VDO Bus Limitations
The Nav Box provides power to all the 110mm gauges and 4.3’’ TFTs
connected to the system. Due to the power consumption and the resistance of
the cables there are limitations of the maximum cable length and number of
possible instruments in the system.
In order to have a properly working system, the voltage drop of every of the
three VDO Bus segments have to be calculated.
1 LEN = 0.05 Ampere
Calculation
12V power supply:
The voltage drop for every segment of the VDO Bus is calculated as follows:
Ohm‘s Law: E (voltage drop) = I (circuit current) x R (wire resistance)
R = 2/2x Cable Length (m) x Power Pair Resistance / 100
L = Total length of VDO Bus cables in one segment
I = LEN (Load Equivalency Number) x 0.050 amps
-> E = 0.05 x LEN x L x 0.057
The voltage drop for each VDO Bus Segment shouldn’t be higher than 3V.
Note
: VDO BUS has 2x AWG 22 Power/Ground cables so there is a different
voltage drop calculation than NMEA 2000.
24V power supply:
If using a 24V system the voltage drop may not be higher than 9V.
Note
: The maximum Number of LEN in the Nav Box system is 120 equals
6 Ampere.
Product
LEN
Nav Control
4
110mm gauge
4
4.3’’ TFT
12
52mm gauge
2
8
