Be sure to consider the design decisions described in the previous sections. When you are ready to begin installing the LMU, follow these steps:
5.3.1 Place the LMU unit in the vehicle.
Typically, the LMU should be placed under the passenger seat or dashboard of the vehicle. LMUs with internal antennas should be placed to
maximize their GPS performance. A typical location include under the dash close
to the front wind-shield.
Attach the LMU to the solid body of the vehicle, not to plastic panels. The LMU can be placed out of sight by removing interior trim and molding
to expose available space, then replacing the trim once the LMU is in place.
5.3.2 Connect power, ignition, and ground.
The power input (red wire) must be connected to a constant (un-switched) +12 VDC or +24 VDC supply; preferably, connected directly to the
vehicle battery terminal or as close to it as possible. This connection point
should be fuse protected to not more than 5 Amps.
The ignition input (white wire) must be connected to the vehicle ignition or another appropriate key operated line, such as ACCESSORY,
ensuring that power to the ignition wire is available only when the vehicle ignition is
on.
The ground line (black wire) must be connected to chassis ground.
Failure to connect these lines in the manner described may result in discharge of the vehicle battery.
For best results, it is strongly recommended that the LMU connection be on its own circuit. Connect the power input directly to the vehicle
battery if possible and protect the circuit with an inline fuse. If you must connect
through the fuse box, use standard commercial wiring practices to create a permanent installation rather than using press-in fuse clips or other
temporary measures.
DO NOT connect the power cable to the LMU at this time.
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5.3.3 Place the GPS antenna.
The GPS antenna must have a clear view of the sky. Mount the GPS antenna on the vehicle’s highest point (for example, the roof of a car). Make
sure that there are no obstructions close to the antenna that might block the
view 360° to the horizon. Air horns lights, vents, etc.. should not block the antenna beyond 5° above the horizon.
Kinks or knots in the antenna cable can prevent the GPS receiver from operating properly. When laying out the antenna cable, take care that the
cable is not subjected to crushing or strain.
The ideal location is typically near the center of the vehicle’s roof. However, it is also desirable to locate the cellular antenna as far from the GPS
antenna as possible.
GPS Antenna Location
5.3.4 Mount the Comm. Antenna.
When using separate Comm and GPS antennas, it is best to locate the Comm. Antenna at least 3 feet from the GPS antenna. Ensure that the cable
is not crushed during installation or normal vehicle operation.
Again, the Comm. Antenna must be located at least 20cm away from vehicle passengers, other personnel, or bystanders in order to comply with
FCC radio frequency exposure limits.
Window Mount Antenna Location
5.3.5 Typical Connection Sequence
Attach the cable from the GPS antenna.
Connect the cable from the Comm.. antenna
Connect any peripherals to the LMU
Plug in the power harness.
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The physical installation of the LMU hardware is now complete.
Completed Install – separate antennas
Completed Install - Internal antennas
5.4 Installation Verification
In many cases it is desirable to verify that an installed LMU-5541
™
is working properly. That is, installers should verify that the GPS and
communications functions of the LMU-5541
™
are working properly before
departing the installation site. In more robust cases, some key configuration settings such as the Inbound Address and URL should also be
verified.
Note that these processes are all based on issuing AT Commands to the LMU-5541
™
. It is expected that installers will have access to a serial
port expansion cable and a laptop or PDA capable of a terminal connection.
Alternatively, an SMS message can be sent to an LMU-5541
™
to obtain its current status.
5.4.1 Comm Verification
Installers should first verify that the LMU-5541
™
has been acquired and has registered to the wireless network. This may be verified in one of
two ways. First, installers may look at the Comm LED (i.e., the one closest to
the SMC antenna connector). If this LED is solid, then the LMU has registered to the network and established a data session.
If the LED is not visible, then Comm may be verified using an AT Command:
ATIC
Depending on the wireless network being used something similar to what is shown below will be displayed. It is important to verify that 'Yes'
values are displayed at the top for Data and Network registration and the correct
APN is displayed.
Radio Access : GSM
Network Reg. : Yes, Home
Data Reg. : Yes, Home
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Connection : Yes
RSSI : -97 dBm
