In today's industrial production environment, numerous digital and analog control devices are employed, including motor start-stop controls, solenoid valve activations, product counting, and temperature, pressure, and flow settings. Programmable Logic Controllers (PLCs) have emerged as a highly effective tool to address these automated control challenges.
When designing a PLC control system, several key considerations must be kept in mind:
Firstly, the selection of PLCs and programming devices is crucial. There are many PLC products available in the market, both domestically produced and internationally branded, such as OMRON, MITSUBISHI, FUJI, IDEC, HITACHI, Panasonic from Japan, Siemens from Germany, and LG from South Korea. Choosing the right PLC involves assessing whether the system requires standalone PLC control or networked PLCs. Based on the required number of input/output (I/O) points, calculate the total needed and add a 10% buffer for future scalability.
Secondly, consider the load type. Depending on whether the load is AC or DC, the current demand, and the frequency of operation, decide between relay outputs, transistor outputs, or thyristor outputs. Selecting the appropriate output method ensures stable system performance.
Thirdly, evaluate the execution speed and memory capacity of the PLC. While foreign manufacturers' products are generally comparable, there are subtle differences in speed and capacity, impacting overall cost.
Fourthly, understand the 'COM' points, which vary between different PLC models. Some models offer COM points with fewer output points, while others provide more. This decision impacts how you manage multiple load types and current levels.
Fifthly, ensure compatibility among different PLC products, as full compatibility is rare. Choose products that align with your system requirements.
Sixthly, consider the programming interface. Handheld programmers, graphical programmers, or PC-based software packages each have their advantages and disadvantages regarding efficiency, cost, and ease of use.
Lastly, opt for products from reputable manufacturers known for reliable quality, strong technical support, and excellent after-sales service, facilitating future upgrades.
When designing the input and output circuits, remember the following:
The PLC power supply typically ranges from AC85-240V (or DC24V). To combat interference, incorporate power purification components like filters and transformers. Always check the capacity of the built-in DC24V power supply and implement short-circuit prevention measures.
For external DC24V power supplies, if your inputs require such power and the PLC’s internal supply isn’t sufficient, use an external source. Ensure the external power supply’s ‘one’ end is not connected to the PLC’s DC24V ‘COM’ end to avoid malfunctions.
Input sensitivity must match the PLC’s specifications. Protect against high currents or leakage currents to maintain sensitivity.
Handling inductive loads requires suppressing spikes with suppressors or diodes. Grounding is essential, using a dedicated wire connected to the GR terminal with a resistance below 100Ω. Avoid sharing grounding wires with other equipment.
External drive circuits are sometimes necessary if the PLC cannot directly handle the load. Use relays or thyristor circuits and include protective and surge-absorbing circuits.
For expansion modules, smaller systems (under 80 points) usually don’t require expansion. Larger systems may need additional modules, but be mindful of the manufacturer’s limitations on total I/O points.
Network design for PLCs presents unique challenges compared to standalone controls. Familiarize yourself with the chosen model's instructions, execution speed, memory capacity, communication protocols, and data transfer rates.
Finally, before writing software, thoroughly review the PLC manual. Whether using graphical or text-based programming, always test the program in a simulated environment before deploying it on the actual equipment.
This comprehensive approach ensures robust and reliable PLC control systems tailored to industrial applications.
8P8C (RJ-45) modular jacks (computer networking)
F connector (TV antenna/cable/satellite)
A keystone jack is a standardized snap-in package for mounting a variety of low-voltage electrical jacks or optical connectors into a keystone wall plate, face plate, surface-mount box, or a patch panel.
Many types of jacks are available in the keystone module format, limited mainly by their physical size, including:
8P8C (RJ-45) modular jacks (computer networking)
F connector (TV antenna/cable/satellite)
RCA jacks (audio/video)
4-pin mini-DIN (S-Video jacks)
HDMI jacks (high-definition video and audio)
Optical fiber connectors
BNC connector
4-pin mini-DIN (S-Video jacks)
HDMI jacks (high-definition video and audio)
Optical fiber connectors
BNC connector
With compact size, integral shutter, keystone mounting format a, our keystone Jack for voice and Category 5e and 6A ensure a smart, reliable installation. All copper conductors are plated with gold. The 8 pins of RJ45 tool-less keystone jack are effortlessly terminated in one simple operation resulting in reliable interconnection in record time. The jacks can be reused several times if a wiring mistake is made.
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NINGBO YULIANG TELECOM MUNICATIONS EQUIPMENT CO.,LTD. , https://www.yltelecom.com