Trouble using proximity sensor as input and LED output

Question

I was wondering if anyone had any pointers or advice to make this project work. Essentially I would like to have the LED fade (meaning like fade on and off at a calm rate) at one rate when there is nothing close to the proximity sensor, and then to speed up the fade amount when there is something close to the sensor.

#include <NewPing.h>   //include the library

int led = 9;           // the PWM pin the LED is attached to
int brightness = 0;    // how bright the LED is
int fadeAmount;    // how many points to fade the LED by

int triggerPin = 12;   //pin conneccted to the Trig pin on the sensor
int echoPin = 11;       //pin connected to the Echo pin on the sensor
int maxDistance = 200;  //set the max distance for the sensor to read (helps with errors)
int distanceVal;        //variable to hold the distance val

int sampleRate = 200;   //how fast to sample the value
long lastReading;       //used for the timer

NewPing proximity1(triggerPin, echoPin, maxDistance);   //sets up the sensor object

void setup() 
{
  Serial.begin(9600);  //start the serial port
  pinMode(led, OUTPUT);
}

void loop() {

    if(millis()-lastReading>=sampleRate) //this very simple statement is the timer,
  { 
  distanceVal = proximity1.ping_cm();  //get the distance value in centimeters


  lastReading = millis();

  Serial.print("Distance Reading CM : ");  //print the value to the Serial monitor
  Serial.println(distanceVal);


if(distanceVal<20){

fadeAmount = 5;
}
else{
  fadeAmount = 2;
}

  // set the brightness of pin 9:
  analogWrite(led, brightness);

  // change the brightness for next time through the loop:
  brightness = brightness + fadeAmount;

  // reverse the direction of the fading at the ends of the fade:
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
  // wait for 30 milliseconds to see the dimming effect
  delay(30);
  }
}

https://github.com/sanaalla/Fade-LED-with-Proximity-sensor

Above is my code, which is not working. I am fairly new to Arduino and so would greatly appreciate some more seasoned wisdom!

Answer 1

You want 2 independant loops, one for the measurement and one for the dimming effect. The latter one must also be able to run when not measuring.

if(millis()-lastReading>=sampleRate) //this very simple statement is the timer,
{ 
  distanceVal = proximity1.ping_cm();  //get the distance value in centimeters


  lastReading = millis();

  Serial.print("Distance Reading CM : ");  //print the value to the Serial monitor
  Serial.println(distanceVal);
}

if(millis() - lastFade >= fadeRate) //other timer
{
  lastFade = millis();
  if(distanceVal<20){
    fadeAmount = 5;
  }else{
    fadeAmount = 2;
  }

  // set the brightness of pin 9:
  analogWrite(led, brightness);

  // change the brightness for next time through the loop:
  brightness = brightness + fadeAmount;

  // reverse the direction of the fading at the ends of the fade:
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
}

Answer 2

*update! I fixed the code and got it to do what I want.

#include <NewPing.h>   //include the library

int led = 9;           // the PWM pin the LED is attached to
int brightness = 0;    // how bright the LED is
int fadeAmount1 = 10;    // how many points to fade the LED by
int fadeAmount2 = 2;    // how many points to fade the LED by


int triggerPin = 12;   //pin conneccted to the Trig pin on the sensor
int echoPin = 11;       //pin connected to the Echo pin on the sensor
int maxDistance = 200;  //set the max distance for the sensor to read (helps with errors)
int distanceVal; //variable to hold the distance val
int lastFade;
int fadeRate = 200;

int sampleRate = 200;   //how fast to sample the value
long lastReading;       //used for the timer

NewPing proximity1(triggerPin, echoPin, maxDistance);   //sets up the sensor object

void setup() 
{
  Serial.begin(9600);  //start the serial port
  pinMode(led, OUTPUT);
}

void loop() {

  if(millis()-lastReading>=sampleRate) //this very simple statement is the timer,
{ 
  distanceVal = proximity1.ping_cm();  //get the distance value in centimeters


  lastReading = millis();

  Serial.print("Distance Reading CM : ");  //print the value to the Serial monitor
  Serial.println(distanceVal);
}


if(distanceVal<20){

    // set the brightness of pin 9:
  analogWrite(led, brightness);

  // change the brightness for next time through the loop:
  brightness = brightness + fadeAmount1;

  // reverse the direction of the fading at the ends of the fade:
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount1 = -fadeAmount1;
  }
  // wait for 30 milliseconds to see the dimming effect
  delay(30);
}


else{

    // set the brightness of pin 9:
  analogWrite(led, brightness);

  // change the brightness for next time through the loop:
  brightness = brightness + fadeAmount2;

  // reverse the direction of the fading at the ends of the fade:
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount2 = -fadeAmount2;
  }
  // wait for 30 milliseconds to see the dimming effect
  delay(30);
}


}