Definitely you have noticed the Arduino Relay Modules on Ebay, Amazon like online shops or may be on some blog sites. Many obviously wonder and ask what are Arduino Relay Modules, what they do? In very short, these relay modules isolate two circuits so that we can control 230V appliances with Arduino using relay. As the matter is with live 230V connection, not 9V battery, usage must be by adults. There is no mercy with electric shock. Always use fuse like we said in fuse guide, get used with various switches and follow proper precaution while using relay. In this article, we will only explain the basics around these Arduino relay modules. Actually there are various types of relays and usage of relay is quite wider. We are remaining within the basic and around Arduino.
What Are Arduino Relay Modules, What They Do?
Relay is a device that can work analogous to switch with the benefit of isolation of circuits and easy designing of the circuits. The relays for Arduino available are solid state relays (SSR), not what those electromagnetic things we were taught in Twelfth grade. These relays have types of mounting, cars and Arduino use Chassis Mounting relays.
The solid state relays can be based on a single MOSFET or multiple MOSFETs in a paralleled array, can work well for DC loads. Arduino relays usually have two MOSFETs which are arranged back-to-back with their source pins tied together while their drain pins are connected to either side of the output.
Arduino relays no necessarily for controlling the AC peripherals. We can control DC peripherals too and below is such example, definitely better to get used :
Project: 4 Channel 5V Relay Module
Author: Scott C
Created: 7th Sept 2014
Arduino IDE: 1.0.5
Description: Explore the difference between NC and NO terminals.
Connect 5V on Arduino to VCC on Relay Module
Connect GND on Arduino to GND on Relay Module
Connect GND on Arduino to the Common Terminal (middle terminal) on Relay Module. */
#define CH1 8 // Connect Digital Pin 8 on Arduino to CH1 on Relay Module
#define CH3 7 // Connect Digital Pin 7 on Arduino to CH3 on Relay Module
#define LEDgreen 4 //Connect Digital Pin 4 on Arduino to Green LED (+ 330 ohm resistor) and then to "NO" terminal on relay module
#define LEDyellow 12 //Connect Digital Pin 12 on Arduino to Yellow LED (+ 330 ohm resistor) and then to "NC" terminal on relay module
//Setup all the Arduino Pins
//Provide power to both LEDs
//Turn OFF any power to the Relay channels
delay(2000); //Wait 2 seconds before starting sequence
digitalWrite(CH1, HIGH); //Green LED on, Yellow LED off
digitalWrite(CH1, LOW); //Yellow LED on, Green LED off
digitalWrite(CH3, HIGH); //Relay 3 switches to NO
digitalWrite(CH3,LOW); //Relay 3 switches to NC
This China company’s :
relays are commonly sold at very cheap rate for Arduino. As for their function – you can control any AC operated devices like electric bulb, motor to anything possible. Obviously their pricing makes them practical to use an Arduino project in to reality by building Arduino from the basic electronic components.
Cost of these Arduino Relay Modules are just less – starts from $1.5 and hundreds of guides with schematics and code are available all over the Internet. You can look at these two detailed guides for understanding the usage, circuit with Arduino relay module :