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Transcript power - NMEA
Dealer Certification
Section 2: Building the Network
Physical Planning & Documentation
Power Sources & Distribution
Voltage Drop Calculations
Copyright © 2011 NMEA
Physical Planning & Documentation:
Power Application Example
Physical Planning & Documentation:
Planning the Physical Layout
Determine Device Locations on the vessel
Determine Backbone Path through the vessel
– Passes within 6 m of Each Device
– Less than 100 m End to End (250 m w/heavy cable)
– Backbone Must Not Branch
Determine Power Source and Application Point(s)
Physical Planning & Documentation:
Planning the Physical Layout
Select Cable Type
– Either Light (Most Common) , Mid or Heavy
– Ensure Total Power Does Not Exceed Cable Rating
Determine Power Source and Application
Point(s)(Power Tees)
More than one power application point IS allowed and
MAY be needed as network size increases.
Physical Planning & Documentation:
Start With a Backbone Diagram
1. The length of each network segment and drop
cable; location of tees and terminations
2. The identity and network LEN of each
equipment on the network
3. The planned location(s) where power will be
supplied to the network
4. The single location where the shield/drain wire
will be connected to vessel’s non-current carrying
RF ground.
Physical Planning & Documentation:
Start With a Backbone Diagram
A completed network diagram contains all
information necessary to complete the voltage
drop calculations
Defines all cables, connectors, & devices needed
for the complete installation
Physical Planning & Documentation:
Load Equivalency Numbers (LEN)
Representation of the amount of current a device
uses from the bus
All devices have a LEN equivalency number (LEN)
The device manufacturer publishes this number
Physical Planning & Documentation:
Load Equivalency Numbers (LEN)
1 LEN = 50mA , 20 LEN = 1 Amp
Maximum LEN a single device can power from bus = 20
LEN is used to determine the voltage drop
The higher the LEN, the higher the voltage drop
Physical Planning & Documentation:
Less Than 5 Devices
NMEA 2000® Backbone Provides Power to Devices
Network Devices Require 9 to 16 VDC
Most NMEA 2000 devices get power from the bus
POWER INSERTIOIN POINT
Physical Planning & Documentation:
5 Or More Devices
2 meters
0.3 meters
0.3 meters
POWER
2 meters
6 meters
0.3 meters
0.3 meters
5 meters
2 meters
2 meters
Power Distribution:
Backbone Electrical Connections
Power Source Options
–
–
–
–
Ships Battery Connection (12.5 VDC)
Isolated DC to DC Power Supply (13.8 VDC)
Isolated AC to DC Supply (13.8 VDC)
Multiple Power Supplies (13.8 VDC must be consistent)
Backbone Shield Connection
– Only Connected at a Single Point (Single Power Tee)
– Connected to the non-current carrying RF Ground
Power Distribution:
Power Source Considerations
Voltage Drop on Backbone Limited by
– Voltage Available (Including Distribution Losses)
– Voltage Required
– Operational Common Mode Voltage Range : ± 2.5 VDC
Power Source Dependability
– Minimum Battery Voltage = 11 VDC
– Maximum Power Supply LEN Variation = 5%
Power Distribution:
Multiple Power Sources
Split Power
– Compute Voltage Drop as for a Middle-powered
Backbone
Isolated Power Supplies
– Each Power Supply Drives Backbone Segment;
Compute Voltage Drop for Each Supply as End or
Mid-powered
Power Distribution:
End-Powered Backbone Example
3 meters
Power is traveling right only
POWER
2 meters
6 meters
2 meters
5 meters
0.3 meters
Power Distribution:
End Power- Single Battery Example
NET-L
NET-H
NET-S
NET-C
Shield / Drain
Power Distribution:
Middle-Powered Backbone Example
2 meters
0.3 meters
0.3 meters
Power is traveling left & right
POWER
2 meters
6 meters
0.3 meters
0.3 meters
5 meters
2 meters
2 meters
Power Distribution:
Isolated DC Power Supply Example
NET-L
NET-H
NET-S
NET-C
Shield / Drain
Power Distribution:
AC Power Supply Example
NET-L
NET-H
NET-S
NET-C
Shield / Drain
Power Distribution:
Network Node Example (In Device)
CAN CONTROLLER
TRANCEIVER
I/O
Isolation between Transceiver and CAN Controller
Transceiver is Powered from Network Power
Power Distribution:
Dedicated Power Cable Routing
– NMEA 2000 Transceiver circuit is powered by the backbone
– Main power for LCD screen etc. is not powered by the
backbone
Device is more than 20 LEN
Dedicated power (separate from backbone)
Devices powered from backbone
Data & power for NMEA 2000
Transceiver ONLY
Drop Cable without power wires
(provided by manufacturer)
Power Distribution:
Larger Networks
Multiple power T’s are needed when voltage
drop calculations exceed limits.
