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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Ladder programs for PLCs
I want/need to replace a few relay-logic controls with PLCs. Typically, a
machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I should look? A lot of my stuff is old and doesn't have schematics yet alone a flow chart. The guy I had that was very good at this retired and moved to SC. |
#2
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Ladder programs for PLCs
PLCs only make sense when you have sequential events that are dependent on previous events, like motion fault detection. From what
I have gleaned from previous postings is that your equipment is mechanically timed. In my humble opinion I would concentrate on using electronic trigger technology, solid state relays and motion validation logic (feedback). The value of doing this is first reliability and secondly immediate system fault identification. You should be able to use a common family of components for all your solutions. Steve "Buerste" wrote in message ... I want/need to replace a few relay-logic controls with PLCs. Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I should look? A lot of my stuff is old and doesn't have schematics yet alone a flow chart. The guy I had that was very good at this retired and moved to SC. |
#3
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Ladder programs for PLCs
"Steve Lusardi" wrote in message ... PLCs only make sense when you have sequential events that are dependent on previous events, like motion fault detection. From what I have gleaned from previous postings is that your equipment is mechanically timed. In my humble opinion I would concentrate on using electronic trigger technology, solid state relays and motion validation logic (feedback). The value of doing this is first reliability and secondly immediate system fault identification. You should be able to use a common family of components for all your solutions. Steve Thanks! I have different kinds of equipment for different families of products. Most of my latest posts have been for mechanical equipment. The other equipment I'm addressing is all hydraulic and pneumatic actuated. The relay logic controls the valves. |
#4
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Ladder programs for PLCs
Please remember that if you use solid state relays to drive inductive loads, always use R/C filters across AC loads and back EMF
diodes across DC driven loads. Steve "Buerste" wrote in message ... "Steve Lusardi" wrote in message ... PLCs only make sense when you have sequential events that are dependent on previous events, like motion fault detection. From what I have gleaned from previous postings is that your equipment is mechanically timed. In my humble opinion I would concentrate on using electronic trigger technology, solid state relays and motion validation logic (feedback). The value of doing this is first reliability and secondly immediate system fault identification. You should be able to use a common family of components for all your solutions. Steve Thanks! I have different kinds of equipment for different families of products. Most of my latest posts have been for mechanical equipment. The other equipment I'm addressing is all hydraulic and pneumatic actuated. The relay logic controls the valves. |
#5
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Ladder programs for PLCs
"Buerste" wrote in message ... I want/need to replace a few relay-logic controls with PLCs. Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I should look? A lot of my stuff is old and doesn't have schematics yet alone a flow chart. The guy I had that was very good at this retired and moved to SC. man I hear ya. I used to do A LOT of this stuff. The real key is learning exactly how your machine is working. It can be written up in ladder logic form. I doubt you'll find a tutorial on this. It takes that right combination of person that knows machines and has a lot of PLC programming already under his belt. I was never a ladder logic writer type. But, i could read and follow it if the programmer walked me through it. So, my approach was to really watch the machine and understand it. Write it all down in english. Then double check the ladder BEFORE taking the machine apart and installing the PLC. I'm sure you understand your machines. I'd suggest you hire a fella to interview you and write the ladder logic of what you're got. keying it into the PLC is trivial by comparison. karl |
#6
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Ladder programs for PLCs
"Karl Townsend" wrote in message anews.com... "Buerste" wrote in message ... I want/need to replace a few relay-logic controls with PLCs. Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I should look? A lot of my stuff is old and doesn't have schematics yet alone a flow chart. The guy I had that was very good at this retired and moved to SC. man I hear ya. I used to do A LOT of this stuff. The real key is learning exactly how your machine is working. It can be written up in ladder logic form. I doubt you'll find a tutorial on this. It takes that right combination of person that knows machines and has a lot of PLC programming already under his belt. I was never a ladder logic writer type. But, i could read and follow it if the programmer walked me through it. So, my approach was to really watch the machine and understand it. Write it all down in english. Then double check the ladder BEFORE taking the machine apart and installing the PLC. I'm sure you understand your machines. I'd suggest you hire a fella to interview you and write the ladder logic of what you're got. keying it into the PLC is trivial by comparison. karl One of my engineer's brother's next-door-neighbor's cousin's buddy does this all the time and sells the hardware too. I'll just look over his shoulder and go for the osmosis method. |
