Voltage Drop Example 1; Voltage Drop Example 2 - Menvier Security TS2500 Installation & Programming Manual

System Design

Voltage Drop Example 1

Example 1 in the figure below shows two Nodes
connected to the control panel, the first Node is 20
metres from the panel and has 120mA being taken
from its auxiliary supply to power detectors. The second
Node is 20 metres from the first and also has 120mA
being taken from its auxiliary supply to power detectors.
The voltage at each Node is calculated as follows:
1. The total current being drawn at the first Node =
180mA + 180mA = 360mA.
2. Voltage drop to the first Node = 360mA @ 20m =
1.15V (see table).
3. Voltage at first Node = control panel voltage -
voltage drop = 13.60 -1.15 = 12.45V.
4. The total current being drawn at the second Node
= 180mA.
5. Voltage drop to the second Node = 180mA @ 20m
= 0.58 (see table).
6. Voltage at second Node = first Node voltage -
voltage drop = 12.45 - 0.58 = 11.87V.
The example clearly demonstrates that the voltage
levels at both Nodes is acceptable.

Voltage Drop Example 2

The second example shows what happens when a third
Node is connected 20 metres from the second Node.
Example 1
Control Panel
I = 360 mA
A(+)
B(-)
Network
Voltage at panel
13.60 V
Example 2
Control Panel
I = 540 mA
A (+)
B (-)
Network
Voltage at panel
13.60 V
6
20m
Node 1
Node = 60mA
Total = 180mA
AUX
120mA taken by detectors
Voltage at Node
12.45 V
20m
Node 1
Node = 60mA
Total = 180mA
AUX
120mA taken by detectors
Voltage at Node
11.87 V
Figure 1. Voltage Drop Examples 1 & 2
The voltage at each Node is calculated as follows:
1. The total current being drawn at the first Node =
180mA + 180mA +180mA = 540mA.
2. Voltage drop to the first Node = 540mA @ 20m =
1.73V (see table).
3. Voltage at first Node = control panel voltage -
voltage drop = 13.60 -1.73 = 11.87V.
4. The total current being drawn at the second Node
= 180mA + 180mA = 360mA.
5. Voltage drop to the second Node = 360mA @ 20m
= 1.15V (see table).
6. Voltage at second Node = first Node voltage -
voltage drop = 11.87 - 1.15 = 10.77V.
7. The total current being drawn at the third Node =
180mA.
8. Voltage drop to the third Node = 180mA @ 20m =
0.58V (see table 1).
9. Voltage at third Node = second Node voltage -
voltage drop = 10.77 - 0.58 = 10.19V.
The second example demonstrates that when the third
Node is added to the network the current drawn at each
device is increased and therefore the voltage drop at
each device is increased. The voltage level at the third
Node is now below the 10.5V threshold and may cause
problems.
20m
Node 2
I = 180 mA
Node = 60mA
Total = 180mA
AUX
120mA taken by detectors
Voltage at Node
11.87 V
20m
Node 2
I = 360 mA
Node = 60mA
Total = 180mA
AUX
120mA taken by detectors
Voltage at Node
10.77 V
TS2500 Installation Manual
20m
Node 3
I = 180 mA
Node = 60mA
Total = 180mA
AUX
120mA taken by detectors
Voltage at Node
10.19 V