Joa

I think you are right. I have to find out the right settings and processes by using the PC...by that I will enter new terrain again and I have to proceed step by step. May you have any recommodations regarding required test software(if possible freeware)? Today I got also an information from the customer support...It seems that I was on the wrong track. The drops occur only in the IO/ UAC RS4 struct(more related to RxTX commands like UDP or TCP) and they are not relevant in my case because I'm configured to the Modbus Protocol. In the global struct which relates to Modbus master communication there are no drops and everything is fine there. I've been told that this little problem will be fixed with the next upcomming version. Thank you all again for your time and your support! Joachim

Hi kratmel, I tested it ...it must be somezhing else.. Thank's for the idea

Hi, I made tests with different versions... In my project I have up to 25 periodic and 15 aperiodic commands only for one valve. But I made tests with only 3 registers to be read. The problem remains the same...even in the version with only with aperiodic commands I get drops after buffer is full. However the registers can be read anyway and the Integers can be transformed into Real anytime It's a good point you mentioned that 485 needs some time for buffer clearing...this is something I don't understand. How can I have influence in the timing to make sure that theres enough time between the commands?

Hi Ausman, I changed the slaves IDs to 4 & 5 as you proposed. Unfortunately without any progress..I still have drops after full buffer this is a tough one and slowly I'm running out of ideas Thank's a lot for your time

Hi Joe, now I tried with 9600 8N1 with only 1 valve, before it was running with 19200 with 2 valves... no positive effect:(, I still have drops after Com Rx buffer run full. I'm wondering if this might be the reason. ...buffer too small or missing reset??? What do you think, is this possible? P.S. I think Auto baud detection works only with Bacnet on this system. Thank's a lot for your support.

..further I have noticed that if 2 slaves are connected the Rx Signal looks not correct at the end of the chain compared to the signals with one slave ..however data drops occur in both cases. 2 slaves 1 slave

The 2 connected slaves different ID's attached the pdf of the slave valve.. I also tried some tests with modscan...-some responses have checksum error Novocon_data_sheet.pdf

Thank's a lot for your feedback. Joe, I guess the same. ..and I already made some measurements (see sketch) with termination dip "on" and "off" -It doesn't make any difference concerning Voltage levels. This is something I don't really understand. Next idea is to implement a termination box etc. with adjustable potential for the signals...(Honeywell RS-485-PCD7.T162) Kratmel, I had the same idea a couple of weeks ago so I wrote a program where com commands were processed sequently with a time delay of 500 ms in aperiodic manner just like the way shown at UniLogic_Examples\UniLogic Examples_V1.32 Rev 61\Communications\MODBUS RS485 I still have theses Rx drops after Com RX buffer is full. So it must be something else Oszi shows following... I'm not a modbus specialist...what do you think. Is it correct if TX signal looks different to RX? I'm looking forward to more inputs

Hi again, Meanwhile I checked the signals & voltage levels of the modbus connection and I have some doubts about it. It would be great to get your opinion.... The voltage level of the 2 wires in idle(No commands sent) are: U (/D) =1,75V D (D) =1,45V U (/D-D) =0,3V Spec. of 2 wired serial modbus describes: U (/D) = 2,8 V U (D) = 1,9 V U (/D-D) =0,9V ..also checked data transfer signal with oszi. Could this be the reason for my com problems? ..probably yes I guess

Hi Ausman, thank's a lot for taking time. I checked again, The dip switch of the last valve for the terminating resistor is set. What I do next is asking the supplier why signal cable is not drilled and shielded. It was included in the package..I would also like to measure the signal quality... Cheers Joachim

Hi, I'm having trouble with a Modbus RTU connection and unfortunately I don't have enough experience to understand the problem. In my project I would like to control 2 or more control valves that can be operated digitally and analogue. Communication with the first valve takes place via a USC-X10-RA28 expansion module (2-wire serial Modbus RTU interface), all other valves are connected with a daisy chain cable. When sending setpoints/operating modes I sometimes have to click the button twice and after a while the connection may hang (status 1). I noticed that the Com Rx buffer is running full to the value 4096 and then the Rx drop counter starts counting. I assume that the PLC can no longer buffer the received bytes and so the data is lost. Am I right and how could this problem be solved? Thank's & BR Joachim

Hi, I checked the ladder again and found a little mistake in the logic. ....now it works Thank's a lot for your help & comments

Thank's for the commend... I understand Status 4 means PID is running. ....but I don't understand why CV is 0 when PV differs to SetPoint

Hi Dave, thank's a lot for your response. sorry the screenshot confuses a little bit. The PV max value is multiplied by factor 100 in the ladder later...so it's actually 3000. In attached another screenshot with all values used by PID Config when Status is 4. (PID RUN) I'm not sure if all values are plausible because I don't have much experience with it.. Would be great to here from you again..

Hi all, I want to control a flow control valve using the PID function. After the autotune run is completed and the Status is 4, the CV control value goes to 0 instead of dynamically adjusting the value. May someone had the same problem when using an analog output? I would be very grateful for tips and advice.. BR, Joachim