DS1061-036A
13
The table below illustrates an example of how to calculate the total absorption:
Device
Quantity
Max absorption:
Total
Control panel
1
X
60 mA
=
60 mA
PSTN Communicator
10 mA
=
… mA
GSM Module
30 mA
=
… mA
Speech synthesis
30 mA
=
… mA
Keypads …..
…
X
… mA
=
… mA
Readers
…
X
… mA
=
… mA
Expansion modules
…
X
… mA
=
… mA
IR detectors
…
X
… mA
=
… mA
SUBTOTAL
…
mA
+ 10% for future upgrades
…
mA
TOTAL
… mA
Note
:
▪
Magnetic contacts do not absorb electricity.
▪
The self-powered siren, when it sounds, draws electricity from its own battery.
WARNING!
To not overload the control panel battery, when the mains power supply is absent,
plan to use the self-powered sirens and optical signals (equipped with their own battery).
2.4
CABLE DIMENSIONING AND POSITIONING
2.4.1 Dimensioning
The cable cross section must be calculated considering the most critical system power supply condition,
equivalent to mains fail and backup battery just over the “flat battery” level (11.2 Vdc).
For example, if at full load conditions, on all the devices power supply terminals must be ensured at least
10.5 Vdc, the maximum voltage dropout admitted on the cables is 0.7 Vdc.
The calculation formula is:
V
c
= 2 x length x R
m
x I
d
where:
V
c
is the voltage dropout in Volt
length
is the cable length, in metres (single wire)
R
m
is the cable resistance in Ohm/m
I
d
is the current required by the devices, in Ampere (value obtained by their technical sheets)
The values of copper cable resistance are:
Cross section – mm
2
0.22 0.50 0.75 1.00 1.50
Resistance – Ohm/m
0.0795 0.0350 0.0233 0.0175 0.0117
