DCN4-BR4 Omron, DCN4-BR4 Datasheet - Page 118

• Manufacturer Part Number: DCN4-BR4
• Description: Std. Flat Cbl Branch Line Pres
• Manufacturer: Omron

Specifications of DCN4-BR4

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

3-5-1
Independent Communications and Internal Circuit Power Supplies
Shared Communications and Internal Circuit Power Supply
Step 2: Evaluating the Configuration with Calculations
Formulae for Calculating the Voltage Drop
Note We recommend using separate power supplies for the communications power
Determine the distance between the power supply and each node, and each
node's current consumption for communications. (Refer to the table showing
current consumption for various devices in Appendix C Current Consumption
of DeviceNet Devices.) Evaluate whether the configuration satisfies the for-
mula below. If the voltage drop is within the maximum value indicated, power
can be supplied to the nodes properly with the configuration. Of course the
current cannot exceed the maximum current capacity of the cable (8 A for
thick cable and 3 A for thin cable.)
Formula 1: Calculating the Voltage Drop in the Trunk Line
Ln: The distance between the power supply and node n (not including the
Rc: Maximum cable resistance
Nt: The number of Taps between node n and the power supply
In: The communications current required by node n
and the internal circuit power. (For details, refer to 2-2-9 Sharing the Commu-
nications and Internal Circuit Power Supply.)
The allowed voltage ranges for the communications power supply and internal
circuit power supply are significantly different, as shown below.
Communications power supply voltage range: 11 to 25 V DC
Internal circuit power supply voltage range: 24 V DC +10% to − 15%
The lowest permissible voltage is 11 V DC for the communications power sup-
ply, whereas it is 21 V DC (including the extra margin) for the internal circuit
power supply. If the internal circuit power is supplied by the communications
power supply, the maximum permissible voltage drop due to cable resistance
is much lower than it would be if the power supplies were separate.
When the output voltage fluctuation of the communications power supply is
taken into account and 23 V (the lower end of the fluctuation range) is used as
the power supply output voltage, the maximum permissible voltage drop in a
single power supply line is (23 V − 21 V) /2 = 1 V. The permissible voltage
drop can be subdivided into the max. permissible voltage drop in the trunk line
of 0.65 V and the max. permissible voltage drop in a branch line of 0.35 V.
Determine the distance between the power supply and each node, and the
total current consumption (communications and internal circuit power) for
each node. There’s no need to take into account the internal power supply
current consumption of the Master Unit. (Refer to the table showing current
consumption for various devices in Appendix C Current Consumption of
DeviceNet Devices.)
Evaluate whether the power supply configuration satisfies the formula below.
If the voltage drop is within the maximum value indicated, power can be sup-
plied to the nodes properly with the configuration. Of course the current can-
not exceed the maximum current capacity of the cable (8 A for thick cable and
3 A for thin cable.)
Σ (Ln × Rc + Nt × 0.005) × In ≤ 4.65 V
length of the branch line)
(Thick cable: 0.015 Ω /m, thin cable: 0.069 Ω /m])
(0.005 Ω = The contact resistance of a Tap)
Section 3-5
97