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bobnorway

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bobnorway last won the day on February 22 2019

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  1. add the values from first byte to the last byte to the sum. (1+2) H0b + H00 = H0b (S+3) H0b + H01 = H0c (S+4) H0c + H00 = H0c (S+5) H0c + H00 = H0c (S+6) H0c + H00 = H0c (S+7) H0c + H00 = H0c (S+8) H0c + H00 = H0c (S+FF) H0c + Hff = H0c mask off values larger than one byte) (S xor 3c) H0c xor H3c = H30 The H3c is probably to ensure that the check sum which is the last byte is not zero
  2. PLC PID is a mathmatic function not hardware based. Most PLC PID implementations are for regulation 0 - 100%, or reverse for cooling. 100% of 'what' to do 'something' is not realy their bussiness. This makes the PID function "universal". It is your job to scale the "footballs per day " PID input to 0-100%, and then scale the PID output from 0-100% to "footballs". In your case with the PID output do a simple scaling (PIDX * 2) = 0-200% then subtract (PID2X -100) gives a range of -100 to +100 have a good day.
  3. We had a similar problem a while back and ended up puting an optical isolator between the sensor and the Unitronics.
  4. I whole heartedly agree with "almost never", but as the saying goes "never say never" When working with most sensor devices you have a finite range 0-20ma = 0-100% or 0-10bar or 0-12feet using whole number math insulates you from idiot number results like a 1234% full tank, it simply can't happen. However you are trying to average positive and negative numbers, this would be a good place to have an exception to the rule of thumb and use real numbers. In "the old days" plc's could not handle real numbers well and used a long, long time to calculate them this gave long CPU cycle times and not particularily good results. Todays plc's have much better cpu's and can handle real numbers pretty well. We are never trying to calculate the budgjet deficite of a world economy so 8 significant places is good enough for us in real life usage. Unitronics scaling is really easy min - max what you get input to min - max what you want output. I would like to suggest that you filter out the unresonable values given by the arm passing in front. If input > 123456 mm then goto end run your stacked array average only with ok numbers. "garbage in garbage out"
  5. Standards Once apon a time in the 'good old days' there was a standard to ease interfacing of different equipment together. It was called 'RS-232' for simple and effective serial interfacing. The voltage was a given always a -12 to +12 volt swing, a safe voltage with reasonable noise immunity. Then one fine day in order to reduce parts count it was implemented as 0 to +12 volt. Still almost as good and cheaper. As terminals became PC's the parts count was reduced so the readily available 0 to +5 volt was used as a power source. Not quite as good but even less expensive. The lower voltage allowed for a higher communication speed. Sometimes one end of the Com line was one type and the other was a different type. This lead to problems but neither end manufacturer was 'responsible' so it continued on. The Standard called for a 25 pin 'D' sub connector allowing for plenty of future space. This configuration gave full hardware hand shaking, these hardware lines could be tied up or down to reduce the parts count. Tied lines were not as good but are even less expensive. With the reduced pin count it was possible to use a 9 pin 'D' sub connector. This reduced cost and space requirements. Luckily throughout all of this development there has always remained a 'constant' which is one 'transmit', one 'receive' and one 'ground' pin. Within the Standard 25 pin version pin 2 TX, 3 RX, 7 Gnd are used. Of course the Standard 9 pin version is different 2 RX, 3 TX, 5 Gnd. The 6 additional handshaking lines are also moved around. These are the 'Terminal' standards, the other end is a 'Modem' standard with the functions of pin 2 and 3 reversed. Naturally if it is for a PC to PC Com line this will not work and the infamous 'Null Modem' crossed cable is used. PC's are often supplied with male connectors which may require a female - female adapter. Often a male - male adapter will also be necessary and a 25 to 9 pin adapter is very usefull to complete the connection. A break out box is a very handy tool allowing individual pins to crossed as required until the connection works. In real life sometimes one or more of the pins are accidentally left floating this gives all sorts of intermittant trouble. Grounding two electrical machines together via the serial connector sometimes produces a ground loop which plays havoc with the system. To avoid this danger some manufactures don't connect the ground pin to the chassis! The original 'standard' had a cable shielding connection to the connecter shell but inexpensive connectors made of plastic defeated this function. So the 'RS-232' Standard implementation can be 25 or 9 pin, male or female, 12 or 5 volt, send or receive function, handshake or not, grounded or isolated. I should mention 'Standard' speeds, baud rate (bit) 50 and upwards, Mark and Space (1 and 0), Start and Stop bits, 5 to 16 bit per character, ' Standard' character coding, check sum controls, Com protocols, point to point or multi drop. So it may take a while to get a 'Standard' system online. a good read http://www.machine-information-systems.com/RS232_Pinouts.html and also https://en.wikipedia.org/wiki/RS-232 Regards Bob Clarke
