There are various series of Siemens PLCs, and the wiring methods may differ depending on the model. In this article, I will focus on the S7-200 series to explain the wiring and power connection details. The S7-200 has different CPU models such as CPU 221, CPU 222, CPU 224, CPU 224XP, and CPU 226, each with its own power supply configuration. Typically, these PLCs use either DC or AC power, and you can usually identify the type by the markings next to the terminal blocks.
When dealing with transistor output PLCs, there are generally two types of input and output configurations: sink-type and source-type. These types determine how the connections should be made, as incorrect polarity can lead to damage or short circuits. Understanding the difference between sink and source is essential for safe and correct wiring.
1. **Sink Input**: In a sink input configuration, the 1M terminal is connected to the negative side (-), and the input signal is connected to the positive (+). This setup allows current to flow from the signal into the PLC.
2. **Source Input**: For a source input, the 1M terminal is connected to the positive side (+), and the input signal is connected to the negative (-). This configuration allows current to flow out of the PLC through the input signal.
3. **Sink Output**: In a sink output configuration, the 1M terminal is connected to the negative (-), the load is connected to the input signal, and the other end of the load is connected to the positive (+). This setup allows the PLC to sink current from the load.
4. **Source Output**: For a source output, the 1M terminal is connected to the negative (-), while the 1L terminal is connected to the positive (+). The input signal is then connected to the load, and the other end of the load is connected to the negative (-). This configuration allows the PLC to source current to the load.
Some models may have common terminals like 1M and 2M that share the same polarity. It's important to check the specific documentation for your PLC model to ensure proper wiring and avoid any potential issues. Always double-check the polarity and connections before powering up the system. Proper wiring not only ensures the correct operation of the PLC but also helps prevent damage to the equipment and potential safety hazards.
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