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Precautions while using a Relay module

Updated: Feb 13

In this article, we will check out the various steps and precautions to keep in mind, while working with relay modules.

Relay Module
4 Channel Relay module

Relays are basically hardware devices that allow us to control equipment over the internet.

Here we are provided with single as well as multiple channel relays. They can be controlled with limited voltages such as 5V and 3V. Here, we are using 5V, but relays that can be run using 3V are also available in the market. Vcc is connected to 5V of the Arduino board. In the relay module, we can see 3 sockets for Mains voltage and 3 sockets for low voltage as well.

There are 12 sockets which go to Vcc and ground. The controlling pins are connected to the microcontroller and we are able to see the sockets that carry high and voltages respectively. In the sockets that carry high voltage, we can mainly see that the socket terminals to control voltages. They are

1. Major relay module

2. NO which stands for Normally Open

3. NC which stands for Normally Closed.

This 3 socket mechanism is repeated in all other blocks as well.


When you are connecting a lamp to switch it ON and OFF, use NO in order to avoid the risk of burning out, and thus the wastage of energy is minimalized.

While using the relay module, make sure that it never touches the conducting parts of the module such as socket, screws, etc. while the power is being supplied.

Make sure that you never use a relay that exceeds the contact rating of the relay that is given on the blocks. You may refer to the datasheet of the module for understanding further details. When the load exceeds, there will be deterioration of the relay module which could potentially damage it.

The durability could be affected by the switching conditions. Continued application of the relay could result in damage and inefficiency of the module and later result in insulation failure.

Cross -check and verify that there is not even one incorrect wiring as it would extract the external circuit which could possibly lead to burning out.

The relay module must not be used in places that are surrounded by explosive materials or gases as it could heat up and explode. It should be tested in an appropriate atmosphere before deployment. This will give a realistic output.

The ideal working conditions to be followed are as follows:

  • Temperature: 15-35 degree centigrade

  • Humidity: 25 to 75%

  • Pressure: 86-106 Kilopascal

  • Altitude: 2000 meter (maximum)

The values of load given in the datasheet should be used so that there will not be variations in the circuit during actual implementation.

Storage and maintenance is a crucial step that many people overlook. Maintaining the relay module without it being exposed to any kind of dust or stuff is important. Prevent it from dust and moisture as it can get clogged between the device causing contact failure and a short circuit.

While selecting the relay, check the coil specifications which match with the design of the circuit; else it may result in low performance and circuit burnout.

Keep in mind the switching capacity and graphs shown in the datasheet for durability and selection.

The contacts kept open or close have a great impact on the relay module's functionality. The greater the amount of contact exhaustion, the more the chances of malfunction.

Electrical durability, type of load, and ambient atmosphere are some of the most important factors to be taken into consideration while using a relay module.

The rating selected should preferably lower end; it is safe to use the lower end of ratings as higher-end might cause burning out.


The relay if stored for so much time in high heat and other least preferred conditions will lead to oxidation films forming on the equipment which can result in contact failure and rusting.

There are possibilities for the formation of green corrosive material on top of the module in conditions of high humidity.

The relay should not exceed the normal shock of vibration rates to prevent deformation of the equipment.

The relay should not be used in places where there is a presence of an external magnetic field of intensity 800A/m or more as it will surely lead to malfunction.

The wires should be properly soldered and twisted. If not taken care of, it may lead to disconnection. Care must be taken to not connect to tap terminals and keep all the screws tight.

There could be possibilities of relay exceeding the voltage range and the component might catch fire. For this, use a protection circuit with transistors, screws, and specified hardware.

Video by: Sai Parimal

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Anushka Gupta
Anushka Gupta

Hats off to Learn Electronics India for crafting such an informative and user-friendly blog on relay module precautions! As someone who is just beginning to dabble in electronics, this article was exactly what I needed. The explanations were clear, concise, and most importantly, actionable. I feel more confident in using relay modules now, all thanks to the valuable insights provided by this blog. I can't thank you enough for sharing your expertise with the community. I'm eagerly looking forward to more engaging content from Learn Electronics India.


Short and effective! LearnElectronics India never disappoints.

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