Simon
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Posts posted by Simon
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Unitronics does not require output conditions to be in parallel. This is different to "traditional" ladder logic. Of course it is fine if you want to put the output coils in parallel, but that will have no effect on the function of the program.
When you get the error9 does that only happen for a download, or when you save the file? You must save the file to a fixed harddisk on the computer. It will not play nicely with a network drive or removable drive.
What type of serial port are you using - USB dongle or direct RS232?
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Hi,
If I have understood correctly, you have a couple of options, all of which involve some legwork, but will give you the results you need.
1. Get some wires and apply 24V to the inputs you need to activate.
2. Modify the program and put an MB contact in parallel with each the physical input contacts. Then you can manually toggle the MB values to simlulate inputs changing. Save a copy of the original program before making the changes.
If events happen too fast to see, you may also need to add math functions to increment a register each time the event occurs, so you know it happened.
I hope this helps.
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Yes, it is possible to send integers in a text message. Just note that when sending you need to put a '#' either side of each variables. Eg to send 123 and 456 it should be #123# and #456#. This is in the help file.
Also use leading zeros on the variables to make them always the same length.
Finally, the specification for SMS is for delivery within 24hours. Usually it is much faster than that, but sometimes they have a long delay. You should allow for this, for example your recieving PLC could have a watchog timer that sets the outputs to a safe value if the time between messages was too long.
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There are two aspects to this that must both be solved.
1. Comms from the PLC into the modem and control of the connection.
This should be possible of you use a modem that is capable of scripting, since the Jazz/M91 cannot control the GPRS functions themselves. So the modem must handle all aspects of the connection, and when finished the sign-on process it is just a serial "pipe" onto the GPRS network. I have worked with a customer who uses an M91 connected to a GPRS/3G serial modem this way. In his case, however, the end-point is a computer server connected to the internet, not another PLC connected to a modem.
2. Linking of the IP address of one modem to the other
This is more difficult. Most cellular providers give out private, dynamic IP addresses. These are almost useless for the type of application you are proposing. They can be made to work if you have an external server and set up a VPN. If you can get a public, dynamic IP address then you can use an external service like dyn.com to link them by resolving domain names. The easiest setup is to use public, static IP addresses, but they are hard or impossible to get for a cellular service. Based on the method used to link the IP addresses, then the serial data can be streamed between the two modems.
In practical terms, I think it would be almost impossible if you just wanted two modems to talk over GPRS without the involvement of an external server.
However I am keen to learn more if there is a way.
How fast does the update rate need to be? Can you achieve your result using text messages?
How far apart are the devices? Could you use a dedicated serial data radio instead?
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I would recommend the webinars:
http://www.unitronics.com/Content.aspx?page=webinars
I was talking to a customer yesterday who shared a similar experience to you of trying to pick up the programming by reading help files. We all learn in different ways. The webinars give a richer experience, so hopefully you get a better idea of how it fits together.
You can also look at the program examples that are supplied with the Visilogic installation - see "Help" -> "Examples..."
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This is just a maybe, but the RS485 to Ethernet converter may be responsible for the delay.
Is there an option to install CAN bus cable and network the PLCs with CAN? By connecting the first PLC on ethernet, it can also be the bridge between ethernet and the CAN network, and this is quite fast.
I hope this helps.
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It could be possible to use a 2-pair cable. The minimum standard would be twisted pairs, and It would work best if the pairs were also individually shielded. Use the lowest baud rate possible on the Modbus, and highest possible for Remote Operator.
Regarding the speed of Remote Operator, is this just when you are connected to a single PLC? What baud rate are you using? Do you have temination active on the first and last PLCs in the network?
If everything is working properly, you should get a fast response with just one PLC, similar to the speed when using the RS232 programming cable.
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For some reason this topic was marked as unread, so I read it again. :-)
If I understand correctly, the on-site PC is already running Remote Operator. Another option is to use a remote terminal application (like VNC) to allow external users access to the on-site PC, so they look at its Remote Operator screen rather than connect directly to the PLC. I know VNC allows multiple connections, and I would expect a PC to have more resources for multiple connections than a PLC.
This might be too late for the original app, but maybe it helps someone.
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Hi,
Unfortunately the traffic from the Remote Operator will conflict with the Modbus communications.
*Maybe* you might get some kind of success if you set the Modbus poll rate to be as slow as possible, but even so, you would see a lot of retries on both Remote Operator and Modbus. This would not be robust, but may get you out of trouble.
A full solution would only be possible if you set up a separate network using the second port on each PLC, as you originally intended. If cabling is a major obstacle, the Unitronics work very well over wireless telemetry data radios. I would use the Radios for Modbus and use the existing cable for Remote Operator, since Modbus uses relatively short packets, with more control over the polling rate.
