tag:blogger.com,1999:blog-77289536254880306862024-02-18T21:19:23.278-08:00PLC, PLC OMRON, PLC MITSUBISHI, PLC SIMULATORIts all about Programmable Logic Controll.Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-7728953625488030686.post-67383233996231703692009-11-17T09:00:00.000-08:002009-11-17T09:00:02.248-08:00Program PLC training: LatchingHow to make Program Latching at PLC, we teach its way by using picture that direct you practices.<br />
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1.How to make program Latching PLC Mitsubishi<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsWcV48S1gBCiGW5a36gr2OI0ERWrDg5opfxxqtrdhxAc-nVBhus7L_aCInIfnjwHkSkDPDwAGvoYrvxhEqSTO5ew1fQmO3ER6zFi_PuD96lSsRvXvMnDeGto6oO0pWL5cyUgkrFusHmPO/s1600-h/PLC+Lacthing+Mitsubishi.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsWcV48S1gBCiGW5a36gr2OI0ERWrDg5opfxxqtrdhxAc-nVBhus7L_aCInIfnjwHkSkDPDwAGvoYrvxhEqSTO5ew1fQmO3ER6zFi_PuD96lSsRvXvMnDeGto6oO0pWL5cyUgkrFusHmPO/s640/PLC+Lacthing+Mitsubishi.JPG" /></a><br />
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2.How to make program Latching PLC Keyence<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhavnX4HAQZRi2vzlMDCigh9KV98qqffiO9ZCjALnmkHu4wg0fnlwDfROgjh1DqCtdOaop3_KZSpH55HgClCLJkEaIFAhynAIEBptJjvDI4lAri-OAnAy6TVgIXU-EfHVZxTe9ZkTACwYWG/s1600-h/PLC+Lacthing+Keyence.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhavnX4HAQZRi2vzlMDCigh9KV98qqffiO9ZCjALnmkHu4wg0fnlwDfROgjh1DqCtdOaop3_KZSpH55HgClCLJkEaIFAhynAIEBptJjvDI4lAri-OAnAy6TVgIXU-EfHVZxTe9ZkTACwYWG/s640/PLC+Lacthing+Keyence.JPG" /></a><br />
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</div><div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com10tag:blogger.com,1999:blog-7728953625488030686.post-87969457302328962412009-11-16T09:00:00.000-08:002009-11-16T09:00:01.680-08:00Program PLC training: timer<div class="separator" style="clear: both; text-align: center;"><br />
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<div align="center"></div>Following we teach way of making program Timer PLC Mitsubishi and Keyence, by using picture, lets may directly be practiced.<br />
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1.How to make Program Timer PLC Mitsubishi.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0x1OKN6D1pUwn5fFJU7UlNpTpEPExnU4QEJ3_NLySiW99TeiSJdtj5XZch6nV_leb6RP6Hb6yMIBi18vcso1YRHB52sYTINDQ5RyFFDOn99ZCY7qgBvWqyIYeI721z6BzzVRr7dQQcNIu/s1600-h/Sample+Timer+Mitsubishi.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0x1OKN6D1pUwn5fFJU7UlNpTpEPExnU4QEJ3_NLySiW99TeiSJdtj5XZch6nV_leb6RP6Hb6yMIBi18vcso1YRHB52sYTINDQ5RyFFDOn99ZCY7qgBvWqyIYeI721z6BzzVRr7dQQcNIu/s640/Sample+Timer+Mitsubishi.JPG" /></a><br />
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</div><div align="left">2.How to make Program Timer PLC Keyence.<br />
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</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrGT7sVOrjUUbaEI-KEJMNxK-2GjKbT10kbBmAJSBwDlChcpzgkgxmcdSg-keISlrt0W-XiGj5ZK71q4XIlmvRAqa0Tc0B8m6SG4rE_pHVYUBj2FghyphenhyphenweEzi5zDnMRr3hhEGebyp922xxI/s1600-h/Sample+Timer+Keyence.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrGT7sVOrjUUbaEI-KEJMNxK-2GjKbT10kbBmAJSBwDlChcpzgkgxmcdSg-keISlrt0W-XiGj5ZK71q4XIlmvRAqa0Tc0B8m6SG4rE_pHVYUBj2FghyphenhyphenweEzi5zDnMRr3hhEGebyp922xxI/s640/Sample+Timer+Keyence.JPG" /></a><br />
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</div><div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com5tag:blogger.com,1999:blog-7728953625488030686.post-44008060422381933222009-11-15T05:45:00.000-08:002009-11-15T05:25:31.522-08:00Timers and Counter function in PLC<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjvvXt0GmvNWW44aHZxrc96JltEXlzKxWK34MFeM5mt_QkZN5ncHStahDgifQob8W4rLfz_7EEToel81DOOBX4F5O_TQVlSJEsoUGLi9n_x0cXYDpQhlwPTIRp5QfGWeAQzrd4-kzd_B5jy/s1600-h/timer.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjvvXt0GmvNWW44aHZxrc96JltEXlzKxWK34MFeM5mt_QkZN5ncHStahDgifQob8W4rLfz_7EEToel81DOOBX4F5O_TQVlSJEsoUGLi9n_x0cXYDpQhlwPTIRp5QfGWeAQzrd4-kzd_B5jy/s320/timer.jpg" /></a><br />
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Timers and counters are indispensable in PLC programming. Industry has to number its products, determine a needed action in time, etc. Timing functions is very important, and cycle periods are critical in many processes. <br />
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There are two types of timers delay-off and delay-on. First is late with turn off and the other runs late in turning on in relation to a signal that activated timers. Example of a delay-off timer would be staircase lighting. Following its activation, it simply turns off after few minutes. <br />
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Each timer has a time basis, or more precisely has several timer basis. Typical values are: 1 second, 0.1 second, and 0,01 second. If programmer has entered .1 as time basis and 50 as a number for delay increase, timer will have a delay of 5 seconds (50 x 0.1 second = 5 seconds). <br />
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Timers also have to have value SV set in advance. Value set in advance or ahead of time is a number of increments that timer has to calculate before it changes the output status. Values set in advance can be constants or variables. If a variable is used, timer will use a real time value of the variable to determine a delay. This enables delays to vary depending on the conditions during function. Example is a system that has produced two different products, each requiring different timing during process itself. Product A requires a period of 10 seconds, so number 10 would be assigned to the variable. When product B appears, a variable can change value to what is required by product B. <br />
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Typically, timers have two inputs. First is timer enable, or conditional input (when this input is activated, timer will start counting). Second input is a reset input. This input has to be in OFF status in order for a timer to be active, or the whole function would be repeated over again. Some PLC models require this input to be low for a timer to be active, other makers require high status (all of them function in the same way basically). However, if reset line changes status, timer erases accumulated value. It can measure from 0 to 999.9 seconds with precision of 0.1 seconds more or less. <br />
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author: Nebojsa Matic<div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com2tag:blogger.com,1999:blog-7728953625488030686.post-56760725139968355492009-11-15T04:56:00.000-08:002009-11-15T04:56:56.892-08:00Connection sensors and execution devices in PLC<div style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><br />
