40
Power supply connections
In the above circumstances, the resistance can be overlooked in the majority of cases. More care must be taken, however, if the cable has to
carry power: in this case, the resistance could cause a signi
fi
cant drop for the purposes of correct operation of the device you intend to power.
Supposing we have a run of 100m of cable powering a device with consumption of 100mA. Using Ohm's Law
1
, let us analyse the voltage drops
for a range of sections:
0.22 mm
2
:
V=R*I = 17*0.1 = 1.7V
0.50 mm
2
:
V=R*I = 6.4*0.1 = 0.64V
0.75 mm
2
:
V=R*I = 5.2*0.1 = 0.52V
1 mm
2
:
V=R*I = 4*0.1 = 0.4V
This is why it is important to size the power supply conductors correctly.
Appendix 3: data network connection cable
To connect the IP module of the S68 switchboard to a data network, you need to go through a hub or a network switch. The switchboard will be
connected by means of a network cable in straight con
fi
guration. In many cases, it will be possible to buy a standard cable of suitable length, but
when this is not possible, you will need to make the connection autonomously.
This is done using UTP CAT5 cable or higher.
The cable will be terminated at both ends with RJ45 plugs with the aid of a speci
fi
c crimp tool. Both RJ45 plugs must be wired in the same
sequence as shown in the
fi
gure.
The conductor colours shown in the
fi
gure must be rigorously observed. Non-conformance with the colours may cause the connection to work
intermittently or not at all.
Procedure:
1. Remove about 5 cm of jacket from the cable so as to make the 4 pairs of wire accessible
2. Separate the conductors in the pairs
3. Stretch the conductors out so as to straighten them, and place them in the order shown in the
fi
gure
4. Adjust the length of the conductors to about 12mm
5. Insert the conductors as shown in the
fi
gure (the connector is illustrated as seen from the side)
1
V = R * I
. The estimated drop in Volts is equal to the total resistance of the circuit, expressed in Ohms, multiplied by the circulating
current I, expressed in amps.
2° edition 07/2014 code 2G40001
178
