerial.begin(9600);
ST.autobaud();
}
//In the stup function I strongly suggest to stop all motors using these commands
ST.motor(1, SABER_ALL_STOP);
ST.motor(2, SABER_ALL_STOP);
//This is an example of the turn right function
//Simply tell to the motor the speed that is from 0 to 128 for a forward speed
//and from -1 to -128 for a backuward speed
//Other functions can be obtained in the same way
void autoTurnRight() {
ST.motor(1, curAutoSpeed);
ST.motor(2, curAutoSpeed - (curAutoSpeed * 2));
}