In industrial environments such as automation technology, the control and synchronization of cameras and other components like sensors and actuators is realized by programmable logic controllers (PLC). Here higher switching levels – in comparison with transistor-transistor logic (TTL) – result in a higher electromagnetic noise immunity of both inputs and outputs and thus increase the interference resistance of the whole application.
Switching levels of TTL and PLC:
TTL switching levels
PLC switching levels
2.8 V up to 5.0 V
11.0 V up to 30.0 V
0.8 V up to 2.8 V
4.5 V up to 11.0 V
0.0 V up to 0.8 V
0.0 V up to 4.5 V
On the input side, general purpose I/Os typically come with high levels from 2.8 up to 30.0 V and thus are suitable for the operation in connection with a PLC.
On the output side it is different since the high levels of general purpose I/Os are typically 3.3 V, while PLCs will only detect high level of 11.0 V or more.
GPIO input wiring diagram suitable for direct PLC use
GPIO output wiring diagram not suitable for direct PLC use
DEK-TR/INV (Part Number 2964319) by Phoenix Contact -is a switching amplifier to increase the GPIO’s high level from 3.3 V to a PLC- compliant switching level of 11.0 V or more.
Thanks to the DIN rail design, the module can be clamped between the camera output and PLC input.
The following figure shows the wiring diagram for the switching amplifier DEK-TRI/INV wired to of the GPIO of a Baumer VCXG, VCXU or MXU camera and the digital PLC input.
In this wiring the line inverter of the camera’s output needs to be activated since the output works active-low.
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