99
Step 2: Evaluating the Configuration with Calculations
Section 3-5
Group 3:(30
×
0.015 + 3
×
0.005)
×
0.30 = 0.1395 V
Group 4:(40
×
0.015 + 4
×
0.005)
×
0.15 = 0.093 V
Total voltage drop = 0.0039 + 0.0651 + 0.1395 + 0.093 = 0.3015 V
≤
4.65 V
In this case, formula 1 is satisfied, so the power supply can supply just the
communications power.
2.
Calculate the voltage drop when the communications power supply pro-
vides both communications power and internal circuit power (formula 2.)
Group 1:(1
×
0.015 + 1
×
0.005)
×
0.545 = 0.0109 V
Group 2:(20
×
0.015 + 2
×
0.005)
×
0.84 = 0.2604 V
Group 3:(30
×
0.015 + 3
×
0.005)
×
1.1 = 0.5115 V
Group 4:(40
×
0.015 + 4
×
0.005)
×
0.85 = 0.527 V
Total voltage drop = 0.0109 + 0.2604 + 0.5115 + 0.527 = 1.3098 V
≥
0.65 V
In this case, formula 2 is not satisfied, so the power supply cannot supply
the communications power and internal circuit power.
Example Configuration 2
In this example, the power supply is near the middle of the trunk line. The
trunk line is thick cable and the branch lines are thin cable.
1.
Calculate the voltage drop when the communications power supply pro-
vides communications power only (formula 1.)
a) System 1 (Left Side)
Group 1:(20
×
0.015 + 2
×
0.005)
×
0.255 = 0.0791 V
Group 2:(10
×
0.015 + 1
×
0.005)
×
0.3 = 0.0465 V
Total voltage drop = 0.0791 + 0.0465 = 0.1256 V
≤
4.65 V
In this case, formula 1 is satisfied on the left side.
b) System 2 (Right Side)
Group 3:(10
×
0.015 + 1
×
0.005)
×
0.15 = 0.0233 V
Group 4:(30
×
0.015 + 2
×
0.005)
×
0.15 = 0.069 V
Total voltage drop = 0.0233 + 0.069 = 0.0923 V
≤
4.65 V
In this case, formula 1 is satisfied on the right side.
2.
Calculate the voltage drop when the communications power supply pro-
vides both communications power and internal circuit power (formula 2.)
a) System 1 (Left Side)
.
.
.
20 m
10 m
10 m
30 m
.
.
.
.
.
.
.
.
.
Group 1
45 mA + 30 mA
×
7 = 255 mA
90 mA
×
7 = 630 mA
Group 2
30 mA
×
10 = 300 mA
80 mA
×
10 = 800 mA
Group 3
30 mA
×
5 = 150 mA
70 mA
×
5 = 350 mA
Group 4
30 mA
×
5 = 150 mA
140 mA
×
5 = 700 mA
Power
Supply
Node
Terminating
Resistor
Node
Terminating
Resistor
Trunk line:
Thick cable
Node
Node
Node
Node
Master
16-point
Input Unit
16-point
Input Unit
16-point
Input Unit
Branch lines:
Thin cable
5
Units
4-point Analog
Input Unit
4-point Analog
Input Unit
4-point Analog
Input Unit
16-point
Output Unit
16-point
Output Unit
5
Units
10
Units
7
Units
System 1
System 2
Node
Node
Node
Node
Node
Node
2-point Analog
Output Unit
2-point Analog
Output Unit
2-point Analog
Output Unit
Summary of Contents for DEVICENET -
Page 1: ...DeviceNet Cat No W267 E1 11 OPERATION MANUAL...
Page 2: ...DeviceNet Operation Manual Revised April 2008...
Page 3: ...iv...
Page 5: ...vi...
Page 7: ...viii...
Page 9: ...x...
Page 13: ...xiv...
Page 41: ...20 Basic Operating Procedures Section 1 4...
Page 107: ...86 Operational Checklist Section 2 6...
Page 123: ...102 Step 3 Splitting the System into Multiple Power Supplies Section 3 6...
Page 161: ...140 Index...