Apr 28, 2018 The first project is working and has been since installed. I have used like products on both projects, this includes the Click PLC, the larger power supply, two RTD input cards and one 4-channel Analog input card. The second project has an additional 24 vac input card. I have not began to stress the 1300 ma power budget having only exhausted. Inputs LEDs will not turn on when an input is overidden. Be sure to turn override bits off before returning the PLC to service. What do I need to read a barcode input? Web configuration page, go to the Email Setup page, click 'Enable Authentication' and enter the username and password in the fields provided.
- PLC Programming
- PLC Architecture
- Rockwell Automation
The term PLC inputs refers to the devices and transducers which are entrusted with taking in information about the physical world to the PLC. Keep in mind that it also refers to the PLC hardware that connects to those devices, sensors and transducers. The PLC uses this input information to make decisions based upon its program whether to energize and de-energize the outputs controlled by the PLC. It very important to know about the different input types discussed below.
The two types of PLC inputs are commonly referred to DI and AI (Digital and Analog). Analog inputs are those like temperature and pressure which span over a range of values. Digital inputs are simply two states, like those of a switch position indicating as On or Off.
Analog Inputs include temperature sensors/transmitters, current sensors, voltage sensors and others that can convert a physical quantity to a electrical signal. These electrical signals used for PLC input are typically 4-20ma or 1-5vdc.
Digital Inputs include push-buttons, limit switches, relay contacts, proximity switches, photo sensors (On/Off), pressure switches and more. Digital inputs devices are available in both DC as well as AC and some are voltage independent such as a switch contact.
A less common PLC input is the High Speed Counter (HSC). It is very similar to the digital input type, but the hardware is capable of detecting rapid ON/OFF inputs. It is common that 10KHz or 10,000 on/off transitions per second are within the abilities of these input types. A photo optic eye counting parts on an high speed assembly line would be example of when a HSC module would be needed.
A HSC PLC input module may also have quadrature capable inputs. This would be used with an rotary encoder to sense speed and direction of a motor for instance.
Depending on the particular PLC, the different inputs discussed above will require a separate hardware module for each type. However mixed I/O (input/output) modules or cards are available and some smaller integrated PLC models have some I/O included.
PLC Digital Inputs have a LED indicator on the module itself for setup and troubleshooting. Simply, if the LED is ON the input is ON.
If the LED is ON and it should not be, then you need to look at your wiring, the input sensor position or adjustment, or the possibility that the input device may be defective.The same applies if the LED is OFF and you expect to to be ON, with the addition of checking input protecting fuses.
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PLC Analog Inputs generally don't have a display on the module (I know that Automation Direct's newest top of the line PLC does!) to aid in troubleshooting. In this case you are going to need your multimeter or other suitable measurement tool.
The PLC input module itself would generally would be considered the last step in troubleshooting the problem.
Now that you understand the differences and uses of Digital and Analog inputs, be aware that the PLC input hardware is part of a system made of several different components that comprise a PLC. These components consist of the CPU or the central processing unit, the input and output modules, memory and power supply.
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Posted by3 years ago
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Isolated vs Non-isolated IO
Hello PLC experts, I have some questions about isolated inputs and outputs. I've looked on other message boards and found some conflicting information so I was hoping someone here could straighten me out.
So for inputs I understand that in isolated there is two wires and a separate common for each channel, whereas in non-isolated power is jumpered and provided to all field devices and only one wire goes back to the channel on the card. I've read that this gives the non-isolated input a higher point density. What are the advantages of isolated though. ie, if you were building a plant and someone asked if isolated or non islated would be appropriate how would you decide.
Same question for outputs. I believe one advantage of non isolated digital outputs is that they can be used functionally as contacts for motor starter wiring, eliminating the need for an interposing relay. Are there any other pros and cons? Thanks for reading and I would appreciate if someone could add their input
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