#7
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Ladder programs for PLCs
"Buerste" fired this volley in
: I want/need to replace a few relay-logic controls with PLCs. Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I should look? A lot of my stuff is old and doesn't have schematics yet alone a flow chart. The guy I had that was very good at this retired and moved to SC. IF you decide to use a PLC to do this, you can ease your task by choosing one of the types of controller that incorporates a crippled BASIC or BASIC-like programming language that can run behind the ladder. Ladder logic is pretty foreign stuff to someone not schooled in thinking in those terms. It becomes a lot easier for some, if the only things the ladder code has to do is detect conditions, and the actual control is done with a more-or-less easy to understand algorithmic language. I do quite complex hydraulic/pneumatic systems around PLCs; The typical machine has as many as thirty or forty limit and cycle sensing conditions, and fifteen or more directional or proportional control valves. In that sort of environment having a programming language available is a boon. (even if I did have to write my own floating-point library to support the app in an integer-only operating system). LLoyd |
#8
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Ladder programs for PLCs
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message . 3.70... "Buerste" fired this volley in : I want/need to replace a few relay-logic controls with PLCs. Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I should look? A lot of my stuff is old and doesn't have schematics yet alone a flow chart. The guy I had that was very good at this retired and moved to SC. IF you decide to use a PLC to do this, you can ease your task by choosing one of the types of controller that incorporates a crippled BASIC or BASIC-like programming language that can run behind the ladder. Ladder logic is pretty foreign stuff to someone not schooled in thinking in those terms. It becomes a lot easier for some, if the only things the ladder code has to do is detect conditions, and the actual control is done with a more-or-less easy to understand algorithmic language. I just suggested one of these somewhere elsa on the group. They are pretty cheap and are programmed in a sort of Basic like language http://www.splatco.com/controllers.htm I do quite complex hydraulic/pneumatic systems around PLCs; The typical machine has as many as thirty or forty limit and cycle sensing conditions, and fifteen or more directional or proportional control valves. In that sort of environment having a programming language available is a boon. (even if I did have to write my own floating-point library to support the app in an integer-only operating system). LLoyd |
#9
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Ladder programs for PLCs
On Jun 15, 2:34*am, "Grumpy" wrote:
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in messagenews:Xns9D97494D258F8lloydspmindspringcom@2 16.168.3.70... "Buerste" fired this volley in : I want/need to replace a few relay-logic controls with PLCs. Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. *Should be ideal for PLCs. *I need to learn ladder programming. *On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. *Any direction I should look? *A lot of my stuff is old and doesn't have schematics yet alone a flow chart. *The guy I had that was very good at this retired and moved to SC. IF you decide to use aPLCto do this, you can ease your task by choosing one of the types of controller that incorporates a crippled BASIC or BASIC-like programming language that can run behind the ladder. Ladder logic is pretty foreign stuff to someone not schooled in thinking in those terms. *It becomes a lot easier for some, if the only things the ladder code has to do is detect conditions, and the actual control is done with a more-or-less easy to understand algorithmic language. I just suggested one of these somewhere elsa on the group. They are pretty cheap and are programmed in a sort of Basic like languagehttp://www.splatco.com/controllers.htm I do quite complex hydraulic/pneumatic systems around PLCs; *The typical machine has as many as thirty or forty limit and cycle sensing conditions, and fifteen or more directional or proportional control valves. *In that sort of environment having a programming language available is a boon. (even if I did have to write my own floating-point library to support the app in an integer-only operating system). LLoyd- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - I down loaded their help demo tuturial, and got the non working software. Wow, this was too cool. Does any other vendor have this simple of a ladder logic coding software, I never could figure out how to get the automation direct demo to work. The development kit, is a $300 with shipping, for the one with RTC, a little pricy. My first project is to take the manual surface grinder, and install power feeds, and use a PLC to control the surface feed, and cross step. The verticle is a little trickyer as you can't trust that a tenth down, won't jump 2 thou, at least on this 6x12 HF. |
#10
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Ladder programs for PLCs
On Jun 14, 1:04*am, "Buerste" wrote:
