Week 13_Output devices

For this assignement I studied how to use a Peltier cell.
Effectively, Peltier cell's going to be the most important Output devices in my Final project.
Peltier cell's based on the Thermoelectric effect wich (as you can read in this Wiki) is the direct conversion of temperature differences to electric voltage and vice versa.
This devices will be useful in my final project cause I need to let my developing chemicals at constant temperature.
Here I found a useful APPLICATION NOTE with TECHNICAL DATA.

Testing

By the first I bought one 12v cell 3x3cm and I started understand how many Ampere it required.
Data I collected says that with 5v it takes around 1A, with 12v takes 1,6A and it dies at 15v.
Than I bought a new one. :D

Board design

Than I prototype kind of circuit based on arduino1 to understand how to use the peltier cell with the Thermistor and let the temp of some liquid be constant.

Between the others I use a L298 Multiwatt15 (here the datasheet) in order to control the 12v cell and to simply invert its polarity.

Here you can see Arduino code to use the Thermistor plus the Cell through the l298m.

 #define IN1 8
#define IN2 9

void setup() {
  pinMode(IN1, OUTPUT);
  pinMode(IN2, OUTPUT);
  Serial.begin(9600);

}
int tempV = 18;

float correzione(int t) {
  float tt;
  tt = 46 - t / 10;
}
void raffredda() {
  digitalWrite(IN1, HIGH);
  digitalWrite(IN2, LOW);
}

void riscalda() {
  digitalWrite(IN1, LOW);
  digitalWrite(IN2, HIGH);
}

double Thermister(int RawADC) {
  double Temp;
  Temp = 46 + RawADC / 10 * (-1);
  return Temp;
}

float tempCorretta;
void loop() {
  tempCorretta = Thermister(analogRead(A2));
  if (tempCorretta > tempV) {
    raffredda();
  }
  else {
    riscalda();
  }
  Serial.println(tempCorretta);
} 

And here (download source files) the schematic of the board.

Milling and soldering

Using the same board of the input assigmement (and the same I'll use for my final project) I add the peltier cell with an HeatSink and the l298n.

It Works!!