Instrumentation often needs connection back to ‘host’ equipment; be it a display, controller or logger.
While copper wire remains the common method for industry, there is often times when running cables might be inconvenient or hazardous. Connecting by radio offers a great solution, but like so many technical things, there are almost too many choices. This article seeks to summarise some of the options.
There are at least 5 wireless connection schemes, so knowing what to choose may appear a bit daunting at first.
Below is a summary of each type. These are typical uses only and vary in a case-by-case way.
Each system has its own advantages and disadvantages or design uses and these are discussed below.
Note 1: 2.4 GHz is another name for 2,400 MHz so about 20 times higher in frequency than your local FM radio station.
Note 2: All these methods of communication are by Radio Frequency (R.F.) but we tend not to think of these as radio; calling them by their technical names.
Most of us use Wi-Fi almost every day in our home or office networks. This is the standard method of connecting laptops, iPods, iPhones, Android phones, Tablets etc. to our networks.
Wi-Fi most often operates on the 2.4 GHz band. This band has become so widely used, that in urban environments, overlapping users may present problems. Cordless phones, baby monitor and even microwave ovens operate around these frequencies.
Another frequency band was added to alleviate this problem. A 5-GHz band is available and had very little uptake in most places, so offers a very good alternative for this reason alone!
The screenshot below shows a very typical example of Wi-Fi crowding, with at least 10 Wi-Fi stations in range! If your device supports 5-GHz, it’s good to use it.
An in depth discussion of the other Wi-Fi types is beyond the scope of this article, but in an extremely shortened summary…
Below is a picture of a typical wireless industrial pressure gauge using the Zigbee protocol.
Bluetooth is a ‘wire replacement’ technology predominantly. Cordless headphones, cordless mice and keyboards and some instrumentation use this technology.
Bluetooth has a fast data transmission rate (up to 25 Megabits per second). Networks are small (maximum 8 nodes) and range is typically short.
Nearly all mobile phones and laptop computers have Bluetooth built in and this ubiquity makes it attractive as no computer-side hardware is needed to be added.
Various iterations of Bluetooth means that it’s important to ensure ones hardware has a version compatible with the sender. For example, Bluetooth 2 dongles are still sold and here at the Homersham office we had trouble trying to use a version 2 dongle with a logger using version 3.0.
Not relevant to data transfer, but if one wants to use Bluetooth for audio, make sure your system has the A2DP profile (Advanced Audio Distribution Profile).
PC’s without Bluetooth can have this functionality added via a USB dongle. Most sender devices have a Bluetooth PCB embedded, but sometimes can be added as an add-on. E.g. The image below shows an add-on Bluetooth transmitter for a logging thermometer, an embedded Bluetooth PCB and an add-on dongle
Near Field Communication is the newest technology for wireless data transfer. It grew out of the RFID concept.
NFC is deliberately very short range (perhaps 100 mm) so lends itself well to security conscious applications such as keyless entry and EFTPOS.
One completely unique feature of NFC is that some uses may require no internal power e.g. your Paywave or Paypass card doesn’t have a battery.
The NFC terminal shares its power by generating an electromagnetic field which coils in the card pick up, and use to power the ultra-low-power circuits in the card. Of course when used in phones, the phone powers the NFC transfer.
NFC uses very low frequencies (compared to Wi-Fi etc.) at around 13 MHz; right in the middle of the Short Wave radio band.
Where national or even international coverage is required, the cell phone network can be used to send SMS (text) messages or e-mails while monitoring industrial processes. And of course it can often log in VPN (Virtual Private Network), RDP (Remote Desktop Protocol) or other software, from a PC as if you’re at your work terminal.
The caveat is of course cost. One wouldn’t normally use the cellular network to monitor an industrial process for extended periods in real time.
Be cautious about importing RF products on-line, into New Zealand. RF frequencies around the world vary. Using products from other countries may be illegal, costly or in a worst-case-scenario, cause harmful interference to other services.
Our article barely ‘scrapes the surface’ of this complex topic. The internet has many sites with in depth discussion if you require it.