Communicate 2 arduinos over 50km+. Possibly using bluetooth, phone data, email?

The simplified version of my current project is I want 2 Arduinos to communicate over 50km+. I will have a phone within a few feet of each arduino which means possibly Bluetooth or phone data is an option. I was thinking perhaps something even wilder like email or sms could be explored. Or perhaps I need to create a phone app that the arduinos communicate through, not sure.

The longer version of what I am trying to accomplish is the following.

If User A clicks button A attached to Arduino A then an LED that is attached to Arduino B turns on. This works both ways too. So if User B clicks button B that is attached to Arduino B then an LED that is attached to Arduino A turns on.

Oh, like yet another version of the love lights?

As long as both sides have access to mobile network it’s easy. You could connect both sides to a SIM module, give them a SIM card, and send SMS to the other side. Just make sure you have a big enough SMS bundle.

Or use the mobile data connection, connect both sides to an MQTT server, and have them send messages back and forth that way.

Not sure what Love Lights are. The company I work for wants me to try to make something that allows workers to communicate with their offices when they are off location - while also trying to get people off their phones. Simplest form of communication in my eyes is a light. The MQTT server route might sound best as the budget for the project per pair isn't much.

A light that goes on so your sweetheart knows you think about him/her.

Can also be used as a "please call me" signal of course. I don't see any practical use of such an arrangement but it's kinda sweet.

wvmarle: A light that goes on so your sweetheart knows you think about him/her. I don't see any practical use of such an arrangement

Yeah a more practical project would be a light that comes on when you're thinking of someone ELSE ;)

No, that'd give away you're cheating.

Update. Pretty much back where I started. I explored using a NodeMCU using my phones hotspot as wifi to send messages over mqtt but realized too late that if a device is connected to my phone via hotspot, I cannot connect my phone to wifi. I can't have that unfortunately. This device is meant to be a wearable so now I'm stumped.

The Sim card route is also not an option. Does anyone have any other ideas? Perhaps something involving bluetooth? or perhaps I somehow connect the device to an app on my phone? Would it be feasible have Arduino A communicate via bluetooth to an app on phone A which then communicates to the same app on phone B which then communicates via bluetooth to Arduino B?

HC-05 or HC-06 adapter (or something a bit more modern) would do, unless you have an iPhone. Then you need a special kind of BLE or so (I don't have an iPhone, largely as they're not compatible with anything but iPhone). That'd get you to your phone while the phone can be connected to the WiFi.

There must be ways of having apps talk to one another.

Hi guanciale,

I had the problem of not hearing my phone notification due to room noise. I was missing calls or messages from a certain important person.

I developed this:

Arduino Nano connected to a HC-05 bluetooth and an app I made on my Android phone;

when an SMS arrives from a certain phone no. the app sends a code to the HC-05;

the Nano detects the code and sounds a loud buzzer;

I press a button connected to the Nano & it sends a code to the phone;

phone app detects the code and sends an empty SMS to the phone no.;

This tells the caller I have got her SMS.

None of this was hard. There are lots of tutorials to help with both bluetooth and Android apps.

Does that begin to meet your needs?

John.

guanciale: The simplified version of my current project is I want 2 Arduinos to communicate over 50km+. I will have a phone within a few feet of each arduino which means possibly Bluetooth or phone data is an option.

For distances as far as that the phone network is the only realistic option. Which immediately raises the question, why bother with an Arduino. Why not just write an app for the phones that communicates over the internet (or using SMS messages).

Bluetooth is a short range wireless system for distances of the order of 10 metres. It could be used to link an Arduino to a phone but you would still need an app on the phone to do the long range communication so why bother with the Arduino.

You could probably easily build a phone App with either MIT AppInventor or QPython.

...R

Very strange requirement indeed. You want to contact a person but not via phone. Pager?

The OP has said that the company wants the workers to stay off their phones. Perhaps they might be driving operating machinery or up trees or power poles.

In my case I just don't hear the phone.

Lone worker safety is a serious issue. A rapid way to send a call for help is a good idea. There are commercially available device for workers such as nurses and social workers who may be in a dangerous situation with a patient or client and need to send a silent call for help.

A farm worker died after being staked thru the foot by the tine of a plough. He couldn't get back to the tractor cab and perished from heat exhaustion. A device on his belt that could send an SOS could have saved him.

Some injuries can incapacitate a worker so they may not be able to use a phone.

The OP's idea is worth developing. It would be simple to include a GPS module so that the device could send to base the location.