Once you start placing your sensor’s large distances away from your controlling microcontroller, the question of how to select a wireless module for your project often comes up. Wireless links do have several advantages over wired links in some situations.
We will be looking at the three most common types of wireless modules:
- 433MHz module
Before you ask what about bluetooth modules ? They have been left out due to cost and they are not as feature rich as some other other type of wireless modules, so I decided to leave bluetooth for another day.
Types of wireless modules
If you’ve been looking around for wireless modules to use with your electronics projects, there are generally three types that are commonly available. They operate in either the 433MHZ or 2.4GHz bands. There are other bands available but these seem to be the most common. Not getting into legalities but before you decide what module to use, you may want to check with your local communications regulator to find out what radio frequencies you are allowed to legally use for free in your country.
The first module we look at is the simplest of all of them. It operates in the 433MHz band and the communications is only one way. So if you have a sensor connected to it through a microcontroller the sensor can only transmit and you get no acknowledgement back to confirm the data has been received. There is only one available frequency channel which is 433.92MHz, so interference from other nearby devices using the same frequency like garage door openers or car remote controls may be a problem. The bit rate is also limited to about 9.6 kbps which is slow, but for periodic sensor data it would be just fine. Sending data can be as simple as inputting a single bit or you can use the microcontroller’s RS232 function to transmit large strings of data.
If you have two pairs of receivers and transmitters and were enthusiastic you could make a two way link, but there are better ways of doing that.
nRF24L01 Transceiver Module
The next module is the nRF24L01 transceiver, which is a large leap up in complexity to the 433MHz module. This module uses two way transmission using the 2.4GHz band, with bit rates up to 2Mbps. There are selectable channels between the range of 2.400GHz to 2.525GHz in 1MHz increments resulting in 125 channels to choose from. The controlling of the module is done using the SPI specification. The nRF24L01 supports amount of functions that are listed in the datasheet. What I like about these modules is they can be purchased with an external antenna socket allowing the attachment of an external antenna which can greatly increase their operating range.
ESP8266 WiFi Module
The third module we discuss is the popular ESP8266 which is a WiFi module that operates in the 2.4GHz band. This is great for the Internet of Things (IOT) applications to connect your projects to the internet. There are many ways to control this module. It can be connected to a microcontroller or programmed directly on it’s own. It is definitely the more complicated module of the three we’ve covered. To get this module up and running can be tricky especially for the first timer. It took me a few go’s just to get one of these modules to communicate with a terminate program to access the AT commands. To get the most benefit out of this module you’ll also need to learn about basic networking and webserver operations.
How to Select a Wireless Module for your Projects | Summary
So, I’ve given you a brief overview of the three main types of wireless modules commonly available. We have the 433MHz single channel module that uses a separate transmitter and receiver, the 2.4GHz transceiver module and the popular ESP8266 module. All modules are relatively cheap and can be purchased from online retailers for a few dollars.
The one you choose will depend on what you want to do with it. For example if you have a temperature sensor that needs to transmit data to a logger every few minutes, then a 433MHz module will probably do. If it’s multiple sensors and two way communications you require then the nRF24L01 would most likely be suitable. And if you have sensors that require two way communications and you want to be able to directly access the sensors over the internet then the ESP8266 would be a good choice.
I hope this tutorial has been useful to you.
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