13
Fieldbus Valve Coupler FD0-VC-Ex4.FF
Product description
Subject to reasonable modifications due to technical advances.
Copyright Fuchs, Printed in Germany
Fuchs Group • Tel.: G49 621 776-0 • USA +1 330 4253555 • Sin65 67799091 • Internet http://www.pepperl-fuchs.com
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4.2.2
Auxiliary valves which can be connected
The valve coupler FD0-VC-Ex4.FF has been designed particularly for intrinsically safe low power auxiliary
valves in 6 V design,
which control the supply of compressed air to the drive
.
The following circuit values are applicable (per channel):
U
S
= 6.4 V ... 7.9 V
I
S
= 1.5 mA (inrush current of the valve)
I
Hold
= 1.0 mA (holding current with the valve switched on)
To switch on, the auxiliary valve is triggered with an increase inrush current I
S
for a short period of time.
Then it is held in its position at the lower holding current I
hold
.
4.2.3
Final position feedback contacts which can be connected
Two final position feedback contacts per valve can be used for detecting the valve positions. These may be
NAMUR proximity sensors or mechanical switches. The binary signals of both PFCs are requested alterna-
tely from the valve trigger equipment in the 2:1 procedure via a pair of cores and must thus be suitable for
this procedure or be provided with a polarised diode (see section 4.2.4).
4.2.4
Description of 2:1 procedure
The 2:1 procedure allows to transfer two independent binary signals to a pair of cores without bus system.
To do so, the two sensors or mechanical contacts are triggered and evaluated in time multiplex mode anti-
parallel (see figure 4.2).
A prerequisite of this procedure is that the sensors/mechanical contacts are provided with a polarised diode
and one of the two sensors/mechanical contacts is operated in polarised mode.
When using NAMUR sen-
sors from Fuchs as PFCs these polarised diodes are integrated. The connection is described in
section 5.4.3.
Do not connect any additional current consumers to the valve circuit (e. g. LEDs).
If additional consumers are connected to the valve circuit, successful operation of
the valve coupler cannot be ensured.
The valve control outputs of the valve coupler can also be checked for correct functioning with-
out connected valves by simulating the valve by a 3 k
Ω
resistor. In deactivated state, via this
resistor a voltage of approx. 0.3 V and in activated state a voltage of approx. 3 V can be
measured. It is not possible to connect a voltmeter direct to the open terminals of the valve
output because then a voltage U
S
of 6.8 V ... 7.4 V is measured independently of the state.
Suitable valves are offered, among others, by Samson, ASCO /Joucomatic and Herion. For
information of suitable valve types please refer to the data sheet and Internet and to
Fuchs.
