Coding force sensitive resistor to give output based on time used?

Question

I have a basic set up of having a force sensitive resistor being used to power an LED as can be seen below. I am wondering how I can code it so that the LED is lit after a pressure has been applied to the FSR for a specified amount of time. Leading on from that I would like to use an RBG LED and have it so that after specified intervals on continuous pressure the LED changes colour. Any advice would be greatly appreciated.

//Constants:
const int ledPin = 3;     //pin 3 has PWM funtion
const int sensorPin = A0; //pin A0 to read analog input

//Variables:
int value; //save analog value


void setup(){

  pinMode(ledPin, OUTPUT);  //Set pin 3 as 'output' 
  Serial.begin(9600);       //Begin serial communication

}

void loop(){

  value = analogRead(sensorPin);       //Read and save analog value from potentiometer
  Serial.println(value);               //Print value
  value = map(value, 0, 1023, 0, 255); //Map value 0-1023 to 0-255 (PWM)
  analogWrite(ledPin, value);          //Send PWM value to led
  delay(100);                          //Small delay

}

Answer 1

You'll need to declare a variable to hold the start time (millis()) of when the force has exceeded the threshold.

You'll need to declare a constant to hold the threshold value (with analog data, you likely don't want to have your pressure threshold be "anything greater than 0", because noise and other things like small vibrations will trigger.

Also declare a constant to hold your "hold-off time" in milliseconds.

In your loop(), when you have an analog value that exceeds the pressure threshold, store the value of millis(). Also in your loop(), when the current millis() minus the start value is greater than the "hold-off time", activate your LED.

For RGB, same setup, but you can set your color based on how much greater the time difference is than the hold-off time.