Programing the robot to use the light sensor to avoid light

Arduino → Arduino Tutorials and Guided Projects → VEX + Arduino, Mobile Robotics Platform → Programing the robot to use the light sensor to avoid light

Say you wanted your robot to avoid light - perhaps your robot's photosensory is photosensitive, or you want to hunt vampires. We can do this by a small modification of the previous program, and get drastically different results. This is one of the powers of programming - once you have a solid code base, you can easily manipulate it to get a variety of interesting results.

All we need to do is change the code so that shadeDiff is subtracted from the rightServo, and added to the leftServo.

#pragma config(CircuitBoardType, typeCktBoardUNO) #pragma config(UART_Usage, UART0, uartSystemCommPort, baudRate200000, IOPins, dgtl1, dgtl0) #pragma config(Sensor, anlg0, rightLight, sensorReflection) #pragma config(Sensor, anlg1, leftLight, sensorReflection) #pragma config(Sensor, dgtl2, button, sensorTouch) #pragma config(Motor, servo_10, rightServo, tmotorServoContinuousRotation, openLoop, reversed, IOPins, dgtl10, None) #pragma config(Motor, motor_11, leftServo, tmotorServoContinuousRotation, openLoop, IOPins, dgtl11, None) //*!!Code automatically generated by 'ROBOTC' configuration wizard  !!*//   task main() { int leftValue = 0; int rightValue = 0;   int leftLow = 1000; //Arbitrary high numberso the < comparison will work (we don't want the low value to always be 0!) int rightLow = 1000; //Same deal here. int leftHigh = 0; int rightHigh = 0;   // Auto-calibration ended by button press. The button will begin the light following. while(!SensorValue[button]) { leftValue = SensorValue[leftLight]; rightValue = SensorValue[rightLight];   //Get low and high values for the left sensor if(leftValue > leftHigh) { leftHigh = leftValue; } else if(leftValue < leftLow) { leftLow = leftValue; }   //Get low and high values for the right sensor if(rightValue > rightHigh) { rightHigh = rightValue; } else if(rightValue < rightLow) { rightLow = rightValue; } }   int factor = 8; //This value worked for us however you might want to change it for your robot/flashlight intensity.   // Light following loop while(true) { //Maps both sensors to a scale of 0-20. 20 was chosen so the calculation doesn't overflow (use a number larger than 16 bits) leftValue = (SensorValue[leftLight] - leftLow) * 20 / (leftHigh - leftLow); rightValue = (SensorValue[rightLight] - rightLow) * 20 / (rightHigh - rightLow);   //Find the difference in light values int shadeDiff = (leftValue - rightValue);   //Run the motors motor[leftServo] = 40 + (shadeDiff * factor); motor[rightServo] = 40 - (shadeDiff * factor);   //If the loop cycles too quickly, we get calculation errors. Therefore we regulate the speed by waiting a bit. wait1Msec(10); } }