<strong>Introduction </strong><br />
Connecting external devices to a PLC controller regardless whether they are input or output is a special subject matter for industry. If it stands alone, PLC controller itself is nothing. In order to function it needs sensors to obtain information from environment, and it also needs execution devices so it could turn the programmed change into a reality. Similar concept is seen in how human being functions. Having a brain is simply not enough. Humans achieve full activity only with processing of information from a sensor (eyes, ears, touch, smell) and by taking action through hands, legs or some tools. Unlike human being who receives his sensors automatically, when dealing with controllers, sensors have to be subsequently connected to a PLC. How to connect input and output parts is the topic of this chapter. <br />
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<strong>Sinking-Sourcing Concept</strong><br />
</div><div style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;">PLC has input and output lines through which it is connected to a system it directs. Input can be keys, switches, sensors while outputs are led to different devices from simple signalization lights to complex communication modules.<br />
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This is a very important part of the story about PLC controllers because it directly influences what can be connected and how it can be connected to controller inputs or outputs. Two terms most frequently mentioned when discussing connections to inputs or outputs are "sinking" and "sourcing". These two concepts are very important in connecting a PLC correctly with external environment. The most brief definition of these two concepts would be: <br />
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SINKING = Common GND line (-) <br />
SOURCING = Common VCC line (+) <br />
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First thing that catches one's eye are "+" and "-" supply, DC supply. Inputs and outputs which are either sinking or sourcing can conduct electricity only in one direction, so they are only supplied with direct current. According to what we've said thus far, each input or output has its own return line, so 5 inputs would need 10 screw terminals on PLC controller housing. Instead, we use a system of connecting several inputs to one return line as in the following picture. These common lines are usually marked "COMM" on the PLC controller housing. <br />
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<img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEUmXHBCYyrZKqogKuTheT8iQj5xjRGDQm5Q470npghyFQbnvxoatL4xZXKjMkkc8KgVcWhEYrpl5ln45veMp8F03NC7dBgRlFV6E18TTPfRNeTXiZSMLeEheHCcRxBws8o67WVZDfRqXZ/s400/Connection+several+input+to+a+common+line.JPG" /><br />
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<strong>Input lines</strong><br />
Explanation of PLC controller input and output lines has up to now been given only theoretically. In order to apply this knowledge, we need to make it a little more specific. Example can be connection of external device such as proximity sensor. Sensor outputs can be different depending on a sensor itself and also on a particular application. Following pictures display some examples of sensor outputs and their connection with a PLC controller. Sensor output actually marks the size of a signal given by a sensor at its output when this sensor is active. In one case this is +V (supply voltage, usually 12 or 24V) and in other case a GND (0V). Another thing worth mentioning is that sinking-sourcing and sourcing - sinking pairing is always used, and not sourcing-sourcing or sinking-sinking pairing.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSKv-zY5E7aSzGgR3dpPiD-iq00TWJ8sd-nQdNo-80jzGjGd8eAEOs7IOviifpL0fKMroQMOwxGR8at0tonucB-B9l_Ahny8oeLIsnMDyMyOctmhYMMraifnp8MJk4OWdFZYdG93wngNoQ/s1600-h/connection+sensors.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSKv-zY5E7aSzGgR3dpPiD-iq00TWJ8sd-nQdNo-80jzGjGd8eAEOs7IOviifpL0fKMroQMOwxGR8at0tonucB-B9l_Ahny8oeLIsnMDyMyOctmhYMMraifnp8MJk4OWdFZYdG93wngNoQ/s400/connection+sensors.JPG" /></a><br />
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</div>If we were to make type of connection more specific, we'd get combinations as in following pictures (for more specific connection schemas we need to know the exact sensor model and a PLC controller model).<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggYW-MN_8iUstaGlnNw_Gd2DJgFucKLgUZZmbpFaSeE8M5dZ420sLtuWfeTWT8_UARaJYuTRDMTi6lFGgtOYh8PbREgwi4QbWGetC7G9soODy26naX6akd687LhnqJP0BV5fnEx-za6K6V/s1600-h/connection+sensors+Transistor.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggYW-MN_8iUstaGlnNw_Gd2DJgFucKLgUZZmbpFaSeE8M5dZ420sLtuWfeTWT8_UARaJYuTRDMTi6lFGgtOYh8PbREgwi4QbWGetC7G9soODy26naX6akd687LhnqJP0BV5fnEx-za6K6V/s640/connection+sensors+Transistor.JPG" /></a><br />
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</div><strong>Output lines </strong><br />
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PLC controller output lines usually can be:<br />
-transistors in PNP connection<br />
-transistors in NPN connection<br />
-relays <br />
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The following two pictures display a realistic way how a PLC manages external devices. It ought to be noted that a main difference between these two pictures is a position of "output load device". By "output load device" we mean some relay, signalization light or similar.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiF9HiqjgJyNZSIEKmSvV2v7qbFs9cQaVOx_zYUfrz4DSScEu11USFDioMhYZS45k8qdEVcNK2r0xww3zDzzkWpNcrcfVY1xyn0vQs7cdutkTUWoEo8MmD1oYqPeNQPW75wTfCM8SAf0vG7/s1600-h/Connection+output.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiF9HiqjgJyNZSIEKmSvV2v7qbFs9cQaVOx_zYUfrz4DSScEu11USFDioMhYZS45k8qdEVcNK2r0xww3zDzzkWpNcrcfVY1xyn0vQs7cdutkTUWoEo8MmD1oYqPeNQPW75wTfCM8SAf0vG7/s640/Connection+output.JPG" /></a><br />
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How something is connected with a PLC output depends on the element being connected. In short, it depends on whether this element of output load device is activated by a positive supply pole or a negative supply pole.<br />
