I'm currently working on a project involving a master PLC with slave definitions for 10 different slaves. My task is to replicate these 10 slaves using a PLC. I initially chose the Productivity 1000 PLC with a P1-540 CPU, but encountered two issues. Firstly, the Productivity PLC only supports 2 node addresses, limiting me to emulating only 2 of the required slaves. Secondly, all the slaves are the same model, which means writing to change a parameter affects all slaves. This poses a challenge as the Productivity PLC has a single address set, causing operations for different slaves to target the same address. If anyone has suggestions on how to address this issue, such as using an intermediary solution between these two PLCs or recommending a different PLC model that can resolve this problem, I would greatly appreciate it. Master PLC slave definitions example: Slave 1 - Slave ID 1 - Tagname: tag1 - Address: 2 - Action: Write - Operation: Write Multiple Registers (16) - Tagname: tag2 - Address: 0 - Action: Read - Operation: Read Input Registers (4) Slave 2 - Slave ID 2 - Tagname: tag3 - Address: 2 - Action: Write - Operation: Write Multiple Registers (16) - Tagname: tag4 - Address: 0 - Action: Read - Operation: Read Input Registers (4) Slave 3 - Slave ID 3 - Tagname: tag5 - Address: 2 - Action: Write - Operation: Write Multiple Registers (16) - Tagname: tag6 - Address: 0 - Action: Read - Operation: Read Input Registers (4) And so forth...
When deciding between using Modbus TCP or Modbus RTU, it is important to consider the limitations of built-in Modbus Server instructions in PLCs. One possible solution is to use five PLCs with two Slave IDs each to emulate 10 nodes. Alternatively, you could develop a custom Modbus Server capable of handling 10 slave IDs and mapping addresses for each ID to unique areas. This approach allows for greater flexibility and customization in your Modbus network setup.
Based on your description, it seems that you may want to consider using a PLC like the Siemens S7-1200 series that supports up to 248 nodes, and they also allow each node to have its own unique tag set. This would allow you to emulate all your 10 slaves and manage the parameters independently for each of them. You may also want to employ some form of Fieldbus technology (like a Profinet network), which can help increase the efficiency and specificity of your commands between the master and slave devices. This approach will avoid that global parameter issue you're experiencing now. Of course, the cost, size, and complexity of your project should dictate whether this solution is feasible or not.
It seems like the Productivity 1000 PLC may not be an ideal choice given its limitations in supporting multiple node addresses for your scenario. You could consider PLCs from other brands like Siemens, which have models that can support greater number of nodes. Another option would be to use an intermediary device such as a Modbus gateway that can simulate more node addresses than your PLC, but this adds additional complexity and potential points of failure. Alternatively, in some PLCs, you could utilize the concept of virtual nodes or virtual PLCs to simulate your slaves. Remember to make sure whichever route you go, your solution must be able to handle concurrent transactions as you're dealing with multiple slaves here.
From your explanation, it looks like the major issue you're facing is with the limited number of node addresses that the Productivity 1000 PLC provides, which is inadequate for efficiently emulating all 10 slaves you have in your system. One solution might be to consider using a different PLC that supports the extensive number of nodes you require. Siemens' PLCs, for example, have been noted for their high node support and could be a good fit. In the event that hardware change isn't an option, one workaround might be to employ a network gateway or communication server. This would act as an intermediary between your Master PLC and the Slaves, distributing the tasks as needed. It's sort of like adding an additional layer to your control system, but it might just provide the flexibility you need to get around the limitations of your current PLC.
You might want to explore a couple of different approaches to navigate around this challenge. One solution could be to use multiple Productivity 1000 PLCs, with each emulating a subset of the slaves, but then you'd need a manager PLC to control and coordinate data between these multiple PLCs, which can complicate the program. Alternatively, given your specific needs, consider using a PLC that supports a larger number of node addresses and allows individual targeting for each slave. The Siemens S7-1200 PLC, for example, offers dynamic addressing and high scalability in node management. However, switching PLC models would require some adjustment to your programming and could imply additional costs. Yet another option could be looking at FieldServer protocol gateways, which effectively handle translation between different nodes and protocols, which could help streamline communication between your master and slave devices. As always, evaluate these suggestions in line with your project's specific needs, constraints, and budget.
It sounds like you're facing a pretty tricky challenge with the Productivity 1000 PLC’s limitation on node addresses. If you haven't already, consider looking into a different PLC brand that supports more node addresses and better parameter management for multiple similar slaves—like the Siemens S7-1200 or the Allen-Bradley CompactLogix, as they tend to offer more flexibility with Modbus communications. Additionally, implementing a gateway or an intermediary device could help manage communication between your master PLC and the slaves, allowing for unique addressing on the slave devices and possibly alleviating the constraint you're encountering. Good luck with your project!
It sounds like you're running into a pretty common limitation with that PLC setup. One possible solution could be to consider using a different PLC model that supports more node addresses, like the Allen-Bradley Micro850 series or the Siemens S7-1200, both of which can handle multiple slaves and have more flexibility in addressing. Alternatively, you could implement a gateway or intermediary device to manage the communications, allowing you to expand the number of nodes while keeping your master PLC. This way, you can handle the slave configurations more effectively without running into address conflicts. Good luck!
✅ Work Order Management
✅ Asset Tracking
✅ Preventive Maintenance
✅ Inspection Report
We have received your information. We will share Schedule Demo details on your Mail Id.
Answer: The limitations include constraints on the number of node addresses supported by the PLC, which can restrict the number of slaves that can be emulated, and challenges in managing multiple identical slaves due to a single address set.
Answer: The Productivity 1000 PLC with a P1-540 CPU was chosen, but it only supports 2 node addresses, limiting the emulation to just 2 out of the required 10 slaves.
Answer: Having all the slaves as the same model means that changes made to a parameter will affect all the slaves, which can complicate operations as the PLC has a single address set.
Answer: Suggestions include exploring intermediary solutions between PLCs or considering alternative PLC models that can support a higher number of node addresses to accommodate the required number of slaves effectively.
Join hundreds of satisfied customers who have transformed their maintenance processes.
Sign up today and start optimizing your workflow.