IoT and Relay: Hardware Components Part-2

In this blog, you will learn how hardware’s like relay and bluetooth are used for IoT using Arduino. Let us tell you about the relay module in detail.


you must read our previous blog- Internet of Things using Arduino Part-1 (Introduction)

A 5 volt 10 ampere 2 channel relay interface board. The main functions of relays are to control various appliances and other equipment with large current.

Relays can be controlled directly with 3.5 volt or 5 volt logic signals from a microcontroller.

It has a 1 * 4 pin header for connecting power 5 volt and 0 volt for controlling the relays.

Pin configuration of relay

Let us understand the pin configuration.

GND stands for the connection of 0 volt to this pin IN1 which controls relay one active low relay will turn ON when this input goes below about 2.0 volt. IN2 controls relay to active low. Relay will return on when this input goes below 2 0 volt.

And the last one, VCC which is used to connect 5 volt to this pin.

And it used to power the auto couplers. There is a second 1*3 pin header for supplying the relay side on the board with 5 volt.

A jumper is present on this header selecting the 5 volt signal from 1*4 pin header to power the relays, at delivery.

Advanced configuration of relay

Let us understand the advanced configuration.

The pins are 1*3 pin header and the VCC power to the system.

This is the 5 volt vcc supply on 1*4 pin connect.

The power supply is JD-VCC relay.

It requires a 5 volt for the relays. At delivery, a jumper is present on this and adjacent VCC pin.

The default is 5 volt relay.

JD-VCC and VCC can be sorted. GND it is connected to zero volt pin of 1*4 pin header.

If opto isolation is required an isolated 5 volt supply should be used. For normal operation, a jumper between pins 1 and 2 selects a 5 volt signal from 1*4 pin header.

There is no opto isolation, this means both the input side and relay side use the same 5 volt apply.

Features of relay for IoT

Now let us understand the feature of relay module

  • high current relay
  • AC 240 volt
  • 10 ampere and
  • DC 30 volt 10 A
  • and an indication LED for relay output status.

It works with logic level signal from 3.3V to 5V devices.

It is the standard interface that can be controlled directly by the microcontroller.

Parts of relay and IoT

Here it comes the main part of relay. What is NC-COM and NO-IN relay?

COM is a common connection.

It is the central terminal. It is usually hot as power to the load is connected at this terminal.

NO is a normally open connection.

It acts like a switch.

There will be no contact between COM and NO, as it is open. When we trigger the relay module it connects to COM by the electromagnet inside the relay and supply to the load is provided with powers off the light and fan. Thus, until we trigger the state to low in relay the circuit is closed.

NC is a normally closed connection.

It is always in contact with COM. Even when really is not powered. When we trigger the relay it opens the circuit so that connection is lost.

NC behaves just opposite to NO. We are going to use a NO, normally open connection but here in this type of relay high state. In accordance of the relay low state in port turns on the relay. Now let us know about VCC. The VCC is a system power cathode. The GND is also a system power cathode. IN-1 and IN-2 is a relay control port.

This is the detailed description of all the hardware components. You can use them for home automation by learning how to code on them. And a simple way of introducing IoT at your home by relay.

Happy Reading!