28 Feb 2021

Homemade Car Tracker

Spring is nearly here so naturally I found a homemade car tracker after sorting out some long-forgotten boxes.

Sounds cool?

It is not as cool as it sounds though. It’s a project from 2007 and is basically a Nokia 5110 with the outer case taken off and wired up to 3 AA batteries instead of the original battery.

High Quality Tracking Device

High quality tracking device!

I loosely remember my Dad and I finding the instructions for this build online and deciding it was a sufficiently good idea to carry out. I did find a printed copy of those instructions as well. I thought about scanning the pages to store with this post but to be honest it’s not that interesting. It’s three full pages of text which can be summarised as: Reset the phone, remove case (including speaker and ringer), remove LCD and power switch before finally bridging the switch contact points to be always on.

You might be thinking, why the Nokia 5110? I reckon it was chosen as it has somewhat of a reputation for being indestructible (maybe all old Nokias do?). Even when stripped of most components it still had some meaningful LEDs on the circuit board, so even without a ringer or LCD screen you could tell if it was on and working.

You might also be thinking, why bother doing the conversion? Just leave the phone hidden somewhere in the car? I think the idea is partly that it would be easier to have a rotation of batteries with the 3x AA setup, partly it’s less likely to be accidentally rung (and discovered) or more likely beep due to a periodic ‘this phone is being tracked’ SMS message.

How does the tracking work?

To actually use this as a tracker we used a service called ‘Follow Us’. The site appears to be long gone but it’s still around on Wayback Machine. Bonus reason to visit: It’s a web design blast-from-the-past. I assume it was network-based. With my basic understanding that is the phone connects out to a bunch of base stations/phone masts and based on signal strength you can triangulate a position.

Follow Us setup guide

Setup Instructions. Looks legit.

Follow Us was a ‘track a mobile number’ service. The site didn’t let just anybody sign up to track a mobile number though. You had to register, then get sent a pin in the post to verify your address. The mobile number you wanted to track then had to send this PIN via SMS to a specific number. The setup letter even has a reference to Home Office guidelines!

From memory after activation we tried tracking the family car once to prove it was working and then never again.

A quick search shows there are still plenty of services like this available now, some of which don’t appear to need any identity verification, which feels intriguing/suspicious. I’m tempted to try one out to but will leave that for another day. Doesn’t feel like the sort of website you want to input any meaningful mobile number…

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