There are existing solutions out there to prevent such tragic incidents. Starting from printed stickers and up to complex IoT systems connected to the cellular network. I am not inventing something new. So what made me design and implement a system of my own? The reason is that I was not happy with the existing systems for various reasons. I will describe my key requirements for such a system in more detail.
But first a short disclaimer: any device you might use for this purpose is a backup. It is not meant to be a replacement for your responsibilities. It is merely a last resort when all else has failed. Having said that, I think that installing a device like this is a responsible thing to do, because even though the chances are slim, cases like this happen yearly.
Alert, not a reminder
It is all about the timing and the level of certainty of the alarm. Many systems will notify you that a child seat is occupied when you open the door, turn off the car or stand up from the driver’s seat. However, that is merely a reminder. You might have just been planning to open the back door and take the child with you, but the system doesn’t differentiate. Worse, you might hear the reminder and plan to take the child, but then something might happen and you might get distracted. When using a reminder system, you would get these reminders all the time, as often as several times a day. You might get used to these reminders, they might lose efficiency and affect your routine.
A key requirement for Fochica was to be an alert. Meaning to know when the adult left without taking the child out of the seat and to sound an alarm at that time. This should be a rare event, probably due to a false positive rather than an actual incident (which are very rare). Such an alert would draw much more attention due to the context and certainty it conveys.
To know when the adult and the car are apart, some type of communication must happen between the two parties. Additionally, each of the two parties must have a device to facilitate the communication, a receiver and a transmitter. Naturally this makes an “alarm” system more complex than a “reminder” system but since an alarm can also fall back to being a reminder, I couldn’t see any other cons for this design.
Some similar implementations are available where an adult must carry a special dongle/keyfob that communicates with the device in the car. A key requirement for Fochica was to use something that a user would already have, a smartphone, as the “terminal” for the adult. This way I didn’t have to design a compact device for the adult, overcome challenges of reliably powering it, increase the cost by introducing more parts, etc. Using the phone also carries several advantages, such as a rich UI, IoT connectivity, etc.
The decision to use smartphones for one side of the communication basically limits the communication protocol options to Wifi, Bluetooth and BLE. I have decided to use BLE due to the low energy property and the growing support in smartphones. BLE modules are also available for as low as $3 on eBay so they are “approachable” for hobbyists.
The downside of this approach is the dependency on the smartphone. The assumption is that we now carry our smartphone everywhere with us. The chance of having the phone with us is high and the chance of forgetting both the phone and the child in the car is lower than forgetting just one. Still, if the phone is not available, the device in the car will operate in “reminder” mode as a fallback measure.
Some implementations exist where the user must turn the system on when placing a child in the seat (arm it) or turn it off when taking the child out, or put a beacon on the child, or start an app, or do something on a routine basis that he wouldn’t have to do if he was not using such a system. This creates nuisance to the user and faced...
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