Colin Carpenter

The high speed counters are "hardware" linked to various specific inputs, and you need to know which counters are linked to which inputs. You can download the FX2N programming manual at this address: http://194.130.244.64/branch/database/serv...amp;portal_id=1 You can check the type of encoder in the following way: I assume that two of the three wires are for 24VDC+ and 0VDC. These will power up the encoder. (If it takes other voltages (eg 12 VDC) then you would have to interface through a solid state relay as the PLC cannot "see" anything below about 18VDC.) The third wire is the "switch wire" and will EITHER connect 24 V+ ONTO the PLC input and SINK current into the input(in which case it's PNP) and the input will light, OR it will connect 24 V+ AT the input and will connect it to the 0V, in which case it will SOURCE current from the input (in which case it's NPN) and the input will light. Personally, I hate NPN systems, as they seem counter intuitive to me. The other point is that you can't have a mix of PNP and NPN sensors on one PLC (without adding other hardware), they have to be all one type or another.

I doubt if it's too fast - from the manual: For FX2N & FX2NC Inputs X0 and X1 are equipped with special hardware that allows higher speed counting as follows:- Single phase or bi-directional counting (depending on unit) with C235, C236 or C246; up to 60 kHz.- Two phase counting with C251; up to 30 kHz. 30,000 pulses per second is pretty quick. Just a few simple things to look for: a) There should not be mention of X0 in the programme, just something like: LD M100 OUT C235 K 100000 would do it, where M100 is the (for no reason) bit that enables the counting to happen. (Note that it is different to a normal counter.) b) Is your encoder a PNP or NPN encoder? c) Have you got the S/S terminal linked out? Link it to 0V for PNP or 24V+ for NPN. Leaving it not connected is not an option, as the strangest things can happen.

>>I don't have a high speed counter in the system. Would I need one for these kind of speeds?<< Depends on the cycle scan time of the PLC. General rule is that if the pulse duration is shorter than the scan time, then there will be times when a pulse "happens" during the scan time between refreshes, and the pulse will be missed. If you are looking to count 1500 pulses per minute, then this equates to 40 ms per pulse, but, the pulses have to go on and off in that time, so assuming the on and off times are equal, then, as long as your scan time is less than 20 ms, you should be OK. It is possible with IEC Developer to interrogate the PLC for its current max and min scan times, (and presumably also with GX Developer) In the past, if I've had to do high speed counting for several inputs and I'm concerned about the main PLC's ability to see all the pulses, I've often installed a small FX (cheap as chips on E-Bay) and used the multiple high speed counter options on the FX to count the pulses, then give a slower, longer pulse to the main PLC every time (say) 10 pulses has been counted. The FX range is really good at this. Regarding working out the speed, the longer you let the PLC analyse the pulses, the more accurate it will become. For example, if you're counting something that is generally giving 10 pulses per second, but sometimes 9 and sometimes 11, then the scaled up value (per minute) will be 540, 600 or 660, which is a big difference. However, if you write some simple code to count the pulses for 1 minute, then display that value, then the inaccuracy is only 1 part in 600, in other words, very accurate. Just experiment with moving counter values to data registers, resetting the counters and doing a bit of subtraction.

Do you have to do it with a PID controller. I've used the PID function in the FX2N many times, but always with an analogue control valve to precisely adjust the amount of steam or the amount of flow. I've never used a PID block with a digital output, and I'm not sure how you would do it. How you would convert an analogue MV value into digital switching would require some thought, or maybe some more hardware. Could you not just programme it as a simple thermostat. ..... when temp less than low setpoint, turn on heater, when greater than high setpoint, turn off heater?

Do you know the difference between Global Variables and Local Variables? Your screen shot is of the header of your POU, and the variables shown are "Local Variables". To assign a Mitsubishi address to a variable, it has to be done in the Global Variables section.

