Arduino Projects

How to make Automatic Water Tap using Arduino and Solenoid Valve

Automatic Water Tap


This tutorial is based on the Automatic Water Tap control system using Arduino Uno or Mega, 12-volt Solenoid Valve, Infrared Sensor and a 12-volt SPDT type relay. The main purpose of this project is to stop wasting water. The flow of water is controlled automatically using the IR “Infrared Sensor”. When the infrared Sensor detects the hand the solenoid value is Turned ON, while in the absence of the hand the solenoid valve is turned off.

The Automatic water tap control system project can be used in Colleges, homes, Universities, buildings, etc. If this project is implemented everywhere the water problem can be solved, as there will be no wastage of water.

This Tutorial covers the following.

  1. What is a Solenoid Valve?
  2. How to find the resistance of the solenoid valve coil
  3. How to perform the relay driver circuit design calculations.
  4. Finally testing the whole project.

The purchase links of the Automatic Water Tap are given below:

solenoid valve:
Arduino Uno:
Mega 2560:
lm7805 Voltage Regulator:
330-ohm resistors pack:
female DC power jack socket:
470uf capacitors:
5×7 cm Vero board:
female headers:
connection wires:
Super Starter kit for Beginners:
Jumper Wires:
Bread Board:
12v Adaptor:
PCB plate:
Variable Supply:
Digital Multimeter:
Vero Board / stripboard:
Soldering iron kit: “best” You guys should definitely purchase this:
Solder wire:
Wire Stripper:
PCB small portable drill machine:


Please Note: these are affiliate links. I may make a commission if you buy the components through these links. I would appreciate your support in this way!

What is a Solenoid Valve?

Automatic Water Tap

A Solenoid valve is basically an Automatic Valve which is electrically operated and thus removes the need for an Operator or an engineer or any other person to operate this valve manually. Regardless of the type and size of the Solenoid valve, the basic working principle of all the solenoid valves is exactly the same. The difference can be in terms of Voltage and the coil current needed to energize the coil of the solenoid valve.

In the Market, we have two types of solenoid valves

  1. Normally Open type Solenoid Valve
  2. Normally Closed type Solenoid Valve.

In Normally open type Solenoid Valve, the valve opening is open by default and when the voltage is applied the valve shut down. While in the normally closed type Solenoid Valve, the Valve opening is closed by default. When the voltage is applied the valve is opened. So by applying the voltage the state of the Solenoid valve can be changed from Open to Close or from Close to Open.

The type of solenoid valve as you can see is the Normally closed type, while in the market normally open type solenoid valves are also available. The normally closed type solenoid valve gets open when powered up.

Automatic Water Tap

As you can see it has two terminals, Its basic working principle is just like a relay, as in the case of a relay when we connect GND and 12v  as you know there are power supply coil pins in relay the relay operates similarly solenoid valve has also two coil pins and when these terminals are connected with GND and 12 volts the solenoid valve can be operated and thus can be turned ON or Turned Off depending on the type of the Solenoid Valve.

for automatically controlling the solenoid valve we will need to make a driver circuit for this. we can control this solenoid valve using a transistor, A relay, A MOSFET, etc. you can select the transistor relay or MOSFET, etc its depends on the solenoid valve coil current, which is needed to energize the solenoid valve coil.

Automatic Water Tap

first of all, we find the coil resistance, for this use a digital multimeter, set it on resistance and connect one test lead of the digital multimeter with one terminal and another test lead with another terminal. we know that solenoid valve needs 12v but the coil resistance is15.6 ohm’s.

so v = 12v

now using the Ohm’s law

v = I R

we can find the current

I = V / R

so i = 12 / 15.6

i = .769 Amps

which is equals to 769 mA.

so from this value now you can decide, whether we need to use a transistor,  MOSFET or a relay. we can use any of these three to control this solenoid valve. if you want to use a transistor or a MOSFET, make sure that the collector current or Drain current is greater than 769mA. keeping in mind the ambient temperature and other factors select a transistor or MOSFET higher than this value. but I will be using a relay. because it’s cheap and has no heat losses and another advantage of using a relay is that, it provides isolation.

Automatic Water Tap

This is a 12v SPDT type relay. SPDT stands for single pole double throw from Arduino or any other controller you can not be controlled 12v relay directly. A 12-volt relay driver will need to control the circuit. form driver circuit we can control the relay throughs 5v signal. we can make a driver circuit only if we know about its coil pins, so first, let’s find the coil pins and then find the resistance.

r = .426K ohm

r = 426 ohms

voltage is already know

Voltage V  = 12v  as the relay I am using is a 12v relay

then using the Ohm’s law

V = I R

we can find the current

I = V / R

i = 12 / 426

i = .028 Amps

which is equal to 28mA.

now we can use any NPN or PNP type transistor so far its collector current is greater than 28ma.

in the 2n2222 NPN transistor datasheet you will find that its collector current is much higher than the relay coil current. that’s why I selected the 2n2222n NPN transistor and that’s the reason I always use the 2n2222 NPN transistor for controlling the relays.

Automatic Water Tap Circuit Diagram:

Automatic Water Tap

This is the complete connection diagram, designed in cadsoft eagle As you can see one side of the relay coil is connected with 12v and the other side of the relay is connected to the collector of the 2n2222 transistor and the emitter of the 2n2222 transistor is connected with GND.  with the help of this transistor, the gnd is connected and disconnected to the relay As it’s a BJT “bipolar junction transistor” and is a current-controlled device for that’s a 10k resistor is connected at the base of the 2n2222 transistor and will be connected with pin13 of the Arduino. for controlling the relay pin 13 of the Arduino will be used

common and normally open contacts of the relay is connected to the solenoid valve A GND from dc power jack is connected with one terminal of the solenoid valve, and the other terminal of the solenoid valve is connected with common of the 12v is connected with the normally open contact of the relay. So turning on and off this relay, we can turn on and turn off this solenoid valve.

Automatic Water Tap Programming:

Watch Video

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button