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author: Nebojsa Matic<div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com1tag:blogger.com,1999:blog-7728953625488030686.post-18584342089147790682009-11-15T04:43:00.000-08:002009-11-15T04:43:21.210-08:00Mechanical system in PLCThere are two mechanic design types used occasionally for system-sistem PLC : Single box Type , and Type Modular and Rak. Single box type generally applied for small fairish controller of which can be programmed and marketed in the form of inwrought packaging, complete with energy?power allowance, processor, memory, and units input/output. See picture under<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhXEIDlfOFMBwjuVHWdR_2pphq4yi0Ku1DxgGhgP3xwvD-DO5CT__fhvn6xHU2u0lmct7HABA1SjYS4pfiM10wA0Ee7XOruqpzZOwh6-0-lf6OJuE8bKAv3KRKQYSM2kFoNL4TYXt493CuS/s1600-h/type+single.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhXEIDlfOFMBwjuVHWdR_2pphq4yi0Ku1DxgGhgP3xwvD-DO5CT__fhvn6xHU2u0lmct7HABA1SjYS4pfiM10wA0Ee7XOruqpzZOwh6-0-lf6OJuE8bKAv3KRKQYSM2kFoNL4TYXt493CuS/s320/type+single.JPG" /></a><br />
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</div>Usually, a kind of this PLC type can have 40 point of input/output and an memory unit which storage can around 300 to 1000 instructions. <br />
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Modular type consisted of modules that is separate, his(its each to ration energy?power, processor, other modules, often stuck into at rail lines in a base. Rack Type can be utilized for all controller measure program and has multifarious tidy functional unit for independent modules of which can be stuck into socket-socket at a base is in the form of Rak. See picture under ;<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzkV3aGDcGlUff62JAO1LoNnx3jgMIYco-JeTFVWYODozqVFAe69Tv2vxO7vJFs-nAcplTW_M6xuhyphenhyphenRo0u1Oz_uKvKt1KULSn01_gFCtOij8XL2T7tHtffHpoLff0Nxx3JGXQwTKMRu3A5/s1600-h/modular+type+and+rack+type.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzkV3aGDcGlUff62JAO1LoNnx3jgMIYco-JeTFVWYODozqVFAe69Tv2vxO7vJFs-nAcplTW_M6xuhyphenhyphenRo0u1Oz_uKvKt1KULSn01_gFCtOij8XL2T7tHtffHpoLff0Nxx3JGXQwTKMRu3A5/s320/modular+type+and+rack+type.JPG" /></a><br />
</div>Combination of Module needed to a the application of certain determined by user and modules selected then stuck at rack. Because of item relative easy for we to add number of extensions input/output with simply sticking additional modules or enlarge memory measure with simply sticking addition memory units. <br />
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Programs packed into one of memory PLC by using a programming peripheral generally is not jointed permanently to PLC and movable out of one controllers to other controllers without disturbing operations is being implemented. Oparation to PLC , programming peripheral is not necessarily be jointed to PLC because this peripheral will only remove program which we are create to memory PLC. <br />
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Supplier PLC : Mitsubishi, Keyence, Omron, Siemens, Atos, Festo, Honeywell, Schneider Electric, Allen Bradley, IDEC, ABB, Rockwell Automation, General Electric, and etc.<div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com1tag:blogger.com,1999:blog-7728953625488030686.post-1801069122869388052009-11-15T04:32:00.000-08:002009-11-15T04:32:41.167-08:00How does PLC works<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicm9-KWgZYTPRzTqeu803sCyUBb3UAc745wCGikmIzDzOaP9zIUt3ik7fp_qhvSxwSS7nRjqqj-hoYb_jKZzImVhMz6IIzmYRC3xxleUWebIMdOWPmzmPNm1gK-1GKyBzpMgzRyz2JRl5l/s1600-h/IO+Update.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicm9-KWgZYTPRzTqeu803sCyUBb3UAc745wCGikmIzDzOaP9zIUt3ik7fp_qhvSxwSS7nRjqqj-hoYb_jKZzImVhMz6IIzmYRC3xxleUWebIMdOWPmzmPNm1gK-1GKyBzpMgzRyz2JRl5l/s400/IO+Update.JPG" /></a><br />
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Basis of a PLC function is continual scanning of a program. Under scanning we mean running through all conditions within a guaranteed period. Scanning process has three basic steps:<br />
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<strong>Step 1.</strong><br />
Testing input status. First, a PLC checks each of the inputs with intention to see which one of them has status ON or OFF. In other words, it checks whether a sensor, or a switch etc. connected with an input is activated or not. Information that processor thus obtains through this step is stored in memory in order to be used in the following step.<br />
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<strong>Step 2. </strong><br />
Program execution. Here a PLC executes a program, instruction by instruction. Based on a program and based on the status of that input as obtained in the preceding step, an appropriate action is taken. This reaction can be defined as activation of a certain output, or results can be put off and stored in memory to be retrieved later in the following step.<br />
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<strong>Step 3. </strong><br />
Checkup and correction of output status. Finally, a PLC checks up output status and adjusts it as needed. Change is performed based on the input status that had been read during the first step, and based on the results of program execution in step two. Following the execution of step 3 PLC returns to the beginning of this cycle and continually repeats these steps. Scanning time is defined by the time needed to perform these three steps, and sometimes it is an important program feature.<div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com1tag:blogger.com,1999:blog-7728953625488030686.post-68582853774169082552009-11-12T02:34:00.001-08:002009-11-12T03:10:10.637-08:00Ladder diagram to PLC programmingPLC Introduction<br />
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Programmable controllers are generally programmed in ladder diagram (or "relay diagram") which is nothing but a symbolic representation of electric circuits. Symbols were selected that actually looked similar to schematic symbols of electric devices, and this has made it much easier for electricians to switch to programming PLC controllers. Electrician who has never seen a PLC can understand a ladder diagram. <br />
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Ladder diagram <br />
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There are several languages designed for user communication with a PLC, among which ladder diagram is the most popular. Ladder diagram consists of one vertical line found on the left hand side, and lines which branch off to the right. Line on the left is called a "bus bar", and lines that branch off to the right are instruction lines. Conditions which lead to instructions positioned at the right edge of a diagram are stored along instruction lines. Logical combination of these conditions determines when and in what way instruction on the right will execute. Basic elements of a relay diagram can be seen in the following picture. <br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4q8-DoWvNSrRF8Tv1jjbEgQ4dSp45h_FRS6YWnCxRIj1yAVHUlo5X-WRYT_BqunDgCnqyUzl2M7PZMlNYJ01_DVQX5Ickk4zGx6Bgy3YTlMkC17urxYwcJBIOaST4Nwia800Hm9eKdNON/s1600-h/relay+diagram.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4q8-DoWvNSrRF8Tv1jjbEgQ4dSp45h_FRS6YWnCxRIj1yAVHUlo5X-WRYT_BqunDgCnqyUzl2M7PZMlNYJ01_DVQX5Ickk4zGx6Bgy3YTlMkC17urxYwcJBIOaST4Nwia800Hm9eKdNON/s640/relay+diagram.JPG" /></a><br />