Why use structured text? If the manual doesn't exist, you can be pretty sure that almost no one uses it. Which means that you'll be the only person who can understand it....... which can lead to a lot of problems. IEC is very good at graphical ladder ..... why would you not use it?

M8000 is the "always on during run" bit for any of the FX range of PLCs. For example, if you wanted a light to be on when the PLC was in run mode, and you have connected that light to output Y0, then LD M8000 OUT Y0 would do it.

Hello Mate, What I still don't understand, though, is that all of the digital input modules give a "% value at a certain voltage", depending on the voltage that the inputs are designed to work at, say 60% at 26.5 VDC. Presumably this must relate to a fixed temperature point of the module? For example, at 55C, only 60% of the inputs should be on, or it will cause the module to "go critical". Presumably, at, say, 10C, overheating's not a problem and you can have them all on? Wonder what temperature the spec refers to?

They are all installed in panels in UK summer time conditions, which can get pretty warm .... maximum temperature would be 35-40 Centigrade, I would think. I have no idea what that bit means (and I also found it in the manual), certainly it implies that you can only have a certain number of inputs ON on a card at any one time, which seems pretty worrying if true, in fact it would make the PLC programme very insecure as it means you could never rely on the inputs. I'm sure it must mean something else, but I'm not sure what. All I can say is that I have NEVER had a problem with these cards not showing an input when it should have been doing so.

Not Mitsubishi, I know, but does anyone have any experience with hardware dongles and XP. I was asked to move a SCADA system (Wizcon v7.6) from a Windows NT4 PC to a Windows XP Pro PC. All installs OK and seems to run fine in demo mode, but it can't see the hardware dongle in the parallel port, so refuses to run in "full" mode. The PC has a "proper" parallel port and I've tried it in all the modes (ECP, EPP, bi-directional) but no joy.

Well, apparently it's a HASP driver, and they don't support it under XP Pro and they want lots of money to upgrade it and now I'm fed up .....

I've done lots of jobs with QnA and A1SX81 modules. They work fine. I have no idea what that statement means.

I only found out about Medoc V2.4 (the 32 bit version) recently, but I wish I'd known about it a few years ago. It would have saved so much aggro with me having to install Virtual PC so that I could end up with a true DOS environment to run the older V2.3 in. I believe it was produced by Beijers, not Mitsubishi, but seems to run faultlessly. It really is very good and runs very well in XP.

Thanks for the info. I'll definitely try the sentinel drivers and see if that makes a difference. I have contacted Wizcon direct, but, of course, they want to sell me thousands of pounds worth of updated software, which is not exactly what the customer expected when he just wanted the PC changed. They may yet come through with an updated driver, but I somehow doubt it.

If you go to the link shown below, there is virtually every Mitsubishi manual there. All the analogue modules are there and most have programme examples. Look for part numbers that include the letters AD (analogue to digital) or DA (digital to analogue) http://194.130.244.64/branch/database/serv...amp;portal_id=1

This one is pretty good - called a beginners manual. Beginners.pdf

Ah, but the game lasts pretty much a whole day, or, if it's a Test Match, then it lasts for 5 days. Each team has 50 overs (an over consisting of 6 balls), so assuming that their innings lasts the whole 50 overs, that's at least 300 balls that they can score runs from. If the bowler bowls a "no ball" or a "wide", then 1 run is credited to the batting side and another ball has to be bowled, so it's possible to have more than 300 balls in an innings, depending on how well the bowlers are bowling. Having said that, scores in excess of 300 are generally considered to be very good scores and any team chasing and achieving that score is reckoned to be doing very well. It's amazing how often these games go down to the last ball / last wicket, considering that we're talking about 1 run in 700 scored during the day. Must admit it's good to see the Aussies being beaten after the thrashing they gave us in the Ashes series this winter

Thanks, I'm always a little dubious about these schemes that come into being, flare briefly, then fade away into nothing. It would be good if it worked, but it would need Mitsubishi UK to keep things up to date.

