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About ControlsGirl

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  1. Emergency Stop Circuit Scenario

    Well, I feel like there are a few types of responses to this. I cannot say that I am "all knowing" about safety. I also have no experience with MCCs. However, I will say that safety circuits need to be discussed more and that we, as a community, REALLY need to start discussing safety circuits that are completely digitalized. I think your question is great and very relevant.   From the experience that I do have, this is what I can say. One of the responses that you might get will mention a risk assessment. Maybe you can get lucky and a machine risk assessment that will tell you that a safety circuit with redundancy and pulse tests, etc is not required. If that is the case then I do not see why you wouldn't be able to just use the PLC. Another way of looking at it is to check if it possible to replace the PLC with a safety rated version of it. This might solve your problem.   I just did a quick google search and Siemens mentions safely controlling motors through their MCC. I'm not sure if the PROFIsafe layer can run on a Modbus protocol but if it can, you might already have what you need.
  2. PLC's, servo, and VFD OTHER than AB

    @LURBY, I have a few comments. First, I know that part of Rockwell product prices are set by the quantity of items you purchase per family. I worked at a place once that had contracted out the panel build and had the panel shop purchase all of the material. I wanted to change that and purchase products ourself once we got a huge 3 million dollar line. I had a 100k worth of Rockwell products in it. Because we didn't have a history, our distributor did what they could to discount couldn't do much. Part of what they did was transfer over the discount from one product family that we did have to another product family.  (I think they chopped off about 12%). However, they brought in a Rockwell Sales Engineer who was able to work with the distributor which resulted in another 20% discount!! My favorite PLC developement software, by far, is Logix5000. I would stop buying the micros and look at the low end Compacts. The prices almost overlap and using tag based programming and updated software with MANY conveniences truly makes life so much easier and enables author's to write code or change code to be much more portable, etc.  With all of that being said. if you want a cheaper PLC, I've used the Unitronix PLC/HMI and I really liked it. There were a couple of quirks in the software that I ran into but the tech support was readily available, very easy to get a hold of, and super helpful. I've worked extensively with ControlLogix/GuardLogix, CompactLogix, S7-300s, Modicon 984s and Quantums, and then the Unitronix.   As for servos, I have not worked with Rockwell Servos but I've worked pretty extensively with Siemens, Unico, and Emerson. The Emerson servos that can be used with the Emerson PowerTools Pro software are my favorite(digitax ST/Unidrive). The software is extremely intuitive.  Hope this helps a little!  
  3. CAD Software for Schematics

    Whatever is free/cheap isn't going to be friendly. For one project, I would use draftsight and cross my fingers that I have a VERY good reference. If its for a lot of projects. I would cough up the 5500 and buy Autocad Electrical. ePlan is around 12k.
  4. How do you mount exterior tags or plaques?

    What size do you usually use for something like a 1.5"x0.5" lamacoid tag?
  5. Simple PLC Coding Question - RS Logix 5000

    The only way to edit code in one place and have it update in other instances is to create an AOI and use the same tags. I will say that it seems amateur to write the same piece of code twice just to view. You could bookmark that rung or create a watch table to monitor the values.
  6. LBL JMP

    Hey Guru, I originally typed this out but my loop is working I just didn't understand that I prob wouldnt see the Index move because I think it only updates it at the end of each scan...and Index is always going to be 3 at the end of each scan. Am I right!?!? Judging from the lights on the HMI, I am I'm trying to jump back just to loop through a piece of code. I can not get it to work. First I couldn't get it to count. Now it counted but the value I was using to index is stuck at it's high point. I am moving a 1 into that index tag before my lbl instruction so the next time it scans through, it should write a one in there. Could you show me just a snippet of a loop you have that is working? Also, mind sharing the excel secret??? mov(1->Index) LBL...code code code Add(1 to Index->Index) LEQ(Index, 3) JMP
  7. HMI (Panel) & PLC Logic

