Technical background
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:
State | TTL switching levels | PLC switching levels |
High | 2.8 V up to 5.0 V | 11.0 V up to 30.0 V |
Forbidden zone | 0.8 V up to 2.8 V | 4.5 V up to 11.0 V |
Low | 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 wiring diagrams
GPIO input wiring diagram suitable for direct PLC use
GPIO output wiring diagram not suitable for direct PLC use
Remedy
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.
Support
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