I_rock_well

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About I_rock_well

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  1. PLC control of Work Instructions

    Did you ever figure out a good method? 
  2. Trying to understand FIFO

    I am using a Controllogix CPU. Not at work so I can't double check, but I think it's a L73 running firmware 20.xx.
  3. Trying to understand FIFO

    I would like to store values in an array, in a way that makes sure that the newest data point is always in myArray[0], the second newest in myArray[1] and so forth. FFL seems to do the trick, but only until it is full. If I try to use FFU to unload it, I can not keep it to storing the newest value in myArray[0]. I tried resetting the control bit, moving and copying a zero, or a bool with value zero into the .dn and .em bits, but nothing seems to help. I am very grateful for any suggestions, this starting to get frustrating. I do not care what happens to the oldest data, and my goal is to display the data on an HMI.
  4. Trigger button using OSR doesn't work consistently

    So I moved the comparator to rung 4 and bypassed the analog input if the gripper is closed. I think this actually a feature, not a bug. However, I found out I have a safety issue that I personally think is more important than the 2 hand stuff being tamper proof. When the PLC loses power, and the gripper is closed, the valve loses power and the gripper opens. I assume there is nothing I can do with the PLC and need a different valve, right? If anything this project taught me the importance of a good salesperson who knows his stuff and identifies problems before the customer does :)
  5. Trigger button using OSR doesn't work consistently

    Thanks again for your help, I assume placing the comparator on rung 4 should do what I indented the plc to do.  Now to the question of what I intended to do is enough. This is for a senior design project, so it will eventually be used in industry. The sponsoring company will have safety people look over it, but frankly I don't know how professional they are. The problem with the current setup is that operators could jump the two inputs to circumvent the two hand control, and a dedicated safety relay would prevent that,  correct? My understanding is that a safety relay takes the two inputs from the buttons, has some internals that make sure that the output of that relay only triggers when both inputs energize (or deenergize I my case). Couldn't an operator just as easily wire the output of a single button switch to the input of the plc, bypassing the relay altogether?  Or would the relay be used after the plc, with plc outputs as inputs?    Another question, which I know is know might not be answerable due to legal reasons: is a dedicated safety relay neccesary for a non life threatening device? The only OSHA standard I found is for mechanical presses, which I don't think this falls under. It's a parallel gripper delivering 500 pounds force, with a stroke of ~3 inches.  I do not have a problem purchasing a relay, but I need to convince my partner who works for the company who sponsors our senior design who wants to show how economical he is by keeping everything cheap.    And I'm not discouraged, I spend 4 years doing heavy math by hand for stuff that could  be better done with software. My only programming class was c+, all this is new and self taught, I'm even a little proud of myself and find it very rewarding as I see results quickly. 
  6. Micrologix 1100 Analog input programming

    Thanks, for once something was easier than expected. :) One weird thing so: I'm using a mixrologix 1100 (1763-l16 awa) with 9 (or 10, don't remember) and two analog inputs. I:0/4 should definitely be digital, but that's where my analog signal us stored. I am using rslogix micro light, and I was only able to chose a generic mixrologix plc. I assume that is the reason? Will this cause problems when I or another person tries to modify the program with rslogix 500?
  7. Trigger button using OSR doesn't work consistently

    That seems to be a plausible explanation, I will check that out tomorrow. Bypassing would just be a examine if closed for the O:0/1 in parallel with the grt, right?  Opening the gripper with a low analog (=air pressure ) value should not be a safety concern.  The pressure drops everytime the gripper opens or closes. I am unsure how fast it recovers. I hope it is sort of slow, as the gripper seemed to "malfunction" more often when I waited a few seconds before reopening/reclosing it. I am unsure what you mean by quick deactivation. I am a senior ME student, I'm probably missing something and just stating something obvious: all I want is two press the two buttons simultaneously once to close, another time to open the gripper.  If this doesn't solve the problem, is was thinking that I try to implement a latch/unlatch sequence with two osr, would that be a possibility? Thanks for your help, in hope one day I can give something back up this awesome community. 
  8. I am working on my first project involving a PLC, and am trying to implement a trigger button. I attached the program I have created so far. Strangely, it works only about half of the time. Sometimes the output energizes/deenergizes (in my case a solenoid valve which opens/closes a gripper) for a split second, but than returns to the previous state, kind of as if the osr triggered twice in rapid succession. I am using Rslogix Micro with a Micrologix 1100 (1763-L16AWA) if that makes a difference. Any help is greatly appreciated.
  9. Micrologix 1100 Analog input programming

    Not sure if this against etiquette to jump into a thread that isn't mine, but i would be interested in the answer: how do I address the analog input? Which command do is I use in rs logix?  I need something along the lines of "give me a true value if the voltage on the input is more than 3 volts" Thanks in advance. 
  10. I apologize, I should have phrased the question better. I am using two push buttons which I guess open/close a button relay. This is the input for the plc. The button relays are rated for 240ac. My question is, were does the electricity come from for the circuit which is opened/closed by the button relays? do they just need to be wired to the ac com and input terminal from the plc, can I just take 120v from the bus tap directly, or do they need a 120vac power supply?            
  11. Thanks for your answer. I have a second question: I am using two push buttons with button relays. Do those take the voltage from the plc, or do they need to be connected to a power supply as well? If it comes from a power supply, this would need to be 120V, as the on state of the digital inputs is 79vac according to the manual, right?   This is for a senior design project btw, I will not do the installation myself, just need to make sure I have all the parts.
  12. Just a quick question from a total noob: I have the ladder logic setup to drive a solenoid valve that takes 24VDC. The PLC I have takes 120VAC as the input, the output specifications just say "Relay". Am I correct in thinking that I need some sort of 24DC power supply, or can I somehow set the output to supply 24VDC?   I hope I gave all necessary information, I am a mechanical engineering student and a little out of my comfort zone. Thanks in advance.