Power
Additional Power Tee
Only connected to the Right
Power Distribution:
Multiple Power Supplies
– Shield/drain wires (grey) are all tied together and only
bonded to RF grounding at one power insertion point
Power Distribution:
Larger Networks
Heavy cable backbone
Heavy Tees with Light / Mid drop connection
Allows for drop cable to connect into all devices
Light cable drop connection
Voltage Drop Calculations:
Battery & Power Supply
Battery Powered Distribution Loss Budget
Minimum Battery Voltage
11.00 VDC
3% Loss at Insertion
- 0.33 VDC
Backbone Distribution Loss
- 1.17 VDC
Minimum Voltage at Device
9.50 VDC
Power Supply Powered Distribution Loss Budget
Nominal Power Supply Voltage
13.80 VDC
5% Output Variation
- 0.75 VDC
Backbone Distribution Loss
- 3.55 VDC
Minimum Voltage at Device
9.50 VDC
Voltage Drop Calculations:
Why Do We Need Them?
Needed to ensure that all devices on the
network are getting adequate power.
Devices furthest from the power insertion point
will get less voltage than the closest device.
More than one power insertion point (Power
Tee(s)) may be needed to feed all devices.
Voltage drop calculations help us determine this.
Voltage Drop Calculations:
Calculating the Voltage Drop
VOLTAGE DROP CALCULATION is Ohms Law;
E= I x R
E = Voltage Drop (VD)
I = Total Network LEN (NL)
R = Backbone Length (BL) in Meters (one way)
VD=.1 x NL x BL x Cable Resistance
– Cable Resistance Is in Ohms (Ω) per Meter
– Light Cable = .057 Ω
– Mid Cable = .015 Ω
– Heavy Cable = .012 Ω
Voltage Drop Calculations:
Example
Network LEN
Network Backbone Length
Cable Resistance-Light
Voltage Drop Estimate
13
14.3
.057 per meter
1.06 volts
E= I x R ( Ohms Law)
E = voltage drop (VD)
I = total network LEN (NL)
R = backbone length in meters (one way) (BL)
VD=.1 x NL x BL x .057
1.06= .1 x 13 x 14.3 x .057
Voltage Drop Calculations:
Calculator Keystrokes- EXAMPLE
NL (LEN) = 7
BL (Length) = 5.0
Cable Type= Light (.057 Ω / m)
Calculator Keystrokes are…
.1 x 7 x 5 x .057 = 0.1995
Round up at second decimal place → .20
Voltage Drop Calculations:
Calculator Keystrokes- EXAMPLE
NL (LEN)=3
BL (Length) = 4.2
Cable Type= Light (.057 Ω / m)
Calculator Keystrokes are…
.1 x 3 x 4.2 x .057 = 0.07182
Round up at second decimal place → 0.07
Voltage Drop Calculations:
Calculator Keystrokes- EXAMPLE
NL (LEN)=12
BL (Length) = 9.8
Cable Type= Light (.057 Ω / m)
Calculator Keystrokes are…
.1 x 12 x 9.8 x .057 = 0.67032
Round up at second decimal place → 0.67
Voltage Drop Calculations:
Calculator Keystrokes- EXAMPLE
NL (LEN) =15
BL (Length) = 20.3
Cable Type= Heavy (.012 Ω /m)
Calculator Keystrokes are…
.1 x 15 x 20.3 x .012 = 0.3654
Round up at second decimal place → 0.37
Voltage Drop Calculations:
Calculator Keystrokes- EXAMPLE
NL (LEN)=19
BL (Length) = 28
Cable Type= Mid (.015 Ω / m)
Calculator Keystrokes are…
.1 x 19 x 28 x .015 = 0.798
Round up at second decimal place → 0.79
Voltage Drop Calculations:
When Do We Calculate Segments?
When VD exceeds 1.17 VDC using a ship
battery powered network
When VD exceeds 3.55 VDC using a regulated
13.8 VDC power supply
Battery Powered Distribution Loss Budget
Power Supply Powered Distribution Loss Budget
Minimum Battery Voltage
11.00 VDC
Nominal Power Supply Voltage
13.80 VDC
3% Loss at Insertion
- 0.33 VDC
5% Output Variation
- 0.75 VDC
Backbone Distribution Loss
- 1.17 VDC
Backbone Distribution Loss
- 3.55 VDC
Minimum Voltage at Device
9.50 VDC
Minimum Voltage at Device
9.50 VDC
Voltage Drop Calculations:
Calculating the Segments
Enter devices starting at the device closest to
the power insertion point.
Enter segment lengths starting with the segment
between the power insertion point and the first
device.
Always use the last drop length as part of the
total backbone length calculation
Compute currents.
Compute voltage drop in each segment for each
device.
Add the voltage drops in the column.
Voltage Drop Calculations:
Segments on the Network
Calculate segments
left of power
Calculate segments
right of power
Voltage Drop Calculations:
Left Side of Power Tee
Voltage Drop Calculations:
Left Side of Power Tee
Voltage Drop Calculations:
Right Side of Power Tee
Voltage Drop Calculations:
Right Side of Power Tee
NEXT: Section 3
Connecting to Other Data Sources and Networks
&
Advanced Setup, Certification, Troubleshooting
Copyright © 2011 NMEA