Peltier element

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by Jaime Patarroyo

Introduction

When a peltier element is plugged, one side starts to heat and the other starts to cool. When current flows through two dissimilar conductors heat is transferred from one side to the other. This type of actuator is commonly used in fridges and other cooling devices.

Peltier elements are commonly marked with some technical data presented in the form of TEC1-12709. Here, were only going to pay attention to the last two numbers that refer to the amount of current the peltier element needs to operate. In this example 9 amperes are needed.

Usually, peltier elements use much more current than the one that can be supply by a Wiring board connected to a USB port. This means that if you connect the actuator directly to the board it is going to get to much current and the Wiring is not going to work properly.

There are two ways of getting over this issue, first you can search for a power supply with female, center positive connector that can supply the amount of current needed. Or you can use a Mosfet Switch, a TRIAC Optocoupler, a Relay or a general purpose optocoupler (4N35) like the one used in the example beneath.

For additional information about peltier elements check this link.


Setup diagram

PeltierElement.jpg


Code

/**
 * Peltier element
 * by Jaime Patarroyo
 *
 * turns on and off a peltier element with the help of
 * an optocoupler 4N35 connected to digital pin 8, with
 * intervals of 10 seconds (10000 milliseconds).
 * 
 */

int peltierPin = 8;  // Optocoupler anode pin connected to digital pin 8.

void setup()
{
  pinMode(peltierPin, OUTPUT);      // Sets the digital pin as output.
}

void loop()
{
  digitalWrite(peltierPin, HIGH);   // Connects the optocoupler and
                                    // turns on the peltier element.
                                    
  delay(10000);                     // Waits for 10 seconds.
  
  digitalWrite(peltierPin, LOW);    // Disconnects the optocoupler and
                                    // turns off the peltier element.
                                    
  delay(10000);                     // Waits for 10 seconds.
}
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