Walkerok

This is an older question but I thought I would respond. Having written mixer programs before this is the method I used to arrive at the correct weight for each batch run. At the beginning of the day the mixer was zeroed. But after that never again. In my process each batch had a recipe of water, gypsum and sand. At the beginning of each batch all that is needed is to look at whatever the mixer has as its weight at the beginning of the batch and look for the difference in weight as the ingredients are being added. A screen shot of a main viewing screen has been attached as an example. In the program you just use the weights as they are at the beginning of each step as the zero point. Keith

It is not possible for anyone to help with your question without knowing what the mechanical components are and how they work. Just an example question ......................... what pumps the fluid? Depending on the answer you have remarkable different solutions to the problem. Just an assumption but a vending machine that needs to meter out a fluid generally will be using a "systolic pump" so for each rotation of the pump a fixed quantity of fluid is dispensed, but non one can guess how fast the rotations will be or how much the pump dispenses in volume per rotation. You have to be much more specific in what you are using and what you are doing. good luck Keith

Sorry, but there are no U90 compatible products that allow multiple serial ports (none that I could find). The original hardware you are using the JZ20-R31 does not have any analog output capability by the way, but to get the IO you need with the communications you need will take you to the V130-33-TA24 and then add either the V100-17-RS4 or the V100-17-RS4X. Thanks Keith

If you go into information mode for the PLC you can get into system settings and go into the system section you should be able to make a PLC change from run to stop or the other way around. However I have never encountered a program where the act of running the program stopped the PC communications, however first time for everything. If you stop the PLC and are able to communicate then the program is what caused your problem. Good Luck Keith

There is nothing pre-built into the PID function block to give you this ability but you can write it for yourself easy enough. You decide when you want to run a PID loop in your ladder. You can suspend a PID whenever your current value is within a dead band you hardcode in the ladder around a set point, or make it settable on a screen. (there is a pause I and D calculations block that will stop calculations for as long as you say. You can stop the entire PID loop when you are within the dead band for a period of time. Your choices as a programmer. Good Luck Keith

So I am sure that some of you may know factoid 2 already but I decided I would share the benefit of lots of testing with everyone. In our products we use the V570, V350 and the JAZZ units to talk to variable speed drives on a regular basis. Most drives come standard with 485 Modbus as the only communications type unless you spend extra money getting optional com cards for the VFD. Two factoids relative to noise. There was a conversation that happened accidentally in the "I have a new project" topic where someone said that Unitronics was very susceptible to noise. Well VFDs make a large amount of noise and it is not always radio noise. A fair amount of the time the noise is actually contained on the local earth to where if you ground the shield of shielded cable you make your noise problem much much worse than in you do not ground your shield. The old conversation about sometimes you have to ground a shield on one end or the other or not at all must be practiced regularly. Factoid 1: I generally would not recommend one brand of product over another but 20 years of use on pressure transducers have shown conclusively that there are definite brands of transducers that work dramatically better than others in noisy conditions. If the noise is radio noise pretty much every transducer is as good as any other. If the noise is carried on the local earth ground of the machinery then really bad things happen on every brand of transducer I have ever used (list to follow) except 1. We have used: Ashcroft Murphy Pepperl & Fuchs GEM WIKA AST Dwyer (all private labeled so there is one that works) and in 100% of the cases when there is a site that has noise infecting the ground because of VFD usage there is a horrible amount of noise created (it has nothing to do with Unitronics) and there is only one cure (separate the sensor from the metal pipe is it screwed into to isolate the sensor from the grounded pipe. If you ever have a site that has what appears to have an incurable noise issue and a VFD is involved unground the sensor and see what happens (pressure sensor just unscrew it and leave is unconnected to anything metal and if your noise issue goes away your grounded piece of equipment is causing your noise issue. So what is the one sensor that seems to be impervious to noise on the grounded pipe? It is specific to exactly one model and one product type only. The SETRA 209 series pressure sensor works perfectly where nothing else will (without lots of noise smoothing). AST is second best (but not as good as the 209 series SETRA) and everything else is just bad. Unfortunately, the 209 series is not NEMA 4 rated and is only suitable to outdoor use with the help of a cover to make a 3R cover. No other model of SETRA transducer works like the 209. Just as a note (if you are not needing Class 1 Division 2) there are companies that make electrically isolated pipe union fittings (for cathodic protection) and we have used these from time to time to help customers through ground noise problems. Factoid 2: It is in the Unitronics documentation but who reads everything (or remembers it over enough time). When connecting to RS485 it is not just important but absolutely imperative that you do not connect wires to pins 2,3,4 and 5. Even if the opposite end is connected to nothing at all (except 1 and 6). What testing has shown is that if any of the other 4 wires touch each other (because you cut them short) they will make an otherwise quite communication line unbelievably noisy. Also even if the ends are not touching the wires themselves act as little antennas and noise becomes worse. How do we know and not guess at this? Because sometimes we try to do what is right and it ends up being horribly wrong. One of our techs went out an sourced a high speed modem cable (shielded with shield all the way up to a metal sheath on the plug). It was not an inexpensive cable and sounded like a really good choice. We were buying 15 foot cables and then cutting this in half to make 2 cables (other devices have screw terminals for their connections and not an RJ12 (RJ12 for RS485 to get all 6 connections) so we would cut away all cables except the two making connection to 1 and 6 at the Unitronics port. We had 70 or so with these cables out and a high percentage of the build had special drain wire considerations that had to be made to make the communication work ok. New project with a different brand of VFD has come along and we build our first three units and zero of them would communicate over 485 communication connection. (we tested everything before build and it worked) WHY? The cable we were using had 4 sets of twisted pairs inside the shield (so two wires were not connected on either end). Testing on a V350 showed that as long as we had a computer connected to port 1 communication between the PLC and the VFD was fast and excellent TX/RX accuracy, but as soon as we disconnect the computer from port 1 communications would fail to a rate of about 75% packet loss (at slowest communication speeds). We tried different grounding of the shield to no effect, we replaced cables (didn't expect that one to work) to no effect, we took the test VFD from our desk and replaced that VFD with one in the constructed panels (no effect), so then just because there was nothing else to try we took one of the connectors that comes in the box for the V100-17-RS4X Modbus adder card and just twisted that to a standard 3 wire Beldon (really poor connection) and communication success went back up to about 99%. So we soldered 3 of the connectors from the V100-17-RS4X and shrink wrapped it all so that we could ship the 3 panels to their end customers. Then began the process of figuring out the whys and wherefores as to what the heck was going on. Taking new (expensive shielded) cable we stripped multiples back all the way to the metal cased plug and found that the manufacturer had done a good job on construction. We removed just the two wires that were not connected to anything on either end and found that removal of the two unconnected wires help com success rise to the 60% level. Then made sure that no wires were touching out of the remaining 4 unconnected wires and coms rose to a 90% success rate. Then we cut the 4 remaining wires to be about 1 inch long and made sure they did not touch anything and coms rose to about 96%. Then made our own cable with an RJ12 connector to have only 2 (totally unshielded wires with low twists per foot) wires and comes were great. So now we will be buying specialty cables that have only the two required conductors inside them. Thank for reading and I hope our pain can save you some. Keith