</div>Most instructions require at least one operand, and often more than one. Operand can be some memory location, one memory location bit, or some numeric value -number.In a case when we wish to proclaim a constant as an operand, designation # is used beneath the numeric writing (for a compiler to know it is a constant and not an address.) <br />
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Based on the picture above, one should note that a ladder diagram consists of two basic parts: left section also called conditional, and a right section which has instructions. When a condition is fulfilled, instruction is executed, and that's all! <br />
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</div>Picture above represents a example of a ladder diagram where relay is activated in PLC controller when signal appears at input line 0. Vertical line pairs are called conditions. Each condition in a ladder diagram has a value ON or OFF, depending on a bit status assigned to it. In this case, this bit is also physically present as an input line (screw terminal) to a PLC controller. If a key is attached to a corresponding screw terminal, you can change bit status from a logic one status to a logic zero status, and vice versa. Status of logic one is usually designated as "ON", and status of logic zero as "OFF". <br />
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Right section of a ladder diagram is an instruction which is executed if left condition is fulfilled. There are several types of instructions that could easily be divided into simple and complex. Example of a simple instruction is activation of some bit in memory location. In the example above, this bit has physical connotation because it is connected with a relay inside a PLC controller. When a CPU activates one of the leading four bits 10, relay contacts move and connect lines attached to it. In this case, these are the lines connected to a screw terminal marked as 0 and to one of COM screw terminals. <br />
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Normally open and normally closed contacts <br />
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Since we frequently meet with concepts "normally open" and "normally closed" in industrial environment, it's important to know them. Both terms apply to words such as contacts, input, output, etc. (all combinations have the same meaning whether we are talking about input, output, contact or something else). <br />
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Principle is quite simple, normally open switch won't conduct electricity until it is pressed down, and normally closed switch will conduct electricity until it is pressed. Good examples for both situations are the doorbell and a house alarm. <br />
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If a normally closed switch is selected, bell will work continually until someone pushes the switch. By pushing a switch, contacts are opened and the flow of electricity towards the bell is interrupted. Of course, system so designed would not in any case suit the owner of the house. A better choice would certainly be a normally open switch. This way bell wouldn't work until someone pushed the switch button and thus informed of his or her presence at the entrance. <br />
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Home alarm system is an example of an application of a normally closed switch. Let's suppose that alarm system is intended for surveillance of the front door to the house. One of the ways to "wire" the house would be to install a normally open switch from each door to the alarm itself (precisely as with a bell switch). Then, if the door was opened, this would close the switch, and an alarm would be activated. This system could work, but there would be some problems with this, too. Let's suppose that switch is not working, that a wire is somehow disconnected, or a switch is broken, etc. (there are many ways in which this system could become dysfunctional). The real trouble is that a homeowner would not know that a system was out of order. A burglar could open the door, a switch would not work, and the alarm would not be activated. Obviously, this isn't a good way to set up this system. System should be set up in such a way so the alarm is activated by a burglar, but also by its own dysfunction, or if any of the components stopped working. (A homeowner would certainly want to know if a system was dysfunctional). Having these things in mind, it is far better to use a switch with normally closed contacts which will detect an unauthorized entrance (opened door interrupts the flow of electricity, and this signal is used to activate a sound signal), or a failure on the system such as a disconnected wire. These considerations are even more important in industrial environment where a failure could cause injury at work. One such example where outputs with normally closed contacts are used is a safety wall with trimming machines. If the wall doors open, switch affects the output with normally closed contacts and interrupts a supply circuit. This stops the machine and prevents an injury. <br />
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Concepts normally open and normally closed can apply to sensors as well. Sensors are used to sense the presence of physical objects, measure some dimension or some amount. For instance, one type of sensors can be used to detect presence of a box on an industry transfer belt. Other types can be used to measure physical dimensions such as heat, etc. Still, most sensors are of a switch type. Their output is in status ON or OFF depending on what the sensor "feels". Let's take for instance a sensor made to feel metal when a metal object passes by the sensor. For this purpose, a sensor with a normally open or a normally closed contact at the output could be used. If it were necessary to inform a PLC each time an object passed by the sensor, a sensor with a normally open output should be selected. Sensor output would set off only if a metal object were placed right before the sensor. A sensor would turn off after the object has passed. PLC could then calculate how many times a normally open contact was set off at the sensor output, and would thus know how many metal objects passed by the sensor. <br />
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Concepts normally open and normally closed contact ought to be clarified and explained in detail in the example of a PLC controller input and output. The easiest way to explain them is in the example of a relay. <br />
