Paging A Mobile Phone With A Key Fob Part 1: An Introduction


It’s been awhile, two months I think, since my last blog post (I had some other priorities to tend to). But I have to say, getting back into this blogging routine wasn’t as easy as I would like, but it’s great to be back into it.

Looking back on previous blog posts, what stood out was that we tinkered with various technologies and tools that would help us to build an IoT solution, but there were not much in terms of connecting those ideas to build an end to end solution. So what I thought we can do this time around is to try a different format. We will take an “idea” and build it from start to finish, through a series of blog posts.

The Scenario

Back in the nineties (my teenage years), I remembered a friend of mine who had a pager which he usually have strapped to his belt. The device was pretty cool, doesn’t matter if we were down at Block Buster or at the local cinema, his beeper would go off and he would find a payphone and respond to the message.

A pager

In this blog series, we are going to build something similar but with an IoT approach.

Supposed we have a disabled family member or friend that is alone at home. Most of the time they can reach us via voice call or text, but supposed their phone were out of reach so they were not in the position to make calls or text. What if they had a wearable device on them, something that could send a notification to us with just a press of a button. We would then response as required.

The High Level Overview

We are going to be using a 433MHz key fob transmitter (and with a BLE version later on). It has 2 buttons (we are going to use one button to indicate assistance is required and the other button to indicate assistance is no longer required). A 433MHz receiver will be connected to a RPi (which is the gateway to a backend service). The backend will forwards it to a mobile network which in turn forwards it to a specified mobile number.

The high level sequence diagram above provides a rough idea of how the message is forwarded to Alice when Bob presses a button on the key fob (with the underlying protocols involved in parenthesis). However, we will be using services that will abstract away all those underlying protocols so don’t worry.

As you can see, there are a lot of bits and pieces to cover, so what I might do is break the whole thing into 3 parts:

  • Handle event via a Raspberry Pi
  • Forward event to the cloud
  • Notify recipient of event

What’s Next?

Well the 433MHz key fob and receiver arrived in the mail a couple days ago so I will give them a spin and post the next part in the series shortly.

Categories: Internet of thingsTags: , , , ,

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