int potPin = A5;
int potRead = 0;
int ledPin = D2;
int ledBright = 0;

void setup() {
    pinMode(ledPin, OUTPUT);
    Particle.variable("pot", potRead);
}

void loop() {
    potRead = analogRead(potPin);
    // change the range of potRead
    ledBright = map(potRead, 0, 4095, 0, 255);
    analogWrite(ledPin, ledBright);
}