What and why

I wanted to log Important telemetry data of my Surron Ultra Bee in my Grafana dashboard. That’s by decided to replace the default GPS tracker, with a custom build solution, You might wounder, why rebuild a whole tracker from scratch. I dit this mainly for two reasons, first and formost, if i want to resell the Bike, the next buyer properly doesn’t want a custom Tracker, and just wants the of the shelf thing.
The second reason (and properly the more important/ interesting one) is, that I wanted to build something that uses GPS and LTE. And that wat bather then a custom GPS tracker, because you have to handle things like data cashing (in case of connection loss), and much more.

Development and first bringup

The bord was designed with the Open source Software KiCad, with i really like because you can build custom GitLab CiCd pipelines fore exporting Gerber files and board renders, using Blender.
For coset reason i designed the board using a 2 layer PCB, witch in hindsight wasn’t ths smartest thing, but it worked for the most part just fine.
Because the board was designed to fit into the same footprint as the old GPS Tracker, it had to be realy small, with meant that THT parts were out of question, so each electronics part was SMD.
Soldering so manny, so tiny parts by hand really isn’t that fun, and also the LTE module, with is used, had pins on the bottom, with are impossible to solder by hand. So I tried something that I saw on YouTube, reflow soldering, using a freeing pan, and sand. This actually worked really well but also took like half an house of full heat of the camping heater, to heat up tha sand so much, that the solder paste would melt. (Tin foil is just so that the sand doesn’t come in direct contact with the parts)

First bringup was more or less uneventfully, after a redesign of the battery/power management, even the LTE module connected to cellular, and was able to download a test HTML page.

GPS and LTE antennas

I was thinking about including an onboard SMD or chip antenna. But i decided against it, for the simple reason of reducing complexity. The antenna of the LTE and GPS modules signal was just routed to an PCB connector, so I could connect a standard antenna. Both antennas were located on the side of the case with is facing upwards, to assure the best connectivity.

Comparison and final thoughts

When you compare the OEM tacker with my device (see tile image), you might notice that tha case is a little bit bigger, but it still fits in the pre determent spot of the bike. I might have to redesign the power supply/ battery circuit, because the Surron one in rated for about 50mA, but mine takes about 80-100mA. Otherwise, reading the bus and cellular/ GPS connectivity worked just fine.