Thanksgiving is around the corner and the kids are old enough now to start programming at this level. Four years ago, the coding was likely going to be a bit over their heads, and had me scratching mine from time to time.
I'm starting with essentially, two kits. One familiar, and one new.
I'll be using a mix of Arduino, and likely, eventually, my Raspberry Pi 3.
I'm cannibalizing a Meccano G15 semi-humanoid robot. This is a steal as a starter kit as it comes with two 5v motors, 4 servos, and a 5v power source. The building platform translates to what should be a solid platform. It can be found for cheap, in this or the newer version. It was fun for the kids last weekend as intended out of the box.
I seem to have this working for the most part. I need to do some fine tuning, but should have it running pretty effectively shortly.
Da Code
const int pingPin = 7; // pin for ping input
const int dangerThresh = 10; //threshold for obstacles (in cm)
int leftDistance, rightDistance; //distances on either side
long duration; //time it takes to recieve PING))) signal
void setup() {
// initialize serial communication:
Serial.begin(9600);
//Setup Channel A
pinMode(12, OUTPUT); //Initiates Motor Channel A pin
pinMode(9, OUTPUT); //Initiates Brake Channel A pin
//Setup Channel B
pinMode(13, OUTPUT); //Initiates Motor Channel B pin
pinMode(8, OUTPUT); //Initiates Brake Channel B pin
}
void loop()
{
int distanceFwd = ping(); //set distance ahead to ping distance
if (distanceFwd > dangerThresh) //if path is clear
{
//MOVE FORWARD
//Motor A forward
digitalWrite(12, HIGH); //Establishes forward direction of Channel A
digitalWrite(9, LOW); //Disengage the Brake for Channel A
analogWrite(3, 255); //Spins the motor on Channel A
//Motor B Forward
digitalWrite(13, HIGH); //Establishes backward direction of Channel B
digitalWrite(8, LOW); //Disengage the Brake for Channel B
analogWrite(11, 255); //Spins the motor on Channel B
}
else //if path is blocked
{
digitalWrite(9, HIGH); //Engage the Brake for Channel A
digitalWrite(8, HIGH); //Engage the Brake for Channel B
delay(1000);
//MOVE BACK TURNING FIRST WAY
//Motor A Backwards
digitalWrite(12, LOW); //Establishes backward direction of Channel A
digitalWrite(9, LOW); //Disengage the Brake for Channel A
analogWrite(3, 175); //Spins the motor on Channel A
delay(1000);
rightDistance = ping(); //scan to the right
delay(1000);
digitalWrite(9, HIGH); //Engage the Brake for Channel A
digitalWrite(8, HIGH); //Engage the Brake for Channel B
delay(1000);
//return to center
//Motor B backwards
digitalWrite(13, LOW); //Establishes backward direction of Channel B
digitalWrite(8, LOW); //Disengage the Brake for Channel B
analogWrite(11, 175); //Spins the motor on Channel B
delay(1000);
digitalWrite(9, HIGH); //Engage the Brake for Channel A
digitalWrite(8, HIGH); //Engage the Brake for Channel B
delay(1000);
//MOVE BACK TURNING SECOND WAY
//Motor B Backwards
digitalWrite(13, LOW); //Establishes backward direction of Channel B
digitalWrite(8, LOW); //Disengage the Brake for Channel B
analogWrite(11, 175); //Spins the motor on Channel B
delay(1000);
digitalWrite(9, HIGH); //Engage the Brake for Channel A
digitalWrite(8, HIGH); //Engage the Brake for Channel B
delay(1000);
leftDistance = ping(); //scan to the left
delay(1000);
//RETURN TO CENTER
//Motor A forward
digitalWrite(12, LOW); //Establishes backward direction of Channel A
digitalWrite(9, LOW); //Disengage the Brake for Channel A
analogWrite(3, 175); //Spins the motor on Channel A
delay(1000);
compareDistance();
}
}
void compareDistance()
{
if (leftDistance>rightDistance) //if left is less obstructed
{
digitalWrite(9, HIGH); //Engage the Brake for Channel A
digitalWrite(8, HIGH); //Engage the Brake for Channel B
delay(1000);
//Motor A backwards
digitalWrite(12, LOW); //Establishes backward direction of Channel A
digitalWrite(9, LOW); //Disengage the Brake for Channel A
analogWrite(3, 100); //Spins the motor on Channel A
delay(2000);
}
else if (rightDistance>leftDistance) //if right is less obstructed
{
digitalWrite(9, HIGH); //Engage the Brake for Channel A
digitalWrite(8, HIGH); //Engage the Brake for Channel B
delay(1000);
//Motor B backwards
digitalWrite(13, LOW); //Establishes backward direction of Channel B
digitalWrite(8, LOW); //Disengage the Brake for Channel B
analogWrite(11, 100); //Spins the motor on Channel B
delay(2000);
}
else //if they are equally obstructed
{
digitalWrite(9, HIGH); //Engage the Brake for Channel A
digitalWrite(8, HIGH); //Engage the Brake for Channel B
delay(1000);
//Motor A forward
digitalWrite(12, LOW); //Establishes backward direction of Channel A
digitalWrite(9, LOW); //Disengage the Brake for Channel A
analogWrite(3, 100); //Spins the motor on Channel A
//Motor B Forward
digitalWrite(13, HIGH); //Establishes backward direction of Channel B
digitalWrite(8, LOW); //Disengage the Brake for Channel B
analogWrite(11, 100); //Spins the motor on Channel B
delay(2000);
}
}
// establish variables for duration of the ping,
// and the distance result in inches and centimeters:
long ping()
{
// The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
// Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
pinMode(pingPin, OUTPUT);
digitalWrite(pingPin, LOW);
delayMicroseconds(2);
digitalWrite(pingPin, HIGH);
delayMicroseconds(5);
digitalWrite(pingPin, LOW);
// The same pin is used to read the signal from the PING))): a HIGH
// pulse whose duration is the time (in microseconds) from the sending
// of the ping to the reception of its echo off of an object.
pinMode(pingPin, INPUT);
duration = pulseIn(pingPin, HIGH);
// The speed of sound is 340 m/s or 29 microseconds per centimeter.
// The ping travels out and back, so to find the distance of the
// object we take half of the distance travelled.
return duration / 29 / 2;
