Data Hacking

Chapter 2 — Building GPS Data Cables and Power Cords
FIGURE 2-21: Power pins of a Garmin eTrex connector
Power Cord Assembly
If you managed to assemble a data cable, then building a power cord is just as easy. The main
differences are how you hook up the pins. Pin 1 on the GPS connector is connected to the wire
from the center of the cigarette lighter adapter (the power supply), while pin 4 is connected to
the other wire (the ground). Remember that for most cars, the center pin in a cigarette socket is
the positive terminal, while the outer is negative, as shown in Figure 2-22. If in doubt, check
your vehicle’s manual.
As a safety precaution, make sure that the cigarette lighter adapter is fused to protect both the
GPS receiver from damage as well as the car from the risk of fire. If you are unsure, open up
the connector and see if one is fitted. If it isn’t, add an inline fuse (using a 5-amp fuse).
Testing
Make sure you use your multimeter to verify that the output voltages are correct and that there
are no short-circuits that could blow the GPS unit.
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