Transient Voltage Suppressor

This simple circuit can be laid out on some protoboard to clamp any high voltage spikes that may damage the Imp's DC/DC converter. I used a TVS diode with a breakdown voltage of 15.2V and a PTC with 0.5A holding current. The PTC will prevent the TVS diode from getting too hot should there be an extended high voltage condition. The battery is connected through the STN1110 breakout board's Vbat pin and V+ is connected to the Imp's Vin.

Wiring

Depending on your enclosure there are many ways to lay out the physical boards. I will provide the connections for each and leave it as an exercise to the reader to sandwich them together. Make sure to keep the GPS module above any ground planes so it can see the sky unimpeded.

• RX-I → Imp Pin Q
• TX-O → Imp Pin R
• GND → GND

• TX → Imp Pin G
• RX → Imp Pin F
• Vin → Imp 3V3
• GND → GND

• SCL → Imp Pin A
• SDA → Imp Pin B
• 3V3 → Imp 3V3
• GND → GND

Using some 0.1" headers for the Imp and GPS I managed to get everything onto the protoboard I built the transient voltage suppressor on.

KML Track Server

Checkout the git repo for the track server which is a simple Python app that will pull data from Firebase and feed it to Google Earth as KML. Rename example_config.py to config.py and insert your Firebase info. Make sure you also update the Firebase name and key in the Imp's agent code. Once the Imp is logging data to Firebase, we can run the track sever with

$ python server.py

Initialize (http://localhost:5000/initialize):

Updates (http://localhost:5000, make sure to set the refresh settings as shown):

If everything goes well you should now be able to see the GPS location of the car with accompanying stats.

Right clicking on OBD Tracker and selecting "Show Elevation Profile" will enable the graph pane. Up to two engine stats can be graphed at a time.