My lighting unit needs to communicate with its minder by text message.
I got sort of an idea how to do this, but I'd be grateful if someone could fill in the gaps in my knowledge.
I think I need a GSM Modem to which I fit a SIM card. Can all GSM Modems send text messages? Could someone recommend one, either a module or a standalone unit.
The last time I interfaced to a modem, I was sending data down a telephone line. I used the UART in a microcontroller and sent commands that started with AT. From what I've read it seems the GSM Modem works the same way.
So there seems to be a command to contact a certain mobile phone number, and another to send a text message.
Is that really all there is to it? Or have I over-simplified it?

 

It is pretty much as simple as you think. The thing to watch out for now is the retiring of 2G and 3G systems obsoleting modules that can't work with 4G and 5G.

The SIM7600E is not cheap but it's fairly future proof. I don't know where to suggest buying one, but I think you should be able to find one from any decent supplier, or a breakout.

 

Pretty much as you suggest. The module that seems most liked is the SIM800L, around £8/$12 on Amazon. There a Arduino project on the Arduino.cc site and a Youtube video

Edited to add project link

 

Pretty much as you suggest. The module that seems most liked is the SIM800L, around £8/$12 on Amazon. There a Arduino project on the Arduino.cc site and a Youtube video

Yes, I have one here, but you need to read this. The SIM800L needs a 2G network and they are being retired in most places. If you have a 2G network locally, that's fine. If not, you need a newer module.

 

Let me make one more suggestion which you might like, or maybe not.

Take a look at particle.io. They have a unique model. For one thing, they include the cellular connectivity with the hardware. They have a free tier plan which might just be enough for you, and they have more. They support OTA updates and have all sorts of management thingies, with an online IDE.

It will take a bit to absorb, but if it is attractive, I can recommend them. I have some earlier generation hardware and it's been excellent. They also have WiFi only models that can be managed the same way. So you can keep an eye on the "fleet". It might not be your thing, but take a look, maybe it will strike a chord.

 

They retired the 2G networks around here quite a while ago, and the just shutdown the 3G which means my $50,000 BMW's online features are now useless, and there is no upgrade path. My older BMW has a 2G radio so it was dead long ago, but really, shouldn't something like that be modular?

It stinks because the car is still like new, and it's mechanically perfect but there is no way to get the online services which included useful things, like remote unlocking, remote cool down, at one point the cameras were able to be used remotely but for some reason they shut that off in North America, and real time traffic information in the satnav.

I am very reluctant to replace the car, though the technology in the newer models is great improved concerning driver assistance items like adaptive cruise control, collision avoidance, and lane maintenance. I would like to have those things quite a lot but... meh.

 

Yes, I have one here, but you need to read this. The SIM800L needs a 2G network and they are being retired in most places. If you have a 2G network locally, that's fine. If not, you need a newer module.

It must be 3 or 4y since I used the SIM800 module, I thought it was 3G as well. Not that it matters as 3G is being phased out too, but not til 2033 according to O2.

The 7600E is about £70 so my view,.assuming the above, would be to go with the 800 for now and upgrade later.

 

It must be 3 or 4y since I used the SIM800 module, I thought it was 3G as well. Not that it matters as 3G is being phased out too, but not til 2033 according to O2.

The 7600E is about £70 so my view,.assuming the above, would be to go with the 800 for now and upgrade later.

So you have 2G? That's great. You can also get more common pattern Particle hardware for 2G and 3G in Europe... err... old limey..

 

There's even 4G (and 5G in places, but not within 30 miles of here).
What I'm not sure about is the phasing out of 2G.

 

@Ian0 this looks interesting if the data totals are sufficient for your application: https://portal.1nce.com/portal/shop/

They have a UK SIM that is €10 for 10 years duration and 500MB of data and 250 SMS messages.

 

Thanks, everyone. I'm going to build one and see if it works, once I've found out what G-numbers are operational here.
[Update] https://www.bbc.co.uk/news/technology-59583783
I think I need to be aiming for 4G.

 

It probably depends on your timescale:
UK to phase out 2G and 3G by 2033

but some probably sooner
Vodafone to switch off UK 3G network by end of 2023

 

It probably depends on your timescale:
UK to phase out 2G and 3G by 2033

but some probably sooner
Vodafone to switch off UK 3G network by end of 2023

Yes, the 2033 date is a government initiative, but the carriers seem to be more anxious to get on with it.

It benefits them a good deal. In general it is a benefit to the public as well, unless you are happy with your old phone and would prefer not to upgrade, or want to use a SIM800L.