/*
  Forum: https://forum.arduino.cc/t/chair-occupancy-light-switch/1215354
  Wokwi: https://wokwi.com/projects/387817499677410305

*/
// from arduino forum  https://forum.arduino.cc/t/pressure-sensor/546144/4
// using sensor that looks like mine

const byte switchPin = 2;  // connect the switch to pin 2, the other side to ground
const byte ledPin = 13;  // use the built-in LED as an indicator
const byte LightsPin = 3; // this pin sends signal to Mosfet to turn on lights
byte SwitchRead; // variable to store value of the Seat Occupancy Switch

void setup() {
  pinMode(switchPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
  pinMode(LightsPin, OUTPUT);
  Serial.begin(9600);  
}

void loop() {
  // The byte variable SwitchRead is set to HIGH or LOW depending
  // on the state read by the function digitalRead(switchPin).
  // The exclamation mark (!) in front of a (usually boolean) variable 
  // is inverting the result of digitalRead(). If the result was HIGH it becomes LOW
  // or vice versa. 
  // As switchPin has been set to pinMode INPUT_PULLUP the return of digitalRead()
  // will be HIGH if the button is not pressed (the switch is open) as an internal pullup
  // resistor keeps the input state on HIGH level. 
  // If the button is pressed, switchPin is connected to GND. This draws the state 
  // to LOW. 
  // To make sure that the Led and the Light are switched OFF when the button is 
  // not pressed, the state has to be inverted:
  // 
  //  See this table of states
  //
  //    Switch                 Switch state        Light state
  //  -----------------------------------------------------------------
  //    not pressed              HIGH                   LOW
  //    pressed                  LOW                    HIGH 
  //
  //
  // As loop() loops really quick (not to say damned quick) it is sufficient to
  // read the switch state once per loop and use the variable to set ledPin
  // and LightsPin.

  SwitchRead = !digitalRead(switchPin);

  digitalWrite(ledPin, SwitchRead );
  digitalWrite(LightsPin, SwitchRead );
  Serial.println(SwitchRead);
}