Category Archives: Arduino Tutorials

Arduino relay module interface

The new KEYES 5V Relay Module is perfectly made for Arduino application. It has three pins, the VCC, GND and Signal. It can act as switch if the circuit and the load circuit have different supply voltage. It is commonly use if the load circuit is AC. It is a switch used to connect isolated connection from the circuit using a circuit signal. It has red LED that turns on every time the coil is energized or the signal pin has a high input. Commonly used in automation control circuit, it is actually a small Current to control a large current operation “automatic switch.”

Arduino Connection with Relay Module

Arduino Relay Module Interface

For the DC part of the circuit:

Arduino digital pin 10 –> module pin S
Arduino GND –> module pin –
Arduino +5V –> module pin +

AC Part of the circuit:

On the AC side connect your feed to Common (middle contact) and use NO (Normally Open) to Lamp. It will get power when (S) is high.

Warning: Always be very careful when experimenting with AC, electrical shock can result in serious injures.

Relay module from bottom side is open when AC is connected do not touch the circuit.

Arduino Program for Relay module

This program will turn on and off the Lamp. Similar to Blink example. You can see module led also blinks.

Touch Screen interfacing with Arduino

Resistive touch screen displays are composed of multiple layers that are separated by thin spaces. Pressure applied to the surface of the display by a finger or stylus causes the layers to touch, which completes electrical circuits and tells the device where the user is touching.

In this chapter we are focusing only on 4-wire resistive touch screen interfacing. Continue reading Touch Screen interfacing with Arduino

Three Wire LCD Interface with Arduino

We have seen parallel interface technique using Arduino library and we know that it requires 6 IO Lines, Now let’s see how we can reduce required IO’s using 74HC595. We know that we can reduce number IO required by using I2C based LCD interface circuit; It costs ten times more than 74HC595 Circuit.

Arduino 3 wire LCD interface circuit

            In this circuit similar to the bargraph display we are using 74HC595 Shift register to interface 16×2 LCD. Continue reading Three Wire LCD Interface with Arduino

Four Digit 7-Segment Display Interfacing with Arduino

7-segment displays are most popular in panel meters, It can show direct numerical value on display, It’s cost is low and display size bigger than LCD’s. Lets interface four digit display, most of the time four digits are enough to display data.

Problem Statement

We are making a Voltmeter using four digit 7-segment display, for this IC 74HC595 shift register is used instead of 7448 decoder, use of shift register gives few advantages such as you can display sign, few alphabets and control decimal point location. Continue reading Four Digit 7-Segment Display Interfacing with Arduino

RGB LED Interfacing with Arduino

In some cases you need to display a static text with different colors, for this purpose you can use RGB LED Strips. In this tutorial we will learn how to interface RGB LED strip with arduino and drive it using ULN2003.


This is a basic tutorial for using Common Anode RGB LED Strip, PWM, and switch. By the end, you will have single switch to control colors of the LED strip. Connect the LED’s anode lead to +12V and connect the 3 RGB cathode leads to digital pins 9, 10, 11 through ULN2003 respectively.

RGB LED Strip Pin out
RGB LED Strip Pin out

RGB LED Strip Connections with Arduino

To drive complete RGB LED Strip we have used ULN2003 as a driver circuit, LED strip works at 12V. You can combine ULN2003 driver outputs to get more current.

RGB LED Arduino Interfacing Circuit
RGB LED Arduino Interfacing Circuit

Arduino Code for RGB LED Color Control


Press switch and see that we have around ten different colors; You can change the color using SetColor(R,G,B). try different values of RGB.