Hartman

Hi again! Thanks for all the replies, the situation at the moment has been resolved by ignoring the outputs from the plc. In other words we now control the 3 conveyors via a PID controller in our dcs which outputs three 4-20mA on seperate cards to drive the proportional valves. The plc still has the active outputs we just disconnected them and re-routed from our dcs. The result has been very satisfactory with throughput from our mill increased dramatically. i'm going on a siemens course to help with future problems!

Hey, thanks for the reply. We are using a fluke 744 process meter. And yes we believe it is wired correctly. We have tested each part extensively and whatever we put in at one end we get at the other. I should point out that the way it is at the moment (with the output range 6.2mA to 8.7mA) the conveyors all run,and have done for years, but setting the power plugs up with this range is quite difficult. The output from the plc does range perfectly via the scada user control screen 0-100%-just in the smaller range. All 3 conveyors recieve the smaller range from their respective channels. Is it possible to limit the output range of a 4-20mA signal from an analogue module from the program itself? The program is designed to control the speed range of all three conveyor feeds over 8 stages according to the absorbed power of the shredder (hammer mill), could it be stuck in one speed stage? Maybe someone could look at the program-i dont follow the siemens codes very well! Thanks

Hi mike, I dont really have an e-drawing i can give you but i can tell what we checked out so far. We obviously checked the cable and resisistances and they were fine-we also hooked up a process calibrator from the plc panel and injected the 4-20mA signal and at the other end (60m away at the power plug) we got the full range as required. We also tried a spare power plug wired direct at the plc terminations-still only the 6-9mA range. Also we have tried floating earths and grounding both ends but nothing seems to change the output range. I'm almost certain that the signal from the output card is just not powerful enough for some reason, maybe

Hi, I've recently come across a problem with one of our plc's its a siemens s7 300 and the problem comes from 2 analogue output cards (6ES7 332-5HD01-0AB0). These cards have 4 outputs each of which we use 3 channels on each. These 3 channels control 3 hydraulic motors (3 seperate conveyors) via proportional valves which are powered by vickers power plugs which are supposed to get there 4-20mA signals from the analogue output cards-problem is for some reason the output range from each channel for all six conveyors is 6.23-8.79mA? The first problem is i find it very difficult to interogate siemens programs as i'm new to this so i'm not sure if this range has been set in the program and where. Secondly to try and bypass the problem of the output range i bought an externally powered signal convertor (6-9mA input with 4-20mA output), which worked perfectly for one conveyor but drained the power from the other 2 active output channels rendering them useless. So can anyone tell me if at some point someone realised that the full 4-20mA signal from each channel was unobtainable for some reason and changed it to allow all 3 to operate all be it in a smaller range..and also why is the output voltage for 1 card 1.6v and the other 2.3v?

Good news people...I have got comms now!! Although..I'm not sure how...As you mentioned above ken, i checked the value in n100:4 and it was 14,and the others were as follows n100:2=10 n100:3=12 n100:5=16 and n100:6=18 The only way i could get the comms to work was by setting all the above values to 0 ? This is obviously not working correctly as the control room screen is only 75% correct, info such as pump on or off,motor on or off etc.. The integer values n7:0 to n7:7 are way off the mark(on the control screen) of what they should be even though the output values in the ladder are correct. I think its to do with the values in n100:2 to n100:6 but how do you know what these should be? needless to say i'm over the moon with the progress..Thanks to all who replied..

hi..happy new year folks , i have managed to use the programs suggested above to check the dcs messages,and this is what i've got.... Frame Analysis (<SOH><EOT><NUL><NUL><NUL><LF>p<CR>) -------------- Error #0007 The checksum is invalid. Actual=0x2ee70c Required=0x7ebf The frame has errors but there may be sufficient information to analyse the message. . We do not support analysis of of some functions in this version of the application. Function code=14(dec)=0xe No further analysis is possible. If someone can make sense of this i'd be very greatful.

Im not sure how i find this out i've been reading up on integers and words and i cant get my head round it..is there a way of seeing the values when i'm connected with RSlogix?

The saga continues...I didnt realise this before but having checked the N100 tables i'm getting the fault 104 at N100/21 which is bad length (exceeds data table length) and at N100/24 fault 3 which is illegal data value?? what does this mean exactly and what should it be??? The modbus driver is active and everything else looks ok..

I tried the new 232 to 422 convertor and alas the signal to the dcs stayed the same..which i suppose proves that the westermo was working ok. I have no idea what to do next! ... is there any literature that can help me with communications problems? i need something to talk me through a complete set up of the comms.. thanks

Thanks for the replies guys.. I do have the prosoft RTU 5/03 card which as you say does support modbus protocol, The comms did work for a week but after a power cut it never worked again..that was a long time ago and a few people have tried to repair it! The 1747 KE was there to connect to a local pc next to the plc which now also doesnt work.but i'm not worried about the pc.The comms to our control room are all i'm concentrating on at the minute. I have ordered another 232 to 422 convertor to see if its the westermo unit causing the upset.I also have a prosoft mcm-3150 module which i'm tempted to try and install but i dont think its going to solve the language barrier problem.. Thanks again..i'll keep you posted..

Just an update for anyone.. Ive checked what signals we are getting at our dcs and its coming up as illegal data value! but at least its getting something.Our dcs is the master and the 5/03 is the slave.I checked the dcs settings which were modbus protocol,8 data bits,1 stop bit,parity none and 9600 baud rate. I tried configuring channel 0 to match but i'm not sure of the protocol for modbus? should it be full duplex? also will the plc know its the slave? where can i check that setting? i'm close to getting it working...any advice?

Hi all..I'm new to the world of plc's but recently i've taken on a fault at work that has'nt been resolved for a couple of years Anyway the problem is communications between our dcs and an AB 5/03. Apparantly we did have comms for a short while coming from the processor (rs232 from modbus slave) going into a westermo ma-42 which presumably is a convertor to RS422 because the distance is about 100m from plc to dcs. On the rack there is also a 1747 ke module which was connected to pc using the df1 port-this also does not communicate (even with the link cable from dh485 from processor to 1747ke module). When a laptop is connected to the dh485 on the processor it connects fine. Anyway i know i probably havent given enough information here but if someone can help.. The cable connections themselves are ok and the westermo unit does actually flash rd and sd and i'm told that the dcs side is fine too.