Easy IoT is a simplest IoT Solution presented by DFRobot

I have to admit that taking a bath can greatly help relax. And I prefer hot tubbing, no matter it’s summer or winter season. But that can be annoying when you can not estimate whether the temperature is proper. What's more, I bag most of us need a timer when you enjoy yourselves in the tub.So I decided to deal with such a BATHING COMPANION.The anime character is from RIPNDIP one of my favourite brands.
STEP 1 Design & Material Required

Material Required:
RGB LED module 5050

DFRduino Nano 3.0

# LR44 cell battery(with a case) [for independent power supply]

USB Cable

Waterproof DS18B20 Sensor Kit

some PMMA, and some wire

We need two functions :
I. A timer(cos I used to stay in bathroom for too long)
II. A temperature sensor(cos I never wanna to do any move like this :)

Solution :
I. I made a timer by Arduino IDE and use LED to hint you about time.
II. I take Waterproof DS18B20 Sensor as a “cat tail” to show if the temperature is proper.

And we need a holder to hold all these stuff.And it should be as simple as possible.

Here is a draft of the holder :

STEP 2 circuit logic & code

Code: Select all
#include <OneWire.h>
#include <RGBLED.h>

RGBLED myled = RGBLED(9,10,11);
int DS18S20_Pin = 2; //DS18S20 Signal pin on digital 2

//Temperature chip i/o
OneWire ds(DS18S20_Pin);  // on digital pin 2

int ledPin = 9;                // Connect LED on pin 9, or use the onboard one
int KEY = 3;                 // Connect Touch sensor on Digital Pin 3

void setup(){
  pinMode(ledPin, OUTPUT);      // Set ledPin to output mode
  pinMode(12, OUTPUT);
  pinMode(KEY, INPUT);       //Set touch sensor pin to input mode

void loop(){
  float temperature = getTemp();
  delay(100); //just here to slow down the output so it is easier to read
   if(temperature >= 40) {      //Read Touch sensor signal
        digitalWrite(12, LOW);
        digitalWrite(ledPin, HIGH);   // if Touch sensor is HIGH, then turn on
   else if(digitalRead(KEY)==HIGH){         //start the timer
    digitalWrite(12, LOW);
    digitalWrite(10, HIGH);
        digitalWrite(ledPin, LOW);    // if Touch sensor is LOW, then turn off the led

float getTemp(){
  //returns the temperature from one DS18S20 in DEG Celsius

  byte data[12];
  byte addr[8];

  if ( !ds.search(addr)) {
      //no more sensors on chain, reset search
      return -1000;

  if ( OneWire::crc8( addr, 7) != addr[7]) {
      Serial.println("CRC is not valid!");
      return -1000;

  if ( addr[0] != 0x10 && addr[0] != 0x28) {
      Serial.print("Device is not recognized");
      return -1000;

  ds.write(0x44,1); // start conversion, with parasite power on at the end

  byte present = ds.reset();
  ds.write(0xBE); // Read Scratchpad

  for (int i = 0; i < 9; i++) { // we need 9 bytes
    data[i] = ds.read();
  byte MSB = data[1];
  byte LSB = data[0];
  float tempRead = ((MSB << 8) | LSB); //using two's compliment
  float TemperatureSum = tempRead / 16;
  return TemperatureSum;
STEP 3 Structure

I wanted to make it as simple as possible, so I did some laser-cutting stuff.
And then screw on

STEP 4 assembling

Hint: adjust the screw to make sure the case can hold ‘the cat tail’

Check it yourself!!!