Well, I've spent most of my life programming Milk Processing Plants, but I haven't a clue what the question means. It could be one of those questions that was written back in the '80s and has never been updated, and refers to the single line editing screens, the graphic editors and the tape based storage systems of those days (shudder), or it could be an up to date question that refers to the various levels of software sophistication in the various packages that exist today. Without knowing a bit more, it's not an easy question to answer.

I admit it is there if you look for it .... I was looking for a more obvious "tab" on the Web Site. But there are other worrying things about the list which makes me think it's not an active one. Last time I looked (several years ago), there was one company on the list that I noticed because I knew them. They are still there, but they don't actually have any MCE engineers, only two that are working towards it. Strange. Also, the entries for LC Automation are a bit odd, with Chippenham having a silver rating and head office having a blue rating. Now, in my opinion LC Automation are an EXCELLENT company, and they have helped me out of more sticky situations than I care to remember, but, at the moment, I don't think they have any real tech support at Chippenham, but they do have 3 or 4 top notch people at head office. I stand to be corrected on this one, and if someone from Mitsubishi UK could confirm that the MCE list is still active and promoted by Mitsubishi from their own web sites, then I might well sign up for the exams, especially as they seem pretty cheap at £70 per exam ..... which almost seems too cheap. Footnote (after typing the above) In fact, I was right, I've just noticed just below the link to the MCE is a small note saying last updated 05/04/04 - so no new MCEs for almost 3 years then!! Doesn't seem like an active, vibrant scheme to me.

I know Mitsubishi UK used to do something like that, in fact, they used to show the certified engineers on their UK web site, but I can't find it now, so maybe they've taken it off? Strange thing was that I knew a really good company that couldn't get the certification and a really duff company that did get it. Seems like there was a little more involved than just a degree of competence ... more to do with economics, orders and sales..... if you believe the really good company's view of things, though, of course, that could just be sour grapes. If the "CAT" still visits the forum, he'd definitely know more about it having been closer to the action than me. In fact, the Web Site posted by Crossbow seems to have taken the place of the section that used to be on the main Mitsubishi site, but it seems a fair bit lacking to me. I would have expected to have been able go to the site to actually find out a list of who was certified in the UK, but I couldn't find it. I wouldn't mind betting that the site hasn't been updated for quite a while.

Just bought myself a cheap FX2N on E Bay to use as a development / test bench / demo PLC. Was a little upset to find out that it only had 4K steps of memory, as I'd never realised that they did FX2N PLCs without 8k steps of memory, Oh well, it was cheap ...... Hang on a minute .... wonder if there's an EEPROM in it .... had a look, took it out .... back to 8K steps of memory. Result!!

Five or six years ago, I installed a PC running Windows NT with a SCADA system that currently "talks" to three separate serial ports, each one of which talks to a RS232/RS485 converter which then "talk" to a Mitsubishi, a Field, and a Modbus multidrop loop. The company want to upgrade the PC to a newer Windows XP machine, but the PC hardware only allows for half height PCI cards, and, in common with most modern PCs, it doesn't even have one serial port available. I know that there are "good and bad" com port solutions out there, so could anyone please tell me if they have had good experiences with a solution to add three serial ports to one modern PC. I assume that USB is the easiest way, but also know that some work and some don't. Thanks.

Thanks, those Digiboard options look pretty good, though pretty expensive. I remember the days when a 1 MB of ram cost £25 and serial cards were £5, now 256MB of ram costs £17, and serial cards are about £300. Times change.

What do you actually mean by that, has the PLC stopped recognising that it has 62 outputs? If you uploaded the programme from the PLC in GX Developer, you would probably only see lines of code, with no names or comments. As long as you edited the code correctly, then downloaded the code into the PLC again, then it "should" work. I'm just a bit worried that there are some parameter issues here ... any chance of posting or E-Mailing the IEC project, then we can have a look at it?