PLC input modules are used to detect incoming field input signal and converts the input signal within the PLC accepts low–voltage signal.
1. Input signal type and voltage selection switch input signal types there are three types of modules: DC input and AC and AC/DC input. General according to the input signal and the surrounding environment when choosing to decide.
AC input module reliable contacts, suitable for the harsh environment of oil mist and dust; short delay time of DC input module can also direct and proximity switches, photoelectric switches, electronic input device is connected.
PLC the switching input module size classification according to the input signal voltage: 5V DC, 24V, 48V, 60V and so on; AC 110V and 220V. Selection should be based on the field input device and input module to determine the distance between. 5V, 12V, 24V for transport distance. Such as: 5V input module must not exceed 10m distance, far higher voltage level of the module should be used.
2. Enter connection mode select input circuit connection of different switching input module can be classified as meeting point–enter both group and input, as shown in Figure 1.
Meeting point–input module input then use a COM port and grouping input module is divided into several groups, one group shared a COM, between each set was separated. Each module grouping input prices higher, if you don’t need to separate between the input signal, you should choose the meeting point.
3. While connected to the number of input points
For selection of high density input modules (32 points, 48 points), should take into account the number of the module and the connected input does not exceed the number 60%.