Automatic Water Heating System 2.0

Introduction: Automatic Water Heating System 2.0

This is the modification of my old version. This is a technology in small box. In the previous version there is no possibility of adjusting the temperature that we need. It had only 2 temperature setup. In this version I added temperature adjustment using rotary encoder and also added a display. Also changed the micro controller to Arduino pro mini. This system has a buzzer i.e., when the water is heated buzzer starts to sound. It has an amazing feature that is last memory. When we set a temperature, that is saved in the EEPROM and when restarted the previous temperature is loaded and it will be cut-off at that temperature. We can use as normal water heater without the control of this system by using a separate slide switch(Auto/Manual).

Some people said to me, it is better to buy a geyser which is very costly comparing to my project. In my system I can use different brands of immersion water heater and we can put where ever we want and also low cost and handy.

Visit my Temperature Controlled Water Heater 1.0.

Step 1: Materials Needed

Plastic case

USB mobile charger

Rotary encoder


Arduino pro mini

5v Relay module



AC Socket

Temperature sensor


10k SMT resistor

4.7k resistor

1k resistor

3-pin Mains cord

SPDT Slide switch

Immersion Water Heater

Step 2: Charger

Disassemble the charger and remove the PCB. Solder wire for 220v input and 5v output.

Step 3: Rotary Encoder

Solder 10k resistor to the board which is used for the push button. Cut the stem in required height for inserting the knob. Since it is not possible to screw fit, I super glued some scrap wood.

Step 4: Enclosure

Cut holes for inserting the electronics

Step 5: Install Electronics

Install all the electronics

Step 6: Wiring

Wire according to the given picture.

Step 7: Water Heater

Take an aluminium strip, bend and drill holes as shown in pictures. Attach that bracket to the immersion water heater so as to fit the temperature sensor and secure the wire with zip tie.

Note: Since the temperature sensor is fitted very near to heating element, temperature raises very fast and the heater will be shutdown. Immediately heat is spread and temperature goes down and heater will be switch ON. This will happen very fast for 3 times until the preset temperature reaches. After 3 buzzers, hot water will be ready. There are two ways to rectify this problem. One is placing the sensor away from the heating element. Second is to change the code. I provided the code in next step separately.(Please note that I have not tested the rectification code). I am sure it will work. I attached the heating element to water heater to make it as a single unit.

Step 8: Code

I modified the Adafruit SSD 1306 example for the display purpose. Lot of modifications made to the previous temperature code. I used EEPROM library for last memory. Onewire library for the temperature sensor.

Rectification code:

int count=0; // take it as global variable

void buzzer() // replace the original method




for(int i=0;i<5;i++)


digitalWrite(buzzerpin, HIGH);


digitalWrite(buzzerpin, LOW);





Step 9: Labelling

I used epson photo paper.

Step 10: Testing

When the device is turned ON, startup screen appears and then heating starts with reference to the EEPROM temperature set (That is set previously). When turned ON for first time we have to set down the temperature because the default temp is above 100 c. To change the temperature click the button of rotary encoder. Set the temperature and click the button once again to start heating. After the heating is completed screen displays "completed".



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    19 Discussions

    Sir were having a trouble. if we touch the water where the water heater submerge, we feel like electricuted/grounded. Our source is Line to Line. Were from the Philippines. What is the problem sir? Thank You in advanced sir.

    Hello Sir Sandilya. Where is the updated schematic diagram? We need it badly Sir, because we do not know where to put the positive and negative end of the buzzer. Thank You in Advance Sir.

    3 replies

    I would like to see your version of water heater. After completion please upload image.

    Where is the connection of the buzzer in the schematic diagram?

    1 reply

    Buzzer is connected to Arduino pin 9. Thanks for letting me know. I will update the schematics.

    Our arduino pro mini doesn't work and we couldn't upload codes. we even followed the connection in the picture above. we can barely find out the problem

    1 reply

    Before uploading the code remove all the connections from arduino pro mini. Then it works.

    Does the connection and codes are the same?

    1 reply

    All the connections are same. While uploading the sketch in arduino IDE, you have to change the microcontroller to atmega 328.

    Sir, can we use the Arduino atmega328 as substitute of Arduino Pro Mini?

    Thank You in Advance. :D

    1 reply

    Hi! i just saw your vid. and i'd like to ask what is the rated volts of the water heater? is if it 220V or 5V.

    coz im interested to do this as project.

    i would be glad for your response.


    5 replies

    Data logger means it records temperature at intervals over a period of time. This what you are asking? In my project it stores only one temperature value that we set.