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Another Arduino timer

Another little project, mostly made to learn how to use TIP102 transistors.

The setup is controller an 250 kg electromagnet (500mA@12V), and using only one TIP102 to open and close, and one small 1A 12V switch mode power supply. The power supply is connected the the Arduino's connector for an external power source, and the magnet is then driven through the VIN pin.

I also added a small piezo from a computer to make it able to beep when the timer is started and stopped.

Everything is mounted on a protoshield 4 and looks very clean (both because there aren't many components, plus no extra supply wires for the load).

I also added a "Start timer" function, where the analog pin 5 is used to determine when the timer should start. The reason for the analog pin is so it can be used for the pressure pads too, and start when enough pressure is reached. The pin is pulled up by an 10k ohm resistor, and will then be pulled towards gnd by the switch, variable resistor, pressure pad, or what else it could be.

Version 1.0

This is with the TIP102 to switch the 12V output on and off, the piezo to give some audio signal, and a blue LED to show that the TIP102 is activated.

BLAH! Hit the blue wire with my soldering iron, but didn't burn through the isolation.

Version 1.1

This got the same as version 1.0, but here I added screw terminals for the wires, and also feeding the Arduino through the VIN port, as the on-board diode on the Arduino gave up when it had to both pull the relay and the little motor I added to the TIP120. The TIP120 is connected to the PIN6 (pwm) on the Arduino.

Fun with pressure pads

Not really sure where this can be used, maybe some kind of game?

The standTime is how long (in seconds) you will have to press or stand on the pads before the task is complete.

If you want to allow some short dropdowns of pressure, you can set that in the maxRest (also in seconds) and the low pressure will then be ignored for that amount of time, and the timer will then be reset if it is exceeded.

//Define the time with pressure
int days      = 0;
int hours     = 0;
int minutes   = 0;
int seconds   = 10;

//Program starting
unsigned long standTime; //Seconds to have enough pressure on both pads
unsigned long maxRest = 3; //Seconds the minimum pressure can be bypassed without resetting the timer
int minPressure = 880; //Minimum allowed pressure on both pads

//Analog
int leftPadPin = 0; //Left pressure pad
int rightPadPin = 1; //Right pressure pad

//Digital
int piezoPin = 2; //Where the piezo is connected to
int ledPin = 13; //Just for visualisation
int relayPin = 3;

//No further editing needed
long lastSit;
long lastRest;

void beep(int val)
{
  digitalWrite(ledPin, HIGH);

  for(int i=0; i < 500; i++)
  {
    digitalWrite(piezoPin, HIGH);
    delayMicroseconds(val);
    digitalWrite(piezoPin, LOW);
    delayMicroseconds(val);
  }

  digitalWrite(ledPin, LOW);
}

void setup()
{
  standTime = (seconds*1000) + ((minutes*1000)*60) + (((hours*1000)*60)*60) + ((((hours*1000)*60)*60)*24);
  maxRest = maxRest*1000;

  //Set pin modes
  pinMode(piezoPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(relayPin, OUTPUT);

  //Turn magnet on
  digitalWrite(relayPin, HIGH);

  lastSit = millis();
  lastRest = millis();
}

void loop()
{
  if (analogRead(leftPadPin) <= minPressure || analogRead(rightPadPin) <= minPressure)
  {
    if (millis() - lastRest > maxRest && lastSit != 999999999)
    {
      //Bummer, timer just go reset
      beep(100);
      lastRest = millis();
      lastSit = millis();
    }
  }
  else
  {
    lastRest = millis();

    if (millis() - lastSit > standTime && lastSit != 999999999)
    {
      lastSit = 999999999; //Yay! You made it, lets set it high so it won't keep beeping

      //Switch magnet off
      digitalWrite(relayPin, LOW);

      for(int i=0; i < 4; i++)
      {
        beep(200);
        delay(100);
      }
    }
  }
}

Piezo

This was a fun little thing to try.

All it required was an old piezo from a computer case, an arduino and a few lines of code. This little code only makes a beep every second, where the pitch can be adjusted by changing "val = 130" up or down. Changing it up will result in a deeper noise because it defines the delay between high and low.

int piezoPin = 11;

void beep()
{
  for(int i=0; i < 500; i++)
  {
    int val = 130;
    digitalWrite(piezoPin, HIGH);
    delayMicroseconds(val);
    digitalWrite(piezoPin, LOW);
    delayMicroseconds(val);
  }
}

void setup()
{
  pinMode(piezoPin, OUTPUT);
}

void loop()
{
  beep();
  delay(1000);
}