Controlling a section of Adressable LEDs using an HS-SR04

Using Arduino Programming Questions
1

I'm working on a lighting project for the front of my garage. I have a string of addressable LEDs, hooked up to an Uno, being controlled by an HC-SR04 sensor, and am trying to make it so the lights will "follow" you as you walk in front of the garage. For example when you're 40 inches from the sensor the lights 40 inches away will come on, and as you move the light will "move" with you. I have it technically working, except that the lights don't always turn off as you move. I'm also wondering if there is cleaner way to code it. I've included the sketch below.

Thanks!

 #include <FastLED.h>
     
    const int trigPin = 8; //trigger for sensor
    const int echoPin = 7; //return from sensor
     
//----------LIGHT STRIP INFO----------------------------------  
    #include <FastLED.h>  
    #define NUM_LEDS 150 //number of LEDs
    #define DATA_PIN 6  //data pin
    CRGB leds[NUM_LEDS]; //light array
//**********************************************************
     
    void setup() {
      Serial.begin(9600); //starts serial monitor
      FastLED.addLeds<WS2812B, DATA_PIN, GRB>(leds, NUM_LEDS);
    }
     
    void loop()
    {
      long duration, inches; //variables for distance
//---------------------CODE TO TRIGGER SENSOR-----------------------
        pinMode(trigPin, OUTPUT);
        digitalWrite(trigPin, LOW);
        delayMicroseconds(2);
       digitalWrite(trigPin, HIGH);
       delayMicroseconds(10);
       digitalWrite(trigPin, LOW);
//******************************************************************
     
// -------------CODE TO READ,& CONVERT INPUT FROM SENSOR------------
          pinMode(echoPin, INPUT);
          duration = pulseIn(echoPin, HIGH);
     
         // convert the time into a distance
         inches = microsecondsToInches(duration);
         
          Serial.print(inches);
          Serial.print("in, ");
          Serial.println();
//*******************************************************************  

//-------CODE TO TURN ON SECTIONS OF THE LIGHTS BASED ON DISTANCE FROM SENSOR-------------
    if (inches <150)  {
      
      leds[inches-6] = CRGB(0,0,0);
      leds[inches-5] = CRGB(70,70,70);
      leds[inches-4] = CRGB(105,105,105);
      leds[inches-3] = CRGB(140,140,140);
      leds[inches-2] = CRGB(175,175,175);
      leds[inches-1] = CRGB(210,210,210);
      leds[inches] = CRGB(240,240,240);
      leds[inches+1] = CRGB(210,210,210);
      leds[inches+2] = CRGB(175,175,175);
      leds[inches+3] = CRGB(140,140,140);
      leds[inches+4] = CRGB(105,105,105);
      leds[inches+5] = CRGB(70,70,70);
      leds[inches+6] = CRGB(0,0,0);
      
      
     FastLED.show();
    }

       
    else if (inches > 150) {fill_solid( &(leds[0]), NUM_LEDS, CRGB::Black);
     FastLED.show();
    }
    delay(300);
    }
     long microsecondsToInches(long microseconds)
    {
       return microseconds / 74 / 2;
    }
2

So you've got code that sets up a certain group of leds based on the inches that you read from the sensor. And as long as that number keeps coming back only changing by 1 each time then you are turning off the ones on the ends. But if that number changes by more than 1 on any given pass then you'll leave some lights on.

Let's say inches is 50, so you're setting up 44 through 56. Next time inches is 44. So you're setting up 38 through 50. But that leaves 51 through 55 with whatever color they had before.

You need to either blank the whole strip each time before you load the new colors or keep track of what the inches value was on the last pass of loop and go back and turn off those 13 leds.

3

Delta_G:
You need to either blank the whole strip each time before you load the new colors

This is the most common way to do it. (as far as i know FastLed has a function for it)