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</div>Normally open contacts would represent relay contacts that would perform a connection upon receipt of a signal. Unlike open contacts, with normally closed contacts signal will interrupt a contact, or turn a relay off. Previous picture shows what this looks like in practice. First two relays are defined as normally open , and the other two as normally closed. All relays react to a signal! First relay (10) has a signal and closes its contacts. Second relay (11) does not have a signal and remains opened. Third relay (12) has a signal and opens its contacts considering it is defined as a closed contact. Fourth relay (13) does not have a signal and remains closed because it is so defined. <br />
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Concepts "normally open" and "normally closed" can also refer to inputs of a PLC controller. Let's use a key as an example of an input to a PLC controller. Input where a key is connected can be defined as an input with open or closed contacts. If it is defined as an input with normally open contact, pushing a key will set off an instruction found after the condition. In this case it will be an activation of a relay 0. <br />
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If input is defined as an input with normally closed contact, pushing the key will interrupt instruction found after the condition. In this case, this will cause deactivation of relay 0 (relay is active until the key is pressed). You can see in picture below how keys are connected, and view the relay diagrams in both cases. <br />
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</div>Normally open/closed conditions differ in a ladder diagram by a diagonal line across a symbol. What determines an execution condition for instruction is a bit status marked beneath each condition on instruction line. Normally open condition is ON if its operand bit has ON status, or its status is OFF if that is the status of its operand bit. Normally closed condition is ON when its operand bit is OFF, or it has OFF status when the status of its operand bit is ON. <br />
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When programming with a ladder diagram, logical combination of ON and OFF conditions set before the instruction determines the eventual condition under which the instruction will be, or will not be executed. This condition, which can have only ON or OFF values is called instruction execution condition. Operand assigned to any instruction in a relay diagram can be any bit. This means that conditions in a relay diagram can be determined by a status of I/O bits, operational bits, timers/counters, etc. <br />
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author: Nebojsa Matic<div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com0tag:blogger.com,1999:blog-7728953625488030686.post-11331473308754595892009-11-12T02:00:00.000-08:002009-11-12T02:48:23.756-08:00Programmable Logic Controll (PLC)<div class="separator" style="clear: both; text-align: center;"><a href="http://upload.wikimedia.org/wikipedia/commons/2/2c/Automate_siemens_codeur_analyseur_de_trame.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="http://upload.wikimedia.org/wikipedia/commons/2/2c/Automate_siemens_codeur_analyseur_de_trame.JPG" width="400" /></a><br />
</div>A <b>programmable logic controller</b> (<b>PLC</b>) or <b>programmable controller</b> is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result.<br />
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source : wikipedia<div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com2tag:blogger.com,1999:blog-7728953625488030686.post-74752027162409731532009-11-11T03:11:00.000-08:002009-11-12T03:13:00.361-08:00Introduction to Programmable Logic Controllers<span style="color: black; font-family: arial; font-size: small;">Industry has begin to recognize the need for quality improvement and increase in productivity in the sixties and seventies. Flexibility also became a major concern (ability to change a process quickly became very important in order to satisfy consumer needs). <br />
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Try to imagine automated industrial production line in the sixties and seventies. There was always a huge electrical board for system controls, and not infrequently it covered an entire wall! Within this board there was a great number of interconnected electromechanical relays to make the whole system work. By word "connected" it was understood that electrician had to connect all relays manually using wires! An engineer would design logic for a system, and electricians would receive a schematic outline of logic that they had to implement with relays. These relay schemas often contained hundreds of relays. The plan that electrician was given was called "ladder schematic". Ladder displayed all switches, sensors, motors, valves, relays, etc. found in the system. Electrician's job was to connect them all together. One of the problems with this type of control was that it was based on mechanical relays. Mechanical instruments were usually the weakest connection in the system due to their moveable parts that could wear out. If one relay stopped working, electrician would have to examine an entire system (system would be out until a cause of the problem was found and corrected). <br />
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The other problem with this type of control was in the system's break period when a system had to be turned off, so connections could be made on the electrical board. If a firm decided to change the order of operations (make even a small change), it would turn out to be a major expense and a loss of production time until a system was functional again. <br />
