Nav-Electronics Packge



 
One of the first things that we did on the boat is to modernize the navigation electronics on board. This was necessary as we intend on taking a few trips, and navigation equipment really helps in that regard.
 
Before going into an in-depth explaination of the navigation electronics, explaination of a few electronics terms are in order:
 


A Tour of the system

The first consideration in creating a nav-electronics package is how to power it. Considering radar and a VHF transmitter, a surprising amount of power is going to be needed at the helm. As well, in a boat such as mine, with a flybridge, cabling distances also play a role in powering the system. Therefore, a sufficient power source must be engineered into the system. In addition, a few components consist of small modules, so a method of mounting those devices is required. This requirement was solved as shown below:

This mounting board is located forward of the helm, and is out of the weather. The board includes an 8AWG wiring bus from the main power source to the helm, fused distribution block, ground block, interconnection strips, AIS receiver and Sonar module.

Next, a method of controlling all of the various components was required. This was accomplished by the addition of a switch module. From left-to-right, the switched circuits are, 1-elecronic compass, 2-sonar module, 3-GPS Receiver (which also powers the SeaTalk network), 4-power for the NMEA0183 network, 5-NMEA2000 power, and 6-AIS Receiver.

Since there are still some NMEA0183 devices that need to be networked into the system, a multiplexer is used. In a sense, a multiplexer behaves like a network switch, and combines up to 4 signals onto a single input. The Compass, AIS Reciever, and VHF Radio are connected into the system by this method.

At the helm, one upgrade is a digital fast-heading/fluxgate compass. This is a fancy name for a solid-state compass. It works on the same magnetic principle as a traditional compass, but with the addition of a digital output signal. This signal provides accurate heading information 10 times per second into a RayMarine C-80 Multi-Function display.

On the right side of the dash, a small NMEA2000 data display is located. This display can show Trim Tab position as shown here, as well as many other parameters, such as water depth, water temperature, speed of boat, GPS coordinates, and port and starboard fuel tank levels. Each data is displayed by flipping through screens on the display. One notable feature is a pop-up capability. Normally, an important reading is displayed, such as water depth. However, when the trim tabs are changed, the display automatically changes to the trim tab display. A few seconds after the trim tabs are moved, the display then automatically changes back to depth.

The main display unit in the nav package is a RayMarine C-80 shown here. It has the capability of displaying multiple screens simultaneously, or a single screen at a time. Shown here, in the upper-left quadrant is a chartplotter, in the upper-right is radar, lower-left is a data display, and in the lower-right, a sonar.

An advanced feature, AIS (Automatic Identification System) allows ship-transmitted data to be displayed on the screen. Shown here are three AIS transmitting ships within range. This information is broadcast by the ship on a periodic basis, and picked up by the AIS receiver. Each ship "target" has its current bearing and speed displayed, and if there is a chance of close approach, the time and distance of closest approach are displayed.

Any AIS target can also be highlighted for additional information, such as the ship's name, speed, length, cargo, destination, and a host of other information. Currently all commercial ships are required to transmit AIS in all federally controlled waters, including those ships on international voyages, those operating in coastal areas of the US, as well as the Great Lakes.

The Radar's MARPA (Mini Automatic Radar Plotting Aid) function is a feature that tracks any dangerous targets in the vicinity of your boat, or where your boat will be. It will plot the closest distance of approach (how close the two boats will come together) for purposes of collision avoidance.

An adjunct display allows select data to be displayed. This is useful for speed, depth, fuel flow, and other networked data, and a larger reading display is useful in keeping critical data at hand. Like the other displays, there are several pages of data that can be scrolled as conditions warrant.

Even the VHF radio gets into the act. This radio is connected to the Nav system for DSC (Digital Selective Calling) purposes. Should an emergency occur, by depressing the emergency button, the boat's identity (MMSI Number) and GPS coordinates are transmitted. Conversely, any received DSC signals, whether they be from a buddy boater or received emergency signal will be plotted on the chartplotter.


Detailed description of helm electronics

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