There are many wireless technologies to create DIY connected objects. If you have complete control of your project. In this article we will take stock best suited to radio wave data transmission technologies for diy projects
WiFi is the choice most immediate. ESP8266 module especially since the project has become so popular in the Arduino community. The WiFi was not originally designed to develop connected objects. The initial idea was to get rid of ethernet cable to be able to make laptops more fun to use. WiFi is designed to cover a home. If you have a large garden and want to control your gate at 50 meters, you may have difficulties. You may have insufficient coverage and unstable. In this case, you can increase the range of your WiFi network with a repeater. The WiFi will also be ideal for making objects to interact with an online service (publish values on ThingSpeak for example).
Bluetooth is a short-range communication technology. The range of the Bluetooth (version 4.1) module is about 9-10 meters in open field. The version 5 promises 4x more data rate and 2x distance for the same energy consumption.
More reactive than WiFi, Bluetooth is well suited for performing radio controlled car projects, pilot an Arduino project with a smartphone … There are many Android or iOS app to control your projects from your smartphone.
The HC-05 and HC-06 modules are more common. You can find it for less than € 5. Programming remains quite simple.On can communicate by serial connection or using AT commands. Unlike ESP8266 modules that allow to execute the Arduino code, it will add a Bluetooth module for Arduino which increases the price of the project and its size.
XBee and Zigbee
The MaxStream XBee modules is a trademark of the company Digi International. They have been certified by the ZigBee Alliance in 2006 (IEEE 802.15.4). Zigbee is a Bluetooth cousin. While Bluetooth is primarily intended for use in public or a single user can connect to device (ideal for hands-free kit, headphones, remote control …), the Zigbee to create a network ‘objects. Zigbee is not designed to transfert a lot of data (250kbps max.). Zigbee is really reliable and secure. That is why the Zigbee is much used in the industrial world. The main characteristics of XBee/Zigbee are:
- Frequency: 2.4Ghz
- Transmission distance in free field
- XBee 1 and 2: 10 to 100m
- XBee Pro: up to 1000m
- Data rate: 250kbps
- Consumption: 3.3V @ 50mA
- Inputs / Outputs: x6 10-bit ADC input pins, x8 digital IO pins
- Security: 128 bit encryption
- Communication: via the serial port, AT commands and APIs
- flexible network: supports knots off, easy integration of a new node
- Maximum number of nodes: 65000
- Possible network topologies: mesh, point to point, point to multipoint
Zigbee is very well suited for home automation applications. Despite its many strengths, the XBee has not met with the same success as WiFi modules with ESP8266. It must be said that the price of modules rather high (about 23 € and 5.4€ for one Arduino Uno adapter) is a brake for fun DIY projects. For DIY projects the RaspBee board (about 35 € on Amazon) add ZigBee connectivity to a Raspberry Pi.
Other radio : 315MHz, 433Mhz, 868MHz, 2.4Ghz…
WiFi, Bluetooth, XBee are data transmission technologies by radio waves that carry the name of a trademark (a consortium or a company). There are generic radio modules that uses no proprietary communication protocol. There are two main ways to use these modules in your Arduino projects:
- Manage yourself communication between two devices. In this case, the library VirtualWire is all set for that purpose. Of course there are other libraries (MiRF, Radio …)
- Use the MySensors library in addition to support the transmission of data created and manages a network connected objects. This solution will be very well suited to develop your own sensors or actuators as part of a DIY home automation project.
Side hardware, there are so many that it is difficult to list them all, we will stay on the best known. If you want to use the library MySensors, the easiest (and cheapest) and opt for a nRF24L01+ (from Nordic Semiconductor). This module is also supported by the gateway RFLink.
Warning. Radio frequencies are subject to regulation (different in each country). You must ensure that you have the right to use the frequency band used by the module. So beware of cheap modules, of uncertain origin, not technical specifications.
Here are some very common modules found on Asian online shopping sites.
|XD-RF-5V : 315MHz|
It is one of the most common low-cost modules … but attention to performance (not recommended to make a gateway RFLink for example). There exist several frequencies : 315 MHz (XD-FST) or 433 MHz (XD-RF-5V). The transmission distance is about 200m (free field). Only 20m indoors.
|APC220 : 433MHz|
More professional module. With the APC220 module, you can choose the radio frequency from 418 to 455MHz. Supply voltage from 3.4V to 5.5V. Up to 1000m in open field. About 27 €.
|nRF24L01+ : 2.4GHz|
It is the most used radio module for MySensors. Now you can use it too for RFLink project. These modules operate at 2.4GHz (same WiFi). There are several versions:
With an external antenna, hopefully reach 1100m in open field at very low speed (check under real conditions).
LoRaWAN or Sigfox (868.1 MHz)
To close this list, here are the two latest communication technology by radio waves that grow very strongly now. They meet every two with the same problem. Propose a long-range wireless digital communication system (several kilometers). In this area, there are two major competitors : LoRaWAN and SigFox. SigFox can be regarded as a telecom operator as it provides a complete solution (protocol and antennas). SigFox is aimed mostly to industry and infrastructures (Smart City).
LoRaWAN : an open project
Lorawan (Long Range Wide-area network) was born following the acquisition of Cycleo by Semtech company in 2012. Today, LoRaWAN is supported by the LoRa alliance (Cisco, IBM, Actility, Sagemcom, Eolane, Microchip Technology, Bouygues Telecom, Orange, KPN, Swisscom, SingTel, Proximus …). In France, Orange and Bouygues Telecom are working to deploy their networks and offer new products and associated services. Although LoRaWAN is perfect for DIY projects, as completely open and royalty-free.
You must pay (every year) to use the Sigfox network. The SigFox network grows very quickly either own name as in France (92% of the population is now covered) or via partnerships (ARQUIVA in England, CELLNEX in Spain …). Sigfox develops local projects to equip large cities (Milan, Dublin, Munich, Seoul, Singapore …). SigFox is present in over 24 countries now.
Many products today rely on SigFox network, here’s a little preview. Generally, subscription fees SigFox network is included for the first month. Prices will depend on the manufacturer (about 20 € per year). You can start your project for approximately 85€.
Summary: What wireless technology to choose for a DIY project?
Rather than giving answers, the best to answer this question and help you choose wireless technology best suited to your project. Here are several criteria that you can consider:
- Transmission range: Short (remote control), medium (a hundred meters) or long (several hundred meters)
- Configuration: in a house, outdoor, mixed
- Wall: thickness, constitution (reinforced concrete does not really help), number
- flat or embossed
- Vegetation, fence
- electromagnetic disturbance: transformer, pumps …
- Running on battery or AC power
- Space available
- You manage communication
- The object will interact with an online service: IFTTT, ThingSpeak …
- Automation Server: MQTT, MySensors, RFLink, OpenZWave …
- Your level. If you begin, choose a technology used by a large community of users. You will find many examples and projects.
|2nd criteria||WiFi||Bluetooth||XBee||Other (433 MHz…)||LoRaWan or Sigfox|
|Configuration of the land||Esay|
|Protocol||Point to point|
To conclude this article, conventional radio ESP8266 WiFi modules and antennas (433, 868 or 2.4GHz) are the easiest and cheapest solutions to implement for self even develop online projects. If you develop a remote-controlled project, you can turn to the Bluetooth (or XBee). If this is a project for professional use (industry, logistics, medical, transport …), go directly to the Zigbee in association with LoRaWAN or SigFox.