{"id":19982,"date":"2022-08-16T07:19:47","date_gmt":"2022-08-16T07:19:47","guid":{"rendered":"https:\/\/mdr.foobrdigital.com\/?p=6568"},"modified":"2022-08-16T07:19:47","modified_gmt":"2022-08-16T07:19:47","slug":"main-parts-of-a-plc","status":"publish","type":"post","link":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/2022\/08\/16\/main-parts-of-a-plc\/","title":{"rendered":"Main Parts of a PLC:"},"content":{"rendered":"\n<p>First, we have the input modules or field sensors<strong>.&nbsp;<\/strong>These are the physical connections between the outside world and the PLC. These can be:<\/p>\n\n\n\n<p><strong>Digital<\/strong>&nbsp;inputs, such as<\/p>\n\n\n\n<ul><li>Simple On \u2013 Off switches<\/li><li>Bi metallic temperature strips<\/li><li>Presence or motion sensors<\/li><li>Or even a Float switch<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image\"><a href=\"https:\/\/theengineeringmindset.com\/wp-content\/uploads\/2021\/02\/5-2.png\"><img decoding=\"async\" src=\"https:\/\/theengineeringmindset.com\/wp-content\/uploads\/2021\/02\/5-2.png\" alt=\"\" class=\"wp-image-6151\"\/><\/a><figcaption>Digital Inputs<\/figcaption><\/figure>\n\n\n\n<p>These digital inputs can only provide information on whether something in on or off, nothing in between. For that we would need an&nbsp;<strong>Analogue input.<\/strong>&nbsp;For example a simple control knob which ranges from 0% to 100%. This will go through a voltage transformer to give 0v at 0% and 10v at 100%. The PLC can scale the input to match the \u2018sensitivity\u2019 required for very accurate output control.<\/p>\n\n\n\n<p>It could also convert the voltage into current using a resistor and Ohm\u2019s law. The amount of current, usually measured in milliamps, tells the PLC whether something is performing between on and off.<\/p>\n\n\n\n<p>These inputs could be for example;<\/p>\n\n\n\n<ul><li>in a Thermocouple or a Resistance Temperature Detector.<\/li><li>It could be a Pressure sensor<\/li><li>Or perhaps a Strain gauge<\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image\"><a href=\"https:\/\/theengineeringmindset.com\/wp-content\/uploads\/2021\/02\/6-2.png\"><img decoding=\"async\" src=\"https:\/\/theengineeringmindset.com\/wp-content\/uploads\/2021\/02\/6-2.png\" alt=\"\" class=\"wp-image-6152\"\/><\/a><figcaption>Analogue Inputs<\/figcaption><\/figure>\n\n\n\n<p>These voltage or currents are converted to a digital equivalent number that can be understood by the CPU. We will look at that a little later in this article.<\/p>\n\n\n\n<p>Input modules will perform 4 basic tasks;<\/p>\n\n\n\n<ul><li>They sense when a signal is received.<\/li><li>They convert the signal voltage into the correct signal for the CPU.<\/li><li>They isolate the PLC from fluctuations in the input voltage or current signal.<\/li><li>They send a \u2018corrected\u2019 signal to the CPU.<\/li><\/ul>\n\n\n\n<p><strong>The CPU or Central Processing Unit<\/strong>&nbsp;is the brains of the operation. It holds the programme, or software, that decides what outputs are required by applying rules to the input signals.<\/p>\n\n\n\n<p>The CPU typically consists of;<\/p>\n\n\n\n<ul><li><strong>A microprocessor,&nbsp;<\/strong>which does the work, based on the input value and the logic in the programme.<\/li><li><strong>A memory chip<\/strong>&nbsp;to store the program, this will also store the output history, any faults or alarms etc.<\/li><li><strong>Then we also have other integrated circuits<\/strong>, these can be for things like Modbus and LAN connections which allow us to remotely communicate with, reprogramme or monitor the device.<em><\/em><\/li><\/ul>\n\n\n\n<figure class=\"wp-block-image\"><a href=\"https:\/\/theengineeringmindset.com\/wp-content\/uploads\/2021\/02\/7-2.png\"><img decoding=\"async\" src=\"https:\/\/theengineeringmindset.com\/wp-content\/uploads\/2021\/02\/7-2.png\" alt=\"\" class=\"wp-image-6153\"\/><\/a><\/figure>\n\n\n\n<p><strong>Then there\u2019s the Output modules<\/strong>&nbsp;or Field Output Devices. This is providing the signal to the device we are controlling, for example a<\/p>\n\n\n\n<ul><li>&nbsp;A simple indicator light<\/li><li>A solenoid valve<\/li><li>A motor starter<\/li><li>A variable frequency drive<\/li><li>etc<\/li><\/ul>\n\n\n\n<p><strong>There are some other parts such as:<\/strong><\/p>\n\n\n\n<p>A battery to keep the PLC alive in the event of a power failure.<\/p>\n\n\n\n<p>There might be a small screen for a user interface, to allow some configuration.<\/p>\n\n\n\n<p>There will need to be a Time clock &amp; Calendar to operate a device at the correct time<\/p>\n\n\n\n<p>And there will also need to be a power supply to provide the low voltage used by the CPU as well as the Input and Output modules.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>First, we have the input modules or field sensors.&nbsp;These are the physical connections between the outside world and the PLC. These can be: Digital&nbsp;inputs, such as Simple On \u2013 Off switches Bi metallic temperature strips Presence or motion sensors Or even a Float switch These digital inputs can only provide information on whether something in [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[655],"tags":[],"_links":{"self":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/19982"}],"collection":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/comments?post=19982"}],"version-history":[{"count":0,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/19982\/revisions"}],"wp:attachment":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/media?parent=19982"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/categories?post=19982"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/tags?post=19982"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}