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It's not hard to imagine an engineer who makes a few small errors during his project. It is also conceivable that electrician has made a few mistakes in connecting the system. Finally, you can also imagine having a few bad components. The only way to see if everything is all right is to run the system. As systems are usually not perfect with a first try, finding errors was an arduous process. You should also keep in mind that a product could not be made during these corrections and changes in connections. System had to be literally disabled before changes were to be performed. That meant that the entire production staff in that line of production was out of work until the system was fixed up again. Only when electrician was done finding errors and repairing,, the system was ready for production. Expenditures for this kind of work were too great even for well-to-do companies. </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> First Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> "General Motors" is among the first who recognized a need to replace the system's "wired" control board. Increased competition forced auto-makers to improve production quality and productivity. Flexibility and fast and easy change of automated lines of production became crucial! General Motors' idea was to use for system logic one of the microcomputers (these microcomputers were as far as their strength beneath today's eight-bit microcontrollers) instead of wired relays. Computer could take place of huge, expensive, inflexible wired control boards. If changes were needed in system logic or in order of operations, program in a microcomputer could be changed instead of rewiring of relays. Imagine only what elimination of the entire period needed for changes in wiring meant then. Today, such thinking is but common, then it was revolutionary! <br />
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Everything was well thought out, but then a new problem came up of how to make electricians accept and use a new device. Systems are often quite complex and require complex programming. It was out of question to ask electricians to learn and use computer language in addition to other job duties. General Motors Hidromatic Division of this big company recognized a need and wrote out project criteria for first programmable logic controller ( there were companies which sold instruments that performed industrial control, but those were simple sequential controllers û not PLC controllers as we know them today). Specifications required that a new device be based on electronic instead of mechanical parts, to have flexibility of a computer, to function in industrial environment (vibrations, heat, dust, etc.) and have a capability of being reprogrammed and used for other tasks. The last criteria was also the most important, and a new device had to be programmed easily and maintained by electricians and technicians. When the specification was done, General Motors looked for interested companies, and encouraged them to develop a device that would meet the specifications for this project. <br />
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"Gould Modicon" developed a first device which met these specifications. The key to success with a new device was that for its programming you didn't have to learn a new programming language. It was programmed so that same language ûa ladder diagram, already known to technicians was used. Electricians and technicians could very easily understand these new devices because the logic looked similar to old logic that they were used to working with. Thus they didn't have to learn a new programming language which (obviously) proved to be a good move. <em>PLC</em> controllers were initially called PC controllers (programmable controllers). This caused a small confusion when Personal Computers appeared. To avoid confusion, a designation PC was left to computers, and programmable controllers became programmable logic controllers. First <em>PLC</em> controllers were simple devices. They connected inputs such as switches, digital sensors, etc., and based on internal logic they turned output devices on or off. When they first came up, they were not quite suitable for complicated controls such as temperature, position, pressure, etc. However, throughout years, makers of <em>PLC</em> controllers added numerous features and improvements. Today's <em>PLC</em> controller can handle highly complex tasks such as position control, various regulations and other complex applications. The speed of work and easiness of programming were also improved. Also, modules for special purposes were developed, like communication modules for connecting several <em>PLC</em> controllers to the net. Today it is difficult to imagine a task that could not be handled by a <em>PLC</em>. </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Components of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> <em>PLC</em> is actually an industrial microcontroller system (in more recent times we meet processors instead of microcontrollers) where you have hardware and software specifically adapted to industrial environment. Block schema with typical components which <em>PLC</em> consists of is found in the following picture. Special attention needs to be given to input and output, because in these blocks you find protection needed in isolating a CPU blocks from damaging influences that industrial environment can bring to a CPU via input lines. Program unit is usually a computer used for writing a program (often in ladder diagram). </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Central Processing Unit – CPU of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> Central Processing Unit (CPU) is the brain of a <em>PLC</em> controller. CPU itself is usually one of the microcontrollers. Aforetime these were 8-bit microcontrollers such as 8051, and now these are 16- and 32-bit microcontrollers. Unspoken rule is that you'll find mostly Hitachi and Fujicu microcontrollers in <em>PLC</em> controllers by Japanese makers, Siemens in European controllers, and Motorola microcontrollers in American ones. CPU also takes care of communication, interconnectedness among other parts of <em>PLC</em> controller, program execution, memory operation, overseeing input and setting up of an output. <em>PLC</em> controllers have complex routines for memory checkup in order to ensure that <em>PLC</em> memory was not damaged (memory checkup is done for safety reasons). Generally speaking, CPU unit makes a great number of check-ups of the <em>PLC</em> controller itself so eventual errors would be discovered early. You can simply look at any <em>PLC</em> controller and see that there are several indicators in the form of light diodes for error signalization. </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Memory of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> System memory (today mostly implemented in FLASH technology) is used by a <em>PLC</em> for an process control system. Aside from this operating system it also contains a user program translated from a ladder diagram to a binary form. FLASH memory contents can be changed only in case where user program is being changed. <em>PLC</em> controllers were used earlier instead of FLASH memory and have had EPROM memory instead of FLASH memory which had to be erased with UV lamp and programmed on programmers. With the use of FLASH technology this process was greatly shortened. Reprogramming a program memory is done through a serial cable in a program for application development. <br />