    Ever since I have started, it always is best for the customer to keep as much logic on the plc as possible. This goes for any perephrial device. Robots, screw guns, etc. It is much more convenient to only have to look in one place and only have to train maintenance to know how to use one piece of software.
  8. Has anyone seen, used, or designed a FTView ME application where there is only one display used for multiple groups of manual motions? If so, care to share what the design techniques were? I've done this before by having the station button update the name of a UDT with parameter files. It worked very nicely for that application. However, I am taking an HMI application that has already been designed for a line and I'm trying to make it much less cumbersome to update. I'm interested in hearing the ways other people have come up with in hopes that it might lead me to a very good solution for this project.
  9. Developing Allen Bradley AOIs (Add on Instructions)

    Did you learn how to program in a scripting language like C before ladder. I am just now getting into writing AOIs and I instinctively want to use them like a call to a function in C. I only execute it when I need to. However, I just spoke with some older controls engineers at my work and they say they like having it always enabled with some kind of bit that passes that initiates some function within. I guess that is where ladder is different. You can stop the process of an AOI be disabling it, even in mid cycle. In normal scripting, it executes to complete before jumping back into the rest of the code. I just had an "Aha!" moment
  10. Panelview plus not talking to Emulator PLC

    I followed this and unfortunately it's not working. Once I added the link under the Enterprise link under the EtherNet section, I added the backplane. I expanded that and it found my emulator. The PLC is in slot 5 (This is the way it was set up on the actual line). I'm not getting a communication error on the HMI but its obviously not connected. I'm using a PV+1250 V6.10.
  11. Error proofing system needed

    This RFQ is nicely detailed. However, are there any specific device brands and/or other plant specs for the construction?
  12. New PLC student questions?

    I'm 25 and in my 3rd year of my career. If you look on the east side of Michigan, there are TONS of offers for Controls Engineers with almost any kind of experience. Experience is key though. Luckily with my degree, I had to spend three semesters working with a group of controls engineers, monitored by my school. That experience got me a good little gig making 20 bucks an hour. I've moved up quite a bit since ;) There's been a drought of Controls Engineers and industries are beginning to build again. From my experience, you are definitely going in the right direction. There will be small mom and pop type shops that'll be willing to hire you if they have someone experienced enough to guide you. Also, I hope you like to travel.
  13. Shielded cable - Ground both ends?

    Sparky, I really liked your response.
  14. Safety: EN 954-1 Category 4 and PLC Wiring

    Panic mode, Could you post a reference to a document or something that states what is required for certain safety category levels. I'm in a debate with a co-worker and he said that whether or not a safety circuit has an automatic restart and/or whether or not it is self-monitored is not apart of what is considered for safety category ratings. I was taught differently. Now I am trying to dig up some kind of documentation to support this.
  15. General PLC selection Help!

    Hey everyone I am very new to the use of PLCs and was performing a simple solar experiment for one of my courses and am kind of lost. My experiment is to take a solar photovoltaic panel, (simple cheap panel) and connect it to a PLC to control a valve opening or closing output. It sounds simple, but I am unsure of the inputs (solar being a DC input? would it be Watts or Voltage or Amperage?) also the outputs and where to start even with what to purchase. I am surprised that they are not having you design this using only hardware or by using a little microcontroller. One big question that I have for you is if you expect the solar panel to either be off or on or if you expect the output of its voltage or current to vary. Do you turn on the valve when you get an "on" signal from the panel? or do you watch the output value sway up and down and only turn on the valve when the panel's output is within a certain range or hits a certain point (other than fully on)? Here is what you need to figure out. You need to look up the data sheet on the solar panel that you have. Look to see what it's output characteristics are. I, personally, am not familiar with them but I'm assuming that the output of the circuit will remain close to 0VDC until the voltage reaches some nominal value (ie 24VDC). If so, than this would be considered a digital input. The vast majority of PLC digital input options detect 24VDC. The standard digital input cards in America are 24VDC and 120VAC. Sinking or sourcing? The standard American practice is to always use sourcing inputs which would mean that you will need a sinking input card. I believe that most cards have the option to be either or. I would think that your panel would be a sourcing input because when it activates, it will provide the power (created by transforming energy to the sun). The other possible scenerio is that the voltage or current will range between something like 0-10VDC or 0-20mA. If so, you will need an analog input. For the output, it depends on the solenoid of the valve. If you are choosing the valve, the standard options (in my industry) are 24VDC and 120VAC. Pick the output card to match the voltage required to activate the valve solenoid. The standard in my industry is to use sourcing outputs. What class is this for?