Yaskawa 260IF DeviceNet System - Manual (Page 80)

7.1 Wiring Communications Power Supply
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Find the distance between the power supply and each node and the current consumption
for each node in the communications section. If the following conditional expression is
met, the power supply specifications for each node are met.
Conditional expression: Σ (Ln × Rc + Nt × 0.005) × In ≤ 4.65 V
• Ln: Distance between power supply and node (not including the length of the drop
line)
• Rc: Max. cable resistance (0.015 Ω /m for thick cables, 0.069 Ω/m for thin cables)
• Nt: Number of Adapters between each node and the power supply
• In: Required current consumption for each node’s communications section
• 0.005
Ω = Adapter contact resistance
Make sure that the maximum current capacity for the cable is not exceeded (8 A for
thick cables, 3 A for thin cables).
2. Shared Communications and Internal Circuit Power Supplies
Wherever possible, avoid using the same power supply for both communications and
internal circuit power because the allowable voltage ranges for communications and the
internal circuit power supplies differ, as shown below.
• Allowable voltage range for communications power supply:
11 to 25 VDC
• Allowable voltage range for internal circuit power supply:
24 VDC +10%/ –15%
Find the distance between each node and the power supply and the total current con-
sumption for the communications and intenal circuit power supply sections of each
node.
If the following conditional expression is met, the power supply specifications for each
node are met.
Conditional expression: Σ [(Ln × Rc + Nt × 0.005) × In] ≤ 0.65 V
• Ln: Distance between power supply and node (not including the length of the drop
line)
• Rc: Max. cable resistance (0.015 Ω /m for thick cables, 0.069 Ω/m for thin cables)
• Nt: Number of Adapters between each node and the power supply
• In: Required current consumption for each node’s communications and internal cir-
cuit sections
• 0.005 Ω = Adapter contact resistance
Make sure that the maximum current capacity for the cable is not exceeded (8 A for
thick cables, 3 A for thin cables).
Countermeasures
If the conditional expression is not met, consider using one of the following countermea-
sures.