This is a device that warns and sets off an alarm when you've been sitting on your chair for too long, reminding you to get off of your @$$ and get some exercise! It's the Pomodoro Clock of Chairs, one chair to rule them all!

Working as a software developer as a day job means I am almost always glued to a chair. Many older people suffer from back problems due to the nature of the job. I have created a mechanism that may circumvent this problem by detecting how long you've been sitting on a chair and sounding an alarm if you have been there for too long!

Step 1: BoM

* Photosensor

* 10kΩ Resistor

* Jumper Cables

* Arduino

Tools:

* Soldering Iron

Step 2: Solder

Since I wanted to go breadboard-less we'd need to solder the resistor onto one of the pins of the photosensor (call this pin 1) since the photosensor will use a voltage divider to relay input signals to the Arduino.

Step 3: Connections

Follow the table below for the connections between the I/Os and the

I/O	I/O pin	Arduino Pin
Photosensor	1	A0
Photosensor	2	GND**
Buzzer*	1	9
Buzzer*	2	GND**

* Order of pins do not matter for the buzzer

** The Arduino board has at least 3 GND pins

Step 4: Code

/**

 * 'Get out of your chair alarm!'
 * By TechMartian
 *

/cosntants for the pins where sensors are plugged into.
const int sensorPin = 0;
const int buzzPin = 9;

unsigned long minute1; 
float time1;

//Set up some global variables for the light level an initial value.
int bright;  // initial value
int lightVal;   // light reading

void setup()
{
  // We'll set up the LED pin to be an output.
  bright = 900;
  //we will take a single reading from the light sensor and store it in the lightCal        //variable. This will give us a prelinary value to compare against in the loop
}

void loop()
{

  lightVal = analogRead(sensorPin); // read the current light levels

  //if lightVal is less than our initial reading withing a threshold then it is dark.
  if(lightVal <  bright)
  {
      // reset the timer, person began to sit down
      minute1 = minute();
  }  else   // otherwise it's bright
  {
      hour1 = -1;
      minute1 = -1;
  }
  unsigned long minute = minute();
  if (abs(60 - minute + minute1 )>20){
    // time to stand up
    while (lightVal <  bright) {  // still sitting
    tone (buzzPin, 1000, 100);
    delay (100);
    noTone(buzzPin);  }
  }