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Hi Ron,
Based on my knowledge of the topic, I agree with Denis regarding the general configuration. However you are potentially left exposed to liability if you don't consult a qualified Hazardous Area specialist. The extent of this depends on the legal situation in your country. You could be prosecuted just for installing something without proper certification. If there was an incident, then they can really throw the book at you, even if your equipment did not cause the problem. Being able to say you discussed the issue on the Unitronics forum is far from an adequate defence.
There are no doubt many installations out there that don't comply with standards, but are technically safe, and probably many that are not safe. The fact that these haven't casued an explosion (yet) is not a reason to disregard due caution.
The first thing you need is the hazardous area classification. At the very least this needs to be done by a trained person, preferrably paid for directly by the end-user (either a direct employee with the relevant qualifications or a paid consultant).
I hope this doesn't come across as overly alarmist, and at the end of the day, this has very little to do with me. However the photos I have seen of sites that have been levelled by exposions speak for themselves. The consequences are rare, but catastrophic.
If I was in your position I would take all possible steps to get it right and also be able to prove that I took these steps.
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I would get involved directly with someone who has qualifications in the field of hazardous areas. Firstly you want to be sure the design is going to be safe. Secondly you want to be sure no-one is going to blame your equipment if there is an incident.
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The U90 Ladder software is able to copy the program from the Jazz back to the PC to view and edit the ladder. Use the "upload" option from the "controller" menu. You will need a JZ-PRG communications adaptor if one is not already fitted into the PLC.
As you have mentioned, if the program is password protected, you will need to enter the password to upload.
It is also possible to disable the project upload feature when the project is downloaded to the PLC. If this was done, then it is not possible to upload the project at all, and the software will give an error message.
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If the device is vivible (you have a public IP) then you should be able to access it from any internet-connected PC, just by putting its IP address and PLC name into Visilogic. However, it is unlikely that IP address of the PLC will be public, unless you have gone to some trouble to set it up that way.
Can you clarify how the PLC is connected to the internet?
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Hi Joe,
I think the term "going birko" could describe your state of mind. I am unsure of the history of that term, but there is a brand of electric urns (protable water heater) called Birko, so imaging one of those with the thermostat stuck on, boling like cray and steam flying out.
Good point about the slaves receiving data and that then triggering an event to send the data back out. I guess you could interlock the send activity with a touchscreen bit, so it only sent if the changes was in conjunction with touchscreen activity.
As you say, it would be handy to have a "best practice" example of how to do this.
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Hi TIm,
What do you mean by "I can reach the internet but the LAN servers are off limits"
What ISP are you using to access the internet?
I recommend people use the SMTP server that belongs to their ISP. Other servers can sometimes work, but this seems the safest bet. Someone got this working recently based on that advice. But as I said to them, this is determined by forces outside our control.
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I am currently working on an application with a main Unitronics PLC and a single slave Unitronics PLC. The slave is mainly an HMI slave. So this issue has been fresh in my mind, as it still is relevant even in the case of only two devices.
It sounds like you are transmitting the data cyclically, which would be necessary if you were using a strict master/slave protocol like Modbus. Even with two devices, this raises the question of who gets the data first, the master or the slave?
However with UniCAN, the programming can be more like a peer to peer architecture.
I would suggest an event-driven approach, at least in regard to the human input data. So you only transmit data to the all the PLCs if someone makes a change on one of the screens. This is similar to the way the EX-RC1 example program is written. There can still be a small chance of conflct if two people happen to try making changes to the same object at the same time on different screens. But, since UniCAN can be quite fast, the chances are small.
If you really want it bullet proof, I would probably go with an explicit "token passing" structure. That is, the user has to request control at a particular station before being able to change data. While the user has control at that station, all others are locked out of edit mode, but still receive updates of the data.
I hope this helps.
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Just a further note, so the trend data is stored in a "closed" format, you can't access it as general data from within the ladder. It can only be accessed via the trend HMI object or by saving to SD card.
If you also want to see and manipulate the data from inside the ladder, it is not a big deal to add a Data Table as well. So you run the trend and the write to the data table simultaneously, logging the same data to both. Of course with the data table you can also log additional data that you may not wish to include in the trend.
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Here's one I prepared earlier, for 13-bit code. Hopefully it is clear enough to understand how to use for 9-bit.
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With the structure you propose CAN ISC will be a simple solution.
