Peltier cooler with a MOSFET module on an Arduino Uno

// Peltier cooler: an Uno runs a TEC1-12706 flat out for a minute to pull the
// cold face down, then holds it at 60 % with PWM on pin 9 through a D4184
// MOSFET module, off a 12 V battery.
//
//   9       the D4184 module's TRIG, and the Uno's GND to the module's GND
//   12 V    the battery into VIN+ and VIN-, the Peltier's red lead on OUT+
//           and its black lead on OUT-
//
// At 12 V the module draws about 6 A from a cold start and still about 4.5 A
// once it is cold, so it needs a MOSFET that is fully on from a 5 V pin (the
// D4184's AOD4184A is) and a supply that gives 6 A: a lead-acid battery or a
// 12 V 10 A adapter, not a USB port.
//
// The printed face of the module goes cold, the other face hot, and the cold
// face is only as cold as the heat sink on the hot face is good. Turn the
// heatsink setting up to 5 K/W (a bare plate) and see what happens.
//
// PWM works because the module's faces cannot heat and cool 490 times a
// second, but it is the least efficient way to run one: the heat it burns
// goes as the square of the current, so 60 % by PWM pumps less heat than
// 60 % of the voltage would. Real coolers use a buck converter.
//
// The sketch cannot read the cold face's temperature: no sensor in the
// simulator feels another part's heat. Watch the module's own readout.

const int MOSFET_PIN = 9;  // a PWM pin
const unsigned long PULL_DOWN_MS = 60000;
const int HOLD_DUTY = 153;  // 60 % of 255

bool holding = false;

void setup() {
  pinMode(MOSFET_PIN, OUTPUT);
  Serial.begin(9600);
  Serial.println("Peltier cooler: full power for a minute");
  analogWrite(MOSFET_PIN, 255);
}

void loop() {
  if (!holding && millis() >= PULL_DOWN_MS) {
    holding = true;
    analogWrite(MOSFET_PIN, HOLD_DUTY);
    Serial.println("holding at 60 %");
  }
  delay(100);
}