FX2n Cannot connect to PLC

[novost 0]

Hi, Just got a brand new FX2n out of storage to program up as a spare for a machine overseas and can't get any communication through the programming port. I just get the "Cannot communicate with the PLC for one of the following reasons" generic message. It has been awhile since I've used the GX Developer 7 software so checked with another PLC (FX0s) and the software/cable/USB-serial converter all works fine. Then I thought I'd disconnect the battery for a while to see if there was something in program memory causing the issue. Reconnected the battery and powered up. Now the PROG-E light is flashing and power LED is on but still no whisper from the PLC...... Any suggestions would be most appreciated.

[kaare_t 155]

If the PROG-E is flashing it usually means there is a problem with the CPU or the PLC itself - a critical error! Did you put the PLC in STOP before powering up? It could be something is left in the program memory causing the LED to flash, so if it is in RUN mode when you power it up, maybe something is causing this issue. If that doesn't help my guess is that it's broken.

[novost 0]

Yes the PLC was in STOP mode. As I said PLC was new in box-no programming carried out previously. I don't like your guess that it is broken! When powered on the first time, the PROG-E light was off but no comms. The PROG-E light started flashing after I disconnected the battery to clear program memory. I have been working with these for 15 years; never seen this though. Any other ideas?

[kaare_t 155]

How long did you have the battery out for? By the way; the reason you cannot get comm now is because the PROG-E is flashing (as I said it indicates a critical fault).

[novost 0]

Battery was out for 30 minutes or so. This I have done before to clear program memory. Usually the PLC is ready to program after that. Is it perhaps a problem with the PLC booting? I don't know how the firmware is structured but I guess it must have a bootloader running to then load the ladder.

[kaare_t 155]

Yes, it does have pre-programmed (flashed) chips with varuous functions, however not really sure how it's all done since Mitsu won't get into details, but you cannot flash the firmware of a unit (maybe Mitsu can, but we cannot at all!). I'm heading out on a job, but you could also try booting the PLC without the battery. That is not a problem, there's even a bit in the PLC to disable the battery warning. I've used this several times in the shipping industry since they don't want to have batteries inside the PLCs (the use EEPROMs instead to hold the program). Try to boot the PLC without the battery and see what happens. Also, try to have the unit without the battery for more time (without the power supply connected) since there does exist some capacitors that may or may not hold current for a period of time. I know that 30mins should do it, but just to be sure I would go for a couple of hours without battery/PS.

[novost 0]

Thanks for your suggestions. I'll try them, see what happens and post back.

[Edwin 0]

i believe your communication port have some problem. The PROG-E is flashing due to you removed the battery and the internal program (even the empty program) already loss. I do not think the internal programming will cause the communicate of PC failure even with the error.

[novost 0]

Well I tested comms with battery out and after power off overnight and nothing had changed. No response from the PLC. I now think the PLC must have a faulty comm port and I should just send it in to Mitsubishi. Anyone have any other ideas?

[Cetronic 1]

What I can tell you is, that if you are using a standard comms port on a PC and the PC and PLC are connected to different Mains supply point you will almost certainly damage the Comms port on the PLC (ground loop induction) it has happened to me once during a moment of forgetfullness. I have no experience of this when using a USB convertor and not something I would intend to test. If I dont know the mains supply points I always run of Laptop battery.

[kaare_t 155]

One small question; did you select the correct port number in transfer setup (since you're using an USB<->RS232 converter)? Also; are you SURE that the USB converter works with your OS/PC? I recently upgraded to Win8, and needed to change out my converter since the driver wasn't compatible with Win8, however no error message or similar in the OS - it just stopped working together with the PLC... @Cetronic: You are partially correct. Did you connect the shield wiring on the SC-09 when this occured?? Remember that what you're talking about is the different potential between two separate power systems, and as long as your computer runs on a battery you still have different potential than the PLC running on an external source... However I do agree partially with your since the potential may be greater when using two 110/230V sources than when using your 10-20VDC battery supply in your computer, but still - shouldn't be an issue. However I NEVER connect the shield wire on the SC-09.... My quess is that there was something wrong with the chassis grounding in one of the sources when you destroyed the comms port. Normally this is not an issue (I've done it many times, you too probably in the past without problems).

[Cetronic 1]

Thanks kaare_t the cable I was using at the time was an SC-03 as I remember (Number of years ago) Using SC-09 now and NEVER connect the shield wire. My reason for the comment was that PROG-E was the exact error with an FX1N and Mits Aust wanted about the price of a new unit for repair.

[novost 0]

Thanks guys for looking in on my thread! Just want to emphasize that the laptop/software/cable /USB adapter/mains supplies, EVERYTHING is OK. The FX2n-48MR-ES/UL was new out of the box, wrapper intact and it is pretty unlikely that I fried it or I would have fried the FX0s I have just used so to check everything. So, I may have had a defective unit which Mitsubishi insists never happens. Ho ho. What is intriguing I think is that it initially had no error light lit, just power green but no comms. After disconnecting the battery, the PROG-E started flashing. This is probably normal since it now does not even have a blank program it it. From this state given working comms, should one be able to program it?

[Edwin 0]

FX2N PLC already stop production since Sep 2012. Would you bought a second hand PLC? Strongly recommend you to use FX3U PLC.

[kaare_t 155]

I do agree with Edwin, I would recommend you to just get a FX3U unit, why use the old FX2N as a replacement. However, I hate it when not finding the root cause of a faulty unit which sould indeed be functional. I do partially agree with Mitsu, it seems very strange that the unit is non-functional. Have you tried removing the battery and power for at least 24 hours? I still suspect that something is left in the unit that aren't cleared caused by a capacitor or similar...

[napster 0]

you said that you got your plc "out of storage"?you mean it is a spare?how long does your PLC in storage? the prog-e occured because you removed the battery(for over 30mins?) try clearing/formatting the plc memory.(cycle on-off after) then try to read again.