Note that ISC is a cyclic communication:
When the data in these operands is constant (unchanging), it is broadcast every 400mS. When the data is dynamic (changing) it is broadcast at a rate not exceeding 20mS. Even when the data changes are rapid, data is not broadcast at a rate exceeding 20mS; this avoids network overload.You are effectively treating the slave HMI like a remote I/O block, by using a separate block of registers for "in" and "out". I have thought through another situation where the slave is more tightly integrated and writes directly back to the active registers in the master program. In both cases it is necessary to consider the flow of data between the master and slave. If either master or slave can control the system, it is essential to make sure they are both operating on the most up-to-date data, and that edits on one side are not overwritten with old data from the other side.
It seems to me that either:
1. you use CAN ISC and write code in the master (and/or slave) that ensures the consistency of the data. This means controlling when the data is read to or written from the CAN ISC registers.
2. You use UniCAN and only send data in either direction if there is a change.
So, for a simple system as you describe I think CAN ISC will be fine, and the logic to ensure no data conflict will be reletively simple.
However for a more complex system, it may be an advatange to use UniCAN, and a commuincation structure similar to that used with the EX-RC1 expansion module.
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This topic has been of interest to me for some time, and I am currenttly helping a customer with a similar application.
Firstly there is no built-in HMI mirror function. This capability needs to be done manually in the program, however it is not so difficult.
I suggest using CAN as the physical layer. Unitronics have some nice features in CAN that will assist:
- UniCAN protocol, which is fast and allows event-driven communications from both ends (compared with the polling that would be required for Modbus).
- Programming pass-through, so you can program both PLCs by connecting into one of them.
You can export HMI screens from the original program to help create the slave, which can save you the trouble of re-laying the screens from scratch.
I hope this helps,
- UniCAN protocol, which is fast and allows event-driven communications from both ends (compared with the polling that would be required for Modbus).
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Aha, now it makes sense, I thought maybe you had forgotten to attach the photo.
It is quite OK to include the image with your original post, as I have done with my reply to that post.
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I was thinking, could Unitronics form a partnership with an existing producer of power analysers? I think there are even several such companies in Israel.
In this case, Unitronics could purchase or license the design for the meter circuit, and add the expansion I/O interface on the front-end. Then put in in a Unitronics expansion module housing.
This is still not a trivial task, but much less costly than developing from scratch.
If such a module could be built into the Jazz as an I/O board, then it's not hard to see where 200-300 per year could be used. I suppose end-user pricing around the $500 mark would be on target.
How many power meters allow you to plug in a modem and support user-configurable SMS? With a Jazz solution we have local control, I/O and also communictions options to allow central data collection or SMS alarming.
When I say I can see the potential it is because this is an area that no-one has cared about in the past, but with the introduction of carbon trading and concerns over energy usage, industrial and commercial customers now want to know much more detail about where their energy is being used. It's not good enough to have just one power meter at the front gate, they want to put them in different parts of the plant. The Australian Govenrment pays special subsidies for businesses who reduce their energy usage. They can only claim these if they prove the energy reductions, which they can only do if they install local metering. I presume other governments do the same, or will be doing this in future.
Whether or not one believes in carbon trading as a solution, energy efficiency and concerns over declining resources are still going to drive demand for this type of product.
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Also check the power supply wiring - you need to feed in 24V on the analogue ouput connector to power all the analogue circuitry (0V and VA terminals).
Also double check the analogue input wiring, note the shared common and make sure your input comes in on the T+/PT/AN terminal.
I think that is it for the more obvious points.
IO-LC3 specification clarification
in Vision & Samba PLC + HMI Controllers & VisiLogic Software
Posted
Hi Damian,
My answer is no substitute for the wisdom of the creators, however I would suggest the specs on settling time are to be taken at face value.
If you want speed, then multiple LC1 modules sounds like the way to go.
I suspect that in the IO-LC3 the A/D convertor is multiplexed to the loadcell signals. When only one signal is active, it is fed directly to the convertor. When 2 or 3 are active, the multiplexer comes into play and there must be extra time between each sample for the old signal to be cleared and the new signal to settle (think about capacitance and high-impedance circuits).
(I have seen a similar spec like this with a small Allen-Bradley PLC. Our customer added a second analogue sensor to the PLC and configured a second input on the PLC to read it. Following that we got a call to say our sensor was too slow. It turned out the analogue input sample time of the PLC increased dramtically when the second input was configured. I think it also had something to do with one input being 0...10V and the other 4...20mA.)
As for filter and settling time.
1. the slower sample rate will mean much fewer values to work with. So if the base sample period is 675ms, you should expect strange results if you settling time is less than this value, and it probably should be 5-10 times the sample time.
2. I don't think the statement about independent setting of the filter parameters conflicts with the statement about the interaction between base sample time and filter depth. It just means that once you take account of the slower sample rate and how it will affect your filter times, you can still set different filters. For example one settline time can be 5 times the sample time, and the other can be 10 times the sample time.
I hope this helps.