Team Duplicity:

•

Kj Dix

Published April 21, 2019 © GPL3+

The Hot Box

A portable oven cheaper than anything you can find!

IntermediateFull instructions provided10 hours727

Things used in this project

Hardware components

Seeed Studio Grove Starter Kit for LaunchPad

7 Segment LED Display, InfoVue

4x LED screen in Grove kit

DHT11 Temperature & Humidity Sensor (4 pins)

Slide Switch

Rotary potentiometer (generic)

Texas Instruments EK-TM4C123GXL TM4C Tiva LaunchPad

Seeed Studio Grove - Relay

Software apps and online services

Arduino IDE

Story

What's the inspiration?

Our project idea was born of the need for a way to heat your food on the go. Since conventional ovens and microwaves are much to large to be casually carried around, we saw fit to create a heating device that was portable.

What can it do?

The user can adjust the potentiometer to set the temperature they want The Hot Box to achieve. The setting temperature will be visible at the left two digits of th LCD screen. The maximum temperature it can go is about 95C, which is enough to bake most cake batters and is well above the temperature most people would heat food to. The heating process takes less than 10 minutes, depending on the termperature settings. We can hold the temperature to within a degree of the set temperature, making it well-suited for those foods that need precise temperature control.

How does it work?

The way that our project works is actually quite simple. Inside a closed box we have a temperature sensor and a heating coil. When the temperature reading indicates that the box is colder or warmer than a set temperature, a relay turns the coil either on or off in order to hold the temperature of the box at a set temperature. The set temperature is controlled by a potentiometer and the set value as well as the actual measured temperature. The enclosure and box are both made of acrylic sheet and a computer power supply provides the power for both the micro-controller and the heating coil.

Fig 1: An overhead view of The Hot Box

What is the most significant challenge we meet?

With the limitation of 5V going through the relay, the heating efficiency on the coil is very low on our very first version of The Hot Box. It tooks way to long to heat up any space and can hardly hold temperature above 50C. With the power supply we decide that we need almost 10A for the coil to head up efficiently, but there is hardly any converter that handles that amount of current. In the most desparate moment, our hero KJ discovered a power-supply for a computer (the big black thing inside the larger box), and he creatively rewired the power-supply to make it suitable for our project. We later shrink the size of the temperature-controlled box so that it hits an astonishingly high temperature of 95C in a surprisingly short amount of time of 5-10 minutes.

Schematics

Code

Control code for The Hot Box

#include "DHT.h"
#include "TM1637.h"

// Constants are defined here
#define CLK 39
#define DIO 38
#define ROTARY_ANGLE_P 24
#define TEMP_HUMID_P 25
#define RELAY_PIN 37
#define TEMP_MIN 10
#define TEMP_MAX 95

volatile int rotary_input = 0;
volatile float now_setting = 0;
volatile int now_temperature = 0;
int8_t s_bits[2] = {0};
int8_t n_bits[2] = {0};

DHT dht(TEMP_HUMID_P, DHT22);
TM1637 tm1637(CLK, DIO);

void setup() {
  // Pin setup
  pinMode(ROTARY_ANGLE_P, INPUT);
  pinMode(TEMP_HUMID_P, INPUT);
  pinMode(RELAY_PIN, OUTPUT);
  // Class initializations
  dht.begin();
  tm1637.init();
  tm1637.set(BRIGHT_TYPICAL);
  tm1637.point(POINT_ON);
}

void loop() {
  // Read temperature setting from the potentiometer
  rotary_input = 4096-analogRead(ROTARY_ANGLE_P);
  now_setting = TEMP_MIN+(((float)rotary_input * ((TEMP_MAX+1)-TEMP_MIN)) / 4096);
  // Read actual temperature from the temperature-humidity sensor
  now_temperature = dht.readTemperature();
  // Turn switch on and off based on whether actual termperature is higher or
  // lower than setting termperature
  if (now_temperature < now_setting)
  {
   digitalWrite(RELAY_PIN, HIGH);
  } else if (now_temperature > now_setting )
  {
   digitalWrite(RELAY_PIN, LOW);
  }
  // Display setting and current temperature on the display
  s_bits[0] = (int)now_setting % 10;
  now_setting /= 10;
  s_bits[1] = (int)now_setting % 10;

  n_bits[0] = (int)now_temperature % 10;
  now_temperature /= 10;
  n_bits[1] = (int)now_temperature % 10;

  tm1637.display(1, s_bits[0]);
  tm1637.display(0, s_bits[1]);

  tm1637.display(3, n_bits[0]);
  tm1637.display(2, n_bits[1]);
  delay(1000);
}

Credits

Boyuan Deng

2 projects • 0 followers

Contact

The Hot Box

Things used in this project

Hardware components

Software apps and online services

Story

What's the inspiration?

What can it do?

How does it work?

What is the most significant challenge we meet?

Custom parts and enclosures

3-D model for big box

3-D model for small box

Schematics

The Hot Box Schematic

Code

Control code for The Hot Box

Credits

Boyuan Deng

Kj Dix

Comments

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The Hot Box

The Hot Box

Things used in this project

Hardware components

Software apps and online services

Story

What's the inspiration?

What can it do?

How does it work?

What is the most significant challenge we meet?

Custom parts and enclosures

3-D model for big box

3-D model for small box

Schematics

The Hot Box Schematic

Code

Control code for The Hot Box

Credits

Boyuan Deng

Kj Dix

Comments

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