Designing a Low cost OBD II 3G/2G GPS Tracker – Part 1

Details of the Requirement :

The requirements were very simple, 

  • The device should be able to connect to the OBD II port of any car and read data periodically and send to server via MQTT
  • It should have 3G internet connectivity and should be able to connect to OPTUS/VODAFONE network of Australia
  • Device should have a motion sensor for power savings
  • Bluetooth 4.x was needed for communication with Smartphones and initial configuration of the device 
  • Device should operate either from Vehicles OBD ports 12V input or from the internal battery with auto power path management
  • Device should have inbuilt antenna GPS module 

For the design we shortlisted the following parts,

SIM5300E for 2G/3G connectivity in European bands

SIM39EA for GPS location acquisition

STM32L4xx for processing and multi threaded low power operation and 4 UART ports

BM71 for Bluetooth communication

Scantools STN1110 QFN package for OBD interface

LIS3DH for motion sensing

U.FL Flex antenna for Network connectivity

Design was complete in 10 days and It took 15 days to get the bare PCB due to manufacturer delay and components were ordered in parallel.

In 25 days we had first version of the OBD tracker boards in our hand as shown below,

Here is a intro video on the boards initial looks,

In next video  i will show how the board works and a demo on my car which i bought to test the OBD trackers i am developing 😀 (Well, it was one of the reason)

P.S : This post was long due, and i am not getting time as earlier due to too many projects that i have taken up. Will try my best to post more often. 

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