Everyone has a bad story about every brand of PLC ever offered for sale if you use enough of them. I have had AB, ABB, GE, EZ automation, Automation direct, Moller, Eaton, Schneider, Siemens all fail at one time or another. There are cases where the Unitronic's PLC has frozen or stopped working. I have had failures for water, H2S, lightening, power surges, line slaps, ambient heat, transformer explosions.... Etc. can kill anything. This is all par for the course if you install enough product. After installing upwards of a thousand PLCs (all brands) I can say that I really like the Unitronics PLC and it is dramatically more durable than other lower cost brands. Sgull is exactly correct on the use of AC snubbers and DC diodes and many problems are fixed by adding these to coils and contact closures. Variable speed drives are very electrically noisy and they affect everything on the same ground circuit and close physical proximity. We have 300-400 PLC units (JAZZ, V350 and V570) installed on VFD applications and the most common thing I have to fight on a regular basis is VFD noise messing with the RS232 or RS485 communications. Just like everything else in life sometimes grounding shields is good and sometimes it is bad, but I have never had a Unitronics PLC fail to work at all. Thanks Keith

I am unaware of any pre-built function blocks that will do the cascading you want. You have to write it out long hand in the nets with timers and compare blocks to make the lead lag control you want. Good Luck Keith

if by cascading you mean lead/lag function then there are several ways to do this but one way is: you tell the system to hold a particular pressure. Run pump 1 only ........ if pump 1 has to run greater than 90% of capacity for more than a programed amount of time then bring pump 2 on line to help pump 1. If the combination of pump 1 and 2 runs for less than say 40% of capacity for a programmed amount of time then turn pump 2 off and let lead pump (pump 1) handle all of the load. Automatically switch which pump is the lead pump when both pumps stop to equalize run time. Or automatically switch after a certian amount of time. If switching on the fly, then make sure that lag pump is brought up to speed before shutting down lead pump to smooth out switchover transition. Thanks Keith

+1 for enhanced Vision controllers also. This is really necessary for OEM applications where the same program is used over and over, but the sensor ranges can always be different from one job to the next. I know that the circular guages are not able to do the integer linking now, but this would be an awsome addition. Thanks Keith

I have looked at your file. You are scaling values into the exact same MI locations that you have designated for the thermocouples on the ATC8 module in your hardware setup. Don't do this. The thermocouples do not need any scalling and the values directly off of MIs 200-207. Delete the scaling blocks and look at it again. The information in the MIs 200-207 should be read with one decimal point implied so for example a number of 506 in MI 200 reads 50.6 degrees C based on how you have your hardware programmed in Visilogic. Thanks Keith

For my part I am looking for an enhanced Vision answer to these requests. Thank You Keith

I have a secondary question. I know that I can only have 64 files without the possible corruption of files. In todays technology can't we manage to either allow more files than 64 per folder or at least allow for more than 4 "Excel" folders. We have customers that 64x4 will only allow a customer to have a very short term of SD card data logging. In this case the customer is testing aircraft radiator sections and each and every part must have its own file name so that it can be stored with all of the other required files and paperwork relative to the specific part number tested for tracking. Thanks Keith

I have uploaded a demonstration program on at least one way to show two tank levels in a single tank space they way you want. The program is competely simulated but you will be able to get the idea of what needs to be done. Thanks Keith oil and water tank level simulation.vlp