I want/need to replace a few relay-logic controls with PLCs. *Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. *Should be ideal for PLCs. *I need to learn ladder programming. *On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. *Any direction I should look? *A lot of my stuff is old and doesn't have schematics yet alone a flow chart. *The guy I had that was very good at this retired and moved to SC. I learned by designing controls with actual relays before PLCs came out. We didn't document other than the schematic, designers and repairmen were expected to stare at it until it all made sense. Once I understood 3-wire control (latching relays) the rest wasn't too bad. This is another approach to understanding event-driven process flow: http://en.wikipedia.org/wiki/State_diagram jsw |
#11
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Ladder programs for PLCs
Jim Wilkins fired this volley in
: On Jun 14, 1:04*am, "Buerste" wrote: I want/need to replace a few relay-logic controls with PLCs. *Typically , a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. *Should be ideal for PLCs. *I need to learn ladder programming. *On the web, the re are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. *Any direction I shou ld look? *A lot of my stuff is old and doesn't have schematics yet alone a flow chart. *The guy I had that was very good at this retired and moved to S C. I learned by designing controls with actual relays before PLCs came out. We didn't document other than the schematic, designers and repairmen were expected to stare at it until it all made sense. Once I understood 3-wire control (latching relays) the rest wasn't too bad. This is another approach to understanding event-driven process flow: http://en.wikipedia.org/wiki/State_diagram jsw Another way one can learn is by purchasing a low-cost PLC and using the associated tools. One family of boards that comes with a compiler and hundreds of programming examples is the TriLogic M-series. Buy an 8x8 (8 in, 8 out) or a 16x16, and you'll have all the power you'd likely need for such a project, along with all the tools and examples to use the device. This series (as do others like it in other manufacturers' catalogs) has PWM and Stepper control routines either built-in or as free libraries. You don't even need a stepper controller, just drivers. The board can handle it all in real-time while running your application. http://www.tri-plc.com/products.htm Look at the M-series for high-power capabilities; all the way down to the Nano and E-series for smaller aps. I have a number of these in hot, humid environments. The oldest is over 6 years running now, with never a down moment due to hardware breakdowns. (a few programming bugs, yes G) LLoyd |
#12
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Ladder programs for PLCs
On Jun 14, 1:32*pm, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote: Jim Wilkins fired this volley : On Jun 14, 1:04 am, "Buerste" wrote: I want/need to replace a few relay-logic controls with PLCs. Typically , a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and *3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, the re are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I shou ld look? A lot of my stuff is old and doesn't have schematics yet alone a *flow chart. The guy I had that was very good at this retired and moved to S C. I learned by designing controls with actual relays before PLCs came out. We didn't document other than the schematic, designers and repairmen were expected to stare at it until it all made sense. Once I understood 3-wire control (latching relays) the rest wasn't too bad. This is another approach to understanding event-driven process flow: http://en.wikipedia.org/wiki/State_diagram jsw Another way one can learn is by purchasing a low-cost PLC and using the associated tools. One family of boards that comes with a compiler and hundreds of programming examples is the TriLogic M-series. Buy an 8x8 (8 in, 8 out) or a 16x16, and you'll have all the power you'd likely need for such a project, along with all the tools and examples to use the device. *This series (as do others like it in other manufacturers' catalogs) has PWM and Stepper control routines either built-in or as free libraries. *You don't even need a stepper controller, just drivers. *The board can handle it all in real-time while running your application. http://www.tri-plc.com/products.htm Look at the M-series for high-power capabilities; all the way down to the Nano and E-series for smaller aps. I have a number of these in hot, humid environments. *The oldest is over 6 years running now, with never a down moment due to hardware breakdowns. * (a few programming bugs, yes G) LLoyd- Hide quoted text - - Show quoted text - One of the best methods I have found to create a ladder logic program from a "new to me" machine is to create a series of "IF ... THEN ..." sentences on a piece of paper. For example: IF "Spindle Start" button is pushed AND "Spindle is not running" THEN "turn on spindle motor" IF "Spindle is Running" AND "Spindle Stop" button is pushed THEN "turn off spindle motor" These types of statements will export very easily to ladder logic diagrams. Keep in mind, these are the basics of PLC programming. There is a world of additional functions that modern PLCs offer... timers/leading-edge events/trailing-edge events/serial IO _kevin |
#13
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Ladder programs for PLCs
On 6/14/2010 1:04 AM, Buerste wrote:
I want/need to replace a few relay-logic controls with PLCs. Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I should look? A lot of my stuff is old and doesn't have schematics yet alone a flow chart. The guy I had that was very good at this retired and moved to SC. Where are you located? I do this regularly with pneumatic systems. |
#14
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Ladder programs for PLCs
On 06/13/2010 10:04 PM, Buerste wrote:
I want/need to replace a few relay-logic controls with PLCs. (snip) The guy I had that was very good at this retired and moved to SC. A bell just went "bing!" in my head -- do you need to find a smart kid who can make this happen under direction? I.e., if you can't _find_ the person to do the job, can you _make_ one? -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com |
#15
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Ladder programs for PLCs
"Buerste" wrote in message ... I want/need to replace a few relay-logic controls with PLCs. Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I should look? A lot of my stuff is old and doesn't have schematics yet alone a flow chart. The guy I had that was very good at this retired and moved to SC. There is a program called logixpro http://thelearningpit.com/lp/logixpro.html You can download the demo version and program and test ladder logic for free. The program is like Allen Bradley RSlogix 500 programming software. It's a cheap way to learn this stuff, unfortunately the actual Allen Bradley software isn't that cheap. You need to decide what PLC's to go with because the learning and software will probably be a larger investment than the hardware that you can probably find on eBay. Years ago Mitsubishi electric was clearing out some of their older controls and I bought a few of them on eBay, they came with programming software. What you have to decide includes do you want 24V DC or 120V AC power to PLC, input voltage, output voltage. Do you have any PLC programming software available now? Relay outputs will work with 24V DC or 120V AC but mechanical relays have less life than solid state transistors (24VDC) or SCR/Triacs(120VAC). I kind of like 24VDC for inputs and 120VAC for outputs, this gives you high speed for inputs and more output power to drive valves, etc. For example, if you have an output card current rating of 2A, that would be up to 48 Watts DC or up to 240 Watts AC for the same current, can help if you're driving multiple valves. If you decide on a PLC I can help you through getting the program to do whatever you want it to. One of the cheapest to get working PLC's is the Automation Direct PLC, but I'm not sure on their quality, not sure if you would be better off with Automation Direct or something else. The modular racks are nice because you can get cards for whatever you want, you can have some AC and some DC input and output cards as you need. If you use a fixed I/O PLC you could use relays to convert between the AC and DC in's and out's. RogerN |
#16
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Ladder programs for PLCs
"Buerste" wrote in message ... I want/need to replace a few relay-logic controls with PLCs. Typically, a machine is using 6 to 8, 3 or 4 pole DT relays, 6 to 8 limit switches and 3 to 4 operator switches, and 4 to 6 hydraulic/pneumatic valves. Should be ideal for PLCs. I need to learn ladder programming. On the web, there are plenty of tutorials but everything I've seen or tried is lacking in translating the real-life process into a program. Any direction I should look? A lot of my stuff is old and doesn't have schematics yet alone a flow chart. The guy I had that was very good at this retired and moved to SC. Give an example of what you want to make a machine do and I and/or others can provide logic. Take it step by step, don't describe the whole operation but just the first step. We can provide sample code to perform the step and you can understand how each step works, and apply it to your machines however you need to. For example, it is common to have a run mode for a machine that is enabled when you press a "Start" pushbutton and latched in until you press the "STOP" button or an E-stop, safety switch, or any sort of interlock is broke. For this you normally wire through contacts so that power is made to the input so the input is ON when it is in the safe condition, that way, if a wire is broke in the safety circuit, the thing stops running. START STOP RUN |----| |----|----| |-----( )--| | | | RUN | |----| |----| This says if the start button is pressed while the stop input is on (safe to run) then the run memory comes on. Once the run memory comes on it branches the start button so the start button doesn't have to be held in. Then you might have something like this: RUN AUTO_SS AUTO_MODE |----| |----|----| |---------( )--| | | AUTO_SS MANUAL_MODE |----|\|---------( )--| OK, then you might have a rung telling when everything is in home position, perhaps the initial position needed for all system go, ready to start. If it is in auto mode and homed, then it can run the automatic cycle. If it is manual position it can be homed with a home button or operated manually as needed. The cycle normally involves a step and detecting when that step is done, often a dwell timer before the next step starts. Eventually this gets back to the position to start the next cycle and it is repeated. You can have a condition for a "Stop at the end of the cycle" to stop the machine without crashing the current cycle. At the end of the automatic cycle, it checks "Stop at end of cycle" and stops or continues operation. I would recommend just starting to update a machine and ask questions when they arise, it seems there are plenty of people on here knowledgeable and willing to help. Once you get walked through one machine you can probably get through 95% of the next machine before you run into something you have a question on. If you know the machine and you know the program, you will be able to modify it for better performance or upgrade the automation, such as interface it to work with an automatic feeder or robots and such. RogerN |
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