gravitar

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  1. Help me out with this, guys.. I'm familiar with the concept of set/reset coils. It's the same as latch/unlatch in an A-B PLC, it seems. But this whole "M" coil thing.. give me an example that I can grasp of what this would be used for! Especially SM/RM coils.. What is the benefit of adding retentiveness to a set output? This program I'm dealing with is full of SM/SR's.

  2. Does the "+" coil/contact signify more than just allowing a rung to be longer than the width of the display? I had plenty of room on the displayed rung to insert a contact between the timer block and the done bit, but it seemed that proficy would not accept that as a valid sequence of instructions.

  3. Hello! I'm currently working on my first experience with a GE PLC. It is a small automated shear table with a Series 90-30 CPU374 PLC. The program is already written, I'm just trying to make a few small improvements. Here's the first thing I'm trying to figure out.. I hoped that I could put a contact between a timer and its output coil, but Proficy didn't like that. So I'm figuring that I need to add a rung, assign a new bit to the timer done bit, and use this new bit with the condition I want to trigger the bit that's currently the timer done bit. Here's my problem.. I'm looking in the %M table, and it shows me a table of bits from 0-4096. I can see their present state, but I can't figure out how to see a "usage" table. How do I figure out which bits are unused in the program so that I can use one of them?

  4. If reliability is the main consideration, you're right to consider a PLC over a PC-based solution. Here's something else to consider.. Will you be able to program this with your employer's software, or will you have to buy your own? PLC software varies in price from several hundred to several thousand dollars. If you're only planning on making one (or a few) of these devices, you're probably going to want to limit your choices to the PLC families that use the least expensive software, or better yet ones that can be programmed with software you already have access to.

  5. I feel compelled to comment because I'm a toughbook user.. no, make that a toughbook enthusiast. First of all, Panasonic has several product lines that all share the "Toughbook" name. Personally I think that's a bad strategy. The only ones that deserve to be called Toughbooks are their "fully rugged" line.. The CF25, CF27, CF28, CF29, and the current model, the CF30. All the other ones probably have some degree of ruggedness, but probably not what would you would expect. I only deal with the fully rugged ones and have no desire to try any of the others. Ok with that said, everything Paulengr has said is true about the "fully rugged" line. They're comparitively slow, heavy, expensive, and the screens are lousy. If those are your performance metrics, then don't buy a toughbook. They aren't for everyone.. Heck I would go so far as to say that they aren't for ANYONE, other than those very few people that put reliability, impact resistance, weather resistance, and the couple of other features that toughbooks have (touchscreen, backlit keyboard, vehicle mounting, etc) above all else. I'm in that tiny minority. I think they're ideal for field service applications, or anywhere else that you REALLY, REALLY need that slow CPU and lousy screen to keep working, no matter what.

  6. I just got an auction listing for a company that was using "Anthropomorphic" welding robots. I wasn't familiar with that term so I googled it, and I guess it means "possessing human qualities".. Which doesn't really tell me anything :) Applied to the context of robotics, what does this indicate? Just catchy advertising jargon written by someone that doesn't know robotics?

  7. I just spent a good long while this morning trying to do just that. I might be approaching this from the wrong mindset, but I just didn't see how you could walk up to an "unknown" processor and capture the program! Anyone know how to do this? I'm using Cimplicity Machine Edition v. 5.0. Just to add insult to injury, the online help system in this particular installation doesn't work, either. It seems to want to go to the web to find the help files, but I'm having no luck getting it to penetrate the company's firewall, nor can I seem to be able to reconfigure it to use local help files.

  8. I see some here and some in the GE forum. I think that if you add it, they will come :) I wonder if there has been enough of an increase in active membership here that it might work now even though it failed in the past?

  9. You know.. the potential is there for me to learn a lot.. but I must confess, I'm on my fourth week in this place and I'm still not really sure what I supposed to be doing. So far I've just been watching from the sidelines, doing clerical/office work, calling vendors, writing memos, etc.. they keep on telling me about this job and that job that needs to be done.. Great, I think.. I'll actually get to wire something up or make a change in a program, and be able to show that I'm actually good for something. My boss keeps on telling me that "my time is much too valuable" to do an electrician's job, and they'll just hire a contractor to do that. AARRGGH!! I hate to come right out and tell the guy "BUT I'M NOT DOING ANYTHING!" but the fact of the matter is, I'm not making very good use of my time or the money they're paying me to be there. Probably the only things I've done that are worthy of a controls guy are to argue with maintenance about the safety features they aren't implementing, and argue with another controls guy about how a simple, passive sensor manifold is NOT a remote I/O block :) The project manager asked if we could do something and he had the nerve/stupidity to tell him we couldn't because "those fixtures were wired up with a special Remote I/O to DeviceNet adapter.." Give me a break dude, if you're going to lie to the guy, at least make it believable! But anyway, I'm quickly gaining the reputation as the new guy that likes to make trouble for everyone,so I'm wondering if I should just start keeping my mouth shut and collecting my paycheck..

  10. In fact, it isn't even accurate to call that an ethernet port. It does use an RJ45 connector just like the ones that are used for ethernet, but the RJ45 connector has been used for many, many different things over the years. 10/100BaseT ethernet and DH485 are just a couple of them. I don't think I would go so far as to say that anything would be damaged by plugging an ethernet cable into the DH485 port (believe me.. lots of people have tried it!) but you sure wouldn't be able to communicate.

  11. Thank you for all the insight you've all provided. I agree, it'll be a good learning experience if nothing else. Hopefully I'll at least be able to figure out what hole to plug the programming cable into on all these different PLCs! (Who would've figured that you program a GE PLC through an unmarked hidden compartment on the power supply.. I felt pretty foolish a couple weeks ago when I figured this one out!) Anyway, in my opinion, it's true, "Ladder Logic is Ladder Logic", regardless of brand. But I suppose you could say that about the languages we speak and write tooc, couldn't you? English.. Spanish.. French.. German.. They all use nearly all the same symbols. They all branched from the same origin. They're all used to accomplish the exact same tasks. So it should be a trivial matter to master them all, shouldn't it? But wait.. what about all the regional/national customs that you would have to master too? Well I'm running into that too. Like I said, I wouldn't expect to "program" the power supply. I didn't realize that when you're online, you have to sit and wait for the ladder to "update" before you REALLY know what's turned on and what's not, and sometimes you have to wait a LONG time (even though it's on ethernet.. go figure). I wouldn't have guessed that, even though the HMI and PLC are programmed withy the same software package, you can't do both at the same time. I think Ron hit it on the head when he said that the decision-makers probably don't even think about the PLC. They see a machine, a machine makes parts, and that's that. I'll try to get a handle on what's installed where and what software is needed for it, as a first step. Whether or not I'll have any luck making anyone consider that there's another way, is anyone's guess!

  12. I've got a question for those of you that are well-versed with US electrical regulations. The place I work for set up a piece of equipment as a standalone workcell, that was removed from a larger system. There are three electrical panels for controls, as well as a couple robot controllers and another small enclosure that is attached to a packaged piece of machinery. My question is about the three control panels. None of them have any sort of disconnecting means on the outside, but have manual rotary switches in them. Two of them are fed by a bussdrop cable that goes overhead and drops down about 100' away at a load center near another piece of machinery. The third panel is fed from one of the two mains-fed panels. So here's my question.. Is there any requirement about how close the disconnect switch must be to the supplied panels(s)? Does the voltage of the circuit affect this? One of them may only be 120VAC, but I'm sure the other one is 460 3ph. Is it acceptable for there to just be a placard showing a map of the floor that says "Lock it out over THERE"?