Paul continues his dive into long-range wireless communications, this time turning his attention to practicalities such as which hardware and cables to buy.
Paul continues his dive into long-range wireless comms, this time turning his attention to practicalities such as which hardware and cables to buy
Last month’s introduction to LoRa and LoRaWAN was heavy on the theory that lies behind what makes LoRa communications work, and how it’s able to do so at such incredible distances using very low power transmission. This month, I’m going practical, with a look at some of the kit on offer and how things such as cables can be critically important.
But first, did you manage to grab a couple of those Heltec boards I mentioned in the previous column, and try some long-range tests? I hope that a few of you managed to – you should have found that you were easily able to pick up the signal from a mile or more away. That’s amazing when you consider that the board is tiny, low-powered and has such a small antenna. I’ll talk a bit about antennas later. And yes, fellow pedants, it’s “antennas” when talking about comms kit – antennae is the plural of the sticky-out bits on insects and molluscs. I often see people using the “ae” spelling for the techie stuff, trying to look clever but in fact looking the complete opposite.
This little distance experiment probably seems academic. Sure, it’s neat that you can send a message over a long distance using a low-powered device, but surely you could just as easily send an SMS from your phone to get a message between the two locations? Well yes, you could if you have mobile coverage, but there are loads of places on the planet that have no mobile reception – including some within a few miles of my house. Using these simple little LoRa boards, you could easily create a “chat” application that would work between climbers on the side of a mountain, for example, and even in the nottest of mobile not-spots.
Such point-to-point applications are all well and good, but LoRa and particularly LoRaWAN really comes into its own when you introduce a gateway. Think of it like a typical Wi-Fi setup: it’s possible to have two individual bits of kit talking to each other over Wi-Fi (there’s even a standard for it called Wi-Fi Direct), but it’s far more usual and useful to have all your wireless devices talking to a router located somewhere in your home or office. It allows the local devices to all see and talk to each other (else your laptop wouldn’t be able to send pages to your printer), but it also enables the local network to talk to the big wide world outside.
A LoRaWAN gateway is much the same. If a flower grower had a huge field with a few dozen LoRa-powered soil moisture gauges scattered throughout, they could all talk to a gateway located somewhere nearby, which could then send the data off elsewhere to be processed, perhaps even automatically switching on an irrigation system.
LoRaWAN gateways come in a few different flavours. Firstly, they are usually classed as indoor or outdoor devices. There’s no real difference to the radio side of things in either case, it’s just that outdoor gateways are more suited to an external environment, and as such they tend to be more expensive. I’ve seen blog posts and YouTube videos where people buy an internal gateway, take out the innards and then mount them in a separately purchased weatherproof box. That’s great if you’re bored and want a project, but I’m not sure how practical it is. Firstly, by the
“You could create a ‘chat’ app that would work in even in the nottest of not-spots”