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User memory is divided into blocks having special functions. Some parts of a memory are used for storing input and output status. The real status of an input is stored either as "1" or as "0" in a specific memory bit. Each input or output has one corresponding bit in memory. Other parts of memory are used to store variable contents for variables used in user program. For example, timer value, or counter value would be stored in this part of the memory. </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Programming of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> <em>PLC</em> controller can be reprogrammed through a computer (usual way), but also through manual programmers (consoles). This practically means that each <em>PLC</em> controller can programmed through a computer if you have the software needed for programming. Today's transmission computers are ideal for reprogramming a <em>PLC</em> controller in factory itself. This is of great importance to industry. Once the system is corrected, it is also important to read the right program into a PLC again. It is also good to check from time to time whether program in a <em>PLC</em> has not changed. This helps to avoid hazardous situations in factory rooms (some automakers have established communication networks which regularly check programs in <em>PLC</em> controllers to ensure execution only of good programs). <br />
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Almost every program for programming a <em>PLC</em> controller possesses various useful options such as: forced switching on and off of the system inputs/ouputs (I/O lines), program follow up in real time as well as documenting a diagram. This documenting is necessary to understand and define failures and malfunctions. Programmer can add remarks, names of input or output devices, and comments that can be useful when finding errors, or with system maintenance. Adding comments and remarks enables any technician (and not just a person who developed the system) to understand a ladder diagram right away. Comments and remarks can even quote precisely part numbers if replacements would be needed. This would speed up a repair of any problems that come up due to bad parts. The old way was such that a person who developed a system had protection on the program, so nobody aside from this person could understand how it was done. Correctly documented ladder diagram allows any technician to understand thoroughly how system functions. </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Power supply of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> Electrical supply is used in bringing electrical energy to central processing unit. Most <em>PLC</em> controllers work either at 24 VDC or 220 VAC. On some <em>PLC</em> controllers you'll find electrical supply as a separate module. Those are usually bigger <em>PLC</em> controllers, while small and medium series already contain the supply module. User has to determine how much current to take from I/O module to ensure that electrical supply provides appropriate amount of current. Different types of modules use different amounts of electrical current. <br />
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This electrical supply is usually not used to start external inputs or outputs. User has to provide separate supplies in starting <em>PLC</em> controller inputs or outputs because then you can ensure so called "pure" supply for the <em>PLC</em> controller. With pure supply we mean supply where industrial environment can not affect it damagingly. Some of the smaller PLC controllers supply their inputs with voltage from a small supply source already incorporated into a PLC. </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Inputs of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> Intelligence of an automated system depends largely on the ability of a <em>PLC</em> controller to read signals from different types of sensors and input devices. Keys, keyboards and by functional switches are a basis for man versus machine relationship. On the other hand, in order to detect a working piece, view a mechanism in motion, check pressure or fluid level you need specific automatic devices such as proximity sensors, marginal switches, photoelectric sensors, level sensors, etc. Thus, input signals can be logical (on/off) or analogue. Smaller <em>PLC</em> controllers usually have only digital input lines while larger also accept analogue inputs through special units attached to <em>PLC</em> controller. One of the most frequent analogue signals are a current signal of 4 to 20 mA and milivolt voltage signal generated by various sensors. Sensors are usually used as inputs for <em>PLC</em>s. You can obtain sensors for different purposes. They can sense presence of some parts, measure temperature, pressure, or some other physical dimension, etc. (ex. inductive sensors can register metal objects). <br />
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Other devices also can serve as inputs to PLC controller. Intelligent devices such as robots, video systems, etc. often are capable of sending signals to <em>PLC</em> controller input modules (robot, for instance, can send a signal to <em>PLC</em> controller input as information when it has finished moving an object from one place to the other.) </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Input adjustment interface of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> Adjustment interface also called an interface is placed between input lines and a CPU unit. The purpose of adjustment interface to protect a CPU from disproportionate signals from an outside world. Input adjustment module turns a level of real logic to a level that suits CPU unit (ex. input from a sensor which works on 24 VDC must be converted to a signal of 5 VDC in order for a CPU to be able to process it). This is typically done through opto-isolation, and this function you can view in the following picture. Opto-isolation means that there is no electrical connection between external world and CPU unit. They are "optically" separated, or in other words, signal is transmitted through light. The way this works is simple. External device brings a signal which turns LED on, whose light in turn incites photo transistor which in turn starts conducting, and a CPU sees this as logic zero (supply between collector and transmitter falls under 1V). When input signal stops LED diode turns off, transistor stops conducting, collector voltage increases, and CPU receives logic 1 as information. </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Output