  6. Not to discourage you but your task is difficult. RS-485 is a "recomended standard" it comes in both 2 and 4 wire versions. Mixing different suppliers, hardware interfaces, software protocols, all at once will be a challenge. Things like a the standard definition of high byte low byte position, and starting count position, is 4000 or 4001 the first byte? Neither Siemens nor Unitronics are "True" Modbus followers. Read up on what Modbus should be and what the supplier has actually implemented. All of these problems must be overcome before your own control logic can be effective. I would strongly suggest you break the problem down into solvable portions. Get the RS485 hardware right first and then get the Modbus to Modbus protocol right independantly for each supplier. The quickest and best way is using something which has been proven to work. Use Siemens to Siemens and then Unitronics to Unitronics to solve some commumication without to many unknown factors.. Use a Modbus analyser to debug and see what is 'really' going on. Polling requires that communications both ways is correct. Watching a cyclic broadcast will be simpler to start with. Then when you finally have a feel for this you can hook the two different systems together and tweak it up. Good luck
  7. a good rule is to make your pulse to a flag bit, Px -> M123 then the flag M123 will be the same for all of your program code. using a frequency function several places in the code could be a problem because it is asynchronous and can change during your program execution.
  8. heres a quick example of what I ment packing bits, the bit order does not have to be contigious It should be flexible enough so you can get something done. Test_Bits.ulpr
  9. perhaps by packing 8 or 16 or 32 bits to an uint then store a copy and compare with it. any value change can then trigger an unpack rutine to identify which bit changed.
  10. There is NO! warning given that updating pc software from 1.25 to 1.28 requires a re-load of the plc! A quick program change for me has evolved to an hour long hasle with: (1) ethernet cable no connection!, (2) usb cable no connection, (3) then to usb memory stick! First by pc programming a memory stick then plc programming from uniapps takes time! And if I didn't happen to find a 'correct' stick to do this with in my bag? Dear Unitronics the plc control is serious business! Damaging the customers production line costs money! You can NOT play with systems in this way! Any software version change which is so serious must be preceeded by a clear warning. Bob Clarke
  11. check your grounding, analog inputs don't tolerate much common mode offset. the fluctuating siganal could be routed near a noisy source, for example a VFD motor. temporarily switch the two and see if the problem follows the sensor.
  12. I use only two symbols to build a valve being either light or dark (red or green) whatever you like then dynamicaly activate to show as on or off. By aranging several of these (like a clover leaf) you can easily make all the various valve types, one way, two way, 3 way etc.
  13. I quite agree on the PDF as absolutley the most usefull format, no argument there. However my problem is that in many cases the resulting PDF is unreadable. Failing on pagination for longer functions and on width for more complex ladder statements. The is no title field nor any page numbering to pull it all together. I would love to see some way to insert a formfeed in the code giving me a clear sectioning of functions. The poster option doesn't really help all that much and results in something impossible to use in a binder notebook. It may well be that Adobe is not helping much here but it actually can't change the source file.
  14. I think that Unitronics should put some real effort into this. Good documentation is a major part of good programming. Some control over boarders (top, bottom, left, right) and page numbers would help quite a bit. Print all fails miserably from function to function. Individualy printing each function does work better but takes great effort to get a readable result. That said the screen capture does give a better result quicker than many other plc/panel programs.
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