Does a PLC hold instructions? HELP please!

Ok, my parents own a dry cleaner and the main machine broke. THey said we need to replace the main PLC, which is a Mitsubishi Melsec FX2N-64MR.

THe machine has an LCD keypad in the front, which lets you control some options. We were wondering if the machine program resides on the PLC itself, or if it is somewhere around the keypad. THanks

The program is in the PLC itself.

However, replacing the PLC might be the method the dry cleaning equipment manufacturer uses because he knows his customers will not have the skills ncessary to repair the equipment. It could turn out to be something very simple.

It may be worth your time to find someone in the area who repairs PLCs. There are probably hundreds relatively close by to you on Long Island.

Alaric said:

The program is in the PLC itself.

However, replacing the PLC might be the method the dry cleaning equipment manufacturer uses because he knows his customers will not have the skills ncessary to repair the equipment. It could turn out to be something very simple.

It may be worth your time to find someone in the area who repairs PLCs. There are probably hundreds relatively close by to you on Long Island.

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Exactly, and even if it is the PLC you'll need someone to enter the program (if its accessible or available).

1)SO does that mean replacing the unit with a new one will NOT resolve the problem? IT seems as though the PLC will be blank and the machine program will not be run?

2) Is the Mitsubishi FX2N-64MR even a PLC?

THanks

THey said we need to replace the main PLC

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first of all, who is “they”? ... if it’s the machine manufacturer, then you’re probably going to have to get a new PLC from “them” and install it ...



here’s the basic idea: a PLC is an “industrial computer” ... a PLC doesn’t have a keyboard for an input device ... instead we wire up buttons and sensors to serve as inputs ... a PLC doesn’t have a screen for an output device ... instead we wire up valves, motors, etc. to serve as outputs ... (your LCD screen is sort of an exception to this basic rule) ...



now then ... just as a computer is useless without software (enter Bill Gates), a PLC is also useless unless someone has written and entered a program into its memory ...



now the machine manufacturer undoubtedly wrote the program to match your PLC and your machinery ... they downloaded a copy into the PLC ... if the PLC has “crashed” then it MIGHT have lost its program ... then again, the program MIGHT still be intact ... MAYBE all that the system needs is a wire from a sensor reconnected ... MAYBE a switch has gone bad ... we can’t tell from here ... but we can try to help if you can give us the information that we need ... but this could take some time ... especially if you’re not familiar with PLCs in the first place ...



my advice is to contact the machine builder and do whatever they tell you to do ... if this thing is how your parents earn a living, then just getting it fixed as soon as possible might be the best course of action ...

SO does that mean replacing the unit with a new one will NOT resolve the problem?

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if you just buy a new PLC “off-the-shelf” and plug it in then you will NOT solve your problem ... UNLESS the new PLC comes from the machinery manufacturer AND has the correct program already in place ...



I hope that this helps ...

"They" refers to the manufacturer. It costs more from the manufacturor to by the PLC, so we were going to by it off the shelf(which is cheaper).

What the previous poster noted was that the program is in the PLC, which means we are forced to get it from the manufacturer. We were trying to make sure if this is the only option.

THe keypad has a serial port connected to the PLC. we were trying to determine if the program doesn't reside somewhere in the keypad components.

I think you are ultimately going the more expensive route.

Will the machinery manufacturer send you the plc pre-programmed? If not then by all means get the plc from the cheapest source. If the manufacturer will send you a pre-programmed plc, however, go that route. By the time you either buy the required programming software or find and pay someone to download it for you, you will most likey eat up the price difference.

It is very unlikely that the display you refer to contains the program. Some plcs support a removable memory device but that is probably your only shot to get off ohn the cheap.

Keith

From what you've said here your best bet is to buy the PLC pre-programed from the OEM; if you can pay them to come out and install it I'd recommend that as well (then they're on-site where they can help you quickly if the PLC isn't the only problem).

Can you tell if the PLC has an EPROM like one of these?

http://www.mind.ne.jp/melsec-f/english/plc_fx/lineup/accessories/index_e.htm#DM

If it does have an EPROM the program may be contained on the EPROM that you could remove the EPROM and put on a new black PLC. There are a couple plcs of the model you described on Ebay. http://cgi.ebay.com/Mitsubishi-Melsec-FX-64-MR-PLC_W0QQitemZ7607630119QQcategoryZ97184QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I am not saying this is the best route for you to take, but just laying out some different options. I have not worked with any Mitsubishi plc's so don't take this as any expert advice. This option would probably be the lowest cost, but with the most risk of losing time getting the machine going again.

Does the existing PLC show any fault indicator lights? Does it show any lights at all? Does it smell like the magic smoke has been let out?