Data Hacking

30 Part I — Hardware Hacks
6. Add a few dots of hot glue to the wires at the top to reduce the chances of shortcircuiting,
as shown in Figure 2-20. That’s it! All done!
TOP
Hot glue
FIGURE 2-20: Hot glue keeps the wires
in place.
Making Power Cords
Making power cords is similar to making data cables. The main differences between a data
cable and a power cord are that you need a cigarette plug and you connect to different pins on
the GPS connector.
There are some caveats to bear in mind. Not all GPS units can handle the full 12 volts from
an automotive system. Connecting some units directly to the system can cause serious and
permanent damage. The Garmin eTrex range and the eMap range take 2.5 volts, and 12 volts
will seriously damage them. These all use the rectangular connector and as such are easily
spotted. The Garmin Rino requires a 6-volt supply. Many others can take between 8 and
32 volts (usually making use of the round connectors) but there are notable exceptions —
in particular, the Garmin GPS-12, GPS-38, and GPS-40, which can take no more than
8 volts.
If you have any doubt about the power range that your GPS can handle, consult the user manual.
Specifications change regularly and it’s better to be safe than sorry.
If your GPS cannot take a 12-volt supply, you will need a cigarette adapter that can step the
voltage down. You can find plenty of cheap sources of these, in the form of old car phone
chargers or chargers for other devices. You can also find variable chargers that enable you to
control the output voltage. These are very handy, as they can be used for a variety of projects
(as long as you remember to set the voltage properly before each use).
Once you have a suitable cigarette lighter adapter, making the cable is easy. The power inputs
into a Garmin eTrex are pin 1 (+) and pin 4 (-), as shown in Figure 2-21.
Assembly is easy, as described in the following section.