Velleman VM122 Mode D'emploi page 7

USAGE AND CONNECTION
Usually the open-collector outputs are used for controlling relays , see fig
1.0 (like our VM129).
Figure 4.0 shows how to connect eventual relays. Its advisable to use a
separate power supply for the relays, rather than to branch off from the
power supply of the receiver.
The 15 outputs of this module are open-collector outputs, which means
they are transistors used as switches. When an output is active, a closed
contact is created between ground (GND) and that output.
As shown in the following connection diagrams, one single power supply
can be used for the receiver module as well as e.g. for the relay switch.
However, separate power supplies reduce the risk of interference.
VM122
VM122
VA
GND
VB
+V
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
+
VCOM
Figure 1.0
Usage and connection
MAINS
MAINS
12V
7