of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;">Automated system is incomplete if it is not connected with some output devices. Some of the most frequently used devices are motors, solenoids, relays, indicators, sound signalization and similar. By starting a motor, or a relay, <em>PLC</em> can manage or control a simple system such as system for sorting products all the way up to complex systems such as service system for positioning head of CNC machine. Output can be of analogue or digital type. Digital output signal works as a switch; it connects and disconnects line. Analogue output is used to generate the analogue signal (ex. motor whose speed is controlled by a voltage that corresponds to a desired speed). </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Output adjustment interface of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> Output interface is similar to input interface. CPU brings a signal to LED diode and turns it on. Light incites a photo transistor which begins to conduct electricity, and thus the voltage between collector and emmiter falls to 0.7V , and a device attached to this output sees this as a logic zero. Inversely it means that a signal at the output exists and is interpreted as logic one. Photo transistor is not directly connected to a PLC controller output. Between photo transistor and an output usually there is a relay or a stronger transistor capable of interrupting stronger signals. </span><br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjtHYjtmCB6e_TLWnvx_bqcVvg0OBMK8lcNsMzWLyqc7Fk7Gwn0JBJsWPvYoRFje8-tP9nUTjVgkTGyuDHwzbKGAkTELSPL6j-P6g_28o8ELUUmsuTIY8OvysKR7FFepf9dDQEeRqcBSo4/s1600-h/Output+Adjustable+Interface+of+PLC.JPG"><img alt="PLC" border="0" id="BLOGGER_PHOTO_ID_5316973078534662514" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjtHYjtmCB6e_TLWnvx_bqcVvg0OBMK8lcNsMzWLyqc7Fk7Gwn0JBJsWPvYoRFje8-tP9nUTjVgkTGyuDHwzbKGAkTELSPL6j-P6g_28o8ELUUmsuTIY8OvysKR7FFepf9dDQEeRqcBSo4/s320/Output+Adjustable+Interface+of+PLC.JPG" style="cursor: pointer; display: block; height: 138px; margin: 0px auto 10px; text-align: center; width: 320px;" /></a> <br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> Extension lines of Programmable Logic Controllers ( <em>PLC</em> ) </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> Every <em>PLC</em> controller has a limited number of input/output lines. If needed this number can be increased through certain additional modules by system extension through extension lines. Each module can contain extension both of input and output lines. Also, extension modules can have inputs and outputs of a different nature from those on the <em>PLC</em> controller (ex. in case relay outputs are on a controller, transistor outputs can be on an extension module). </span><br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> PLC controller output lines </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> Aside from transistor outputs in PNP and NPN connections, <em>PLC</em> can also have relays as outputs. Existence of relays as outputs makes it easier to connect with external devices. There a 4 relays whose functional contacts are taken out on a <em>PLC</em> controller housing in the form of screw terminals. In reality this looks as in picture below. </span><br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjR5qrLWBLfn4GFyqvcbr_38jxtSgdUImWCBSFkhxVV9yU1VJMuCW_k38Varh7YG1CjU0Yb1_K-5DuPm4UzMDV4iJFiAWGYQU0RjWxYKHPapUAJlqRNgyCqC3f5MClL1dSW7Dgb1TPyME/s1600-h/relay+output.JPG"><img alt="PLC" border="0" id="BLOGGER_PHOTO_ID_5316973447872263154" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjR5qrLWBLfn4GFyqvcbr_38jxtSgdUImWCBSFkhxVV9yU1VJMuCW_k38Varh7YG1CjU0Yb1_K-5DuPm4UzMDV4iJFiAWGYQU0RjWxYKHPapUAJlqRNgyCqC3f5MClL1dSW7Dgb1TPyME/s320/relay+output.JPG" style="cursor: pointer; display: block; height: 312px; margin: 0px auto 10px; text-align: center; width: 320px;" /></a> <br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZ4OYTCSb9_d5uixJ-hJsJo-LBsC4IbtCB1QOXntzMas_9NwB4SaXfCeroTwykFmrGvZ_NrERLHlXulMnChSjSgTMKMU1yCWqJ45WPHAhJvXK5fkL34mnCNZwNZC8CNEhNgbN0UGq2NyM/s1600-h/connection+4+devices+on+relay+output.JPG"><img alt="PLC" border="0" id="BLOGGER_PHOTO_ID_5316973631718358994" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZ4OYTCSb9_d5uixJ-hJsJo-LBsC4IbtCB1QOXntzMas_9NwB4SaXfCeroTwykFmrGvZ_NrERLHlXulMnChSjSgTMKMU1yCWqJ45WPHAhJvXK5fkL34mnCNZwNZC8CNEhNgbN0UGq2NyM/s320/connection+4+devices+on+relay+output.JPG" style="cursor: pointer; display: block; height: 257px; margin: 0px auto 10px; text-align: center; width: 320px;" /></a> <br />
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<span style="color: #0066cc; font-family: arial; font-size: medium;"><u> <em>PLC</em> controller input lines </u></span> <br />
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<span style="color: black; font-family: arial; font-size: small;"> Different sensors, keys, switches and other elements that can change status of a joined bit at <em>PLC</em> input can be hooked up to the <em>PLC</em> controller inputs. In order to realize a change, we need a voltage source to incite an input. The simplest possible input would be a common key. Source of direct voltage of 24V, the same source can be used to incite input (problem with this source is its maximum current which it can give continually and which in our case amounts to 0.2A). Since inputs to a <em>PLC</em> are not big consumers (unlike some sensor where a stronger external supply must be used) it is possible to take advantage of the existing source of direct supply to incite all six keys. </span><br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5ZyLB2VgLgeZglnbFt-zE08eDvyMCi53yZmPs8OQxYHYw-3IbykT8KZG-nBbh7_IHS82fSm6zt-d7vsH5r3qURYFG6sBhudVyNvyC7-JJUG8ZMlAX_MQ4JhC8gb9ecV0tU53UyrgRpJw/s1600-h/plc+input+lines.JPG"><img alt="PLC" border="0" id="BLOGGER_PHOTO_ID_5316973841802895090" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh5ZyLB2VgLgeZglnbFt-zE08eDvyMCi53yZmPs8OQxYHYw-3IbykT8KZG-nBbh7_IHS82fSm6zt-d7vsH5r3qURYFG6sBhudVyNvyC7-JJUG8ZMlAX_MQ4JhC8gb9ecV0tU53UyrgRpJw/s320/plc+input+lines.JPG" style="cursor: pointer; display: block; height: 320px; margin: 0px auto 10px; text-align: center; width: 233px;" /></a> <br />
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author: Nebojsa Matic<div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com2tag:blogger.com,1999:blog-7728953625488030686.post-75444467432334841352009-08-08T20:15:00.000-07:002009-11-16T00:44:52.376-08:00Logo of Programing-PLC.blogspot.comThis is it,<br />
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</div><div class="blogger-post-footer">A complete tutorial and software in PLC Programming</div>Ridwanhttp://www.blogger.com/profile/07735159476826548107noreply@blogger.com0