- Exclusive OR Gate(XOR-Gate)
- PLC Lab Exercise Logic Gates, PLC Ladder Logic Diagram Examples
- Logic Gates using PLC Programming [Explained with Ladder Diagram]
- Subscribe to RSS
- Digital Logic Functions
Exclusive OR Gate(XOR-Gate)Inverters and buffers exhaust the possibilities for single-input gate circuits. What more can be done with a single logic signal but to buffer it or invert it? To explore more logic gate possibilities, we must add more input terminals to the circuit s. Adding more input terminals to a logic gate increases the number of input state possibilities. As was mentioned previously in this chapter, a two input gate has four possibilities 00, 01, 10, and A three-input gate has eight possibilities,,and for input states. The number of possible input states is equal to two to the power of the number of inputs: This increase in the number of possible input states obviously allows for more complex gate behavior. Since so many combinations are possible with just a few input terminals, there are many different types of multiple-input gates, unlike single-input gates which can only be inverters or buffers. Each basic gate type will be presented in this section, showing its standard symbol, truth table, and practical operation. The actual TTL circuitry of these different gates will be explored in subsequent sections. In case you might have been wondering, AND gates are made with more than three inputs, but this is less common than the simple two-input variety. To symbolize this output signal inversion, the NAND gate symbol has a bubble on the output line. NOR gates, like all the other multiple-input gates seen thus far, can be manufactured with more than two inputs. In keeping with standard gate symbol convention, these inverted inputs are signified by bubbles. Its truth table, actually, is identical to a NOR gate:. Following the same pattern, a Negative-OR gate functions the same as an OR gate with all its inputs inverted. The Exclusive-OR gate, however, is something quite different. It is equivalent to an Exclusive-OR gate with an inverted output. In Partnership with Newark. Don't have an AAC account? Create one now. Forgot your password? Click here. Latest Projects Education. Textbook Multiple-input Gates. Home Textbook Vol. The Use of Logic Gate Inverters and buffers exhaust the possibilities for single-input gate circuits. Published under the terms and conditions of the Design Science License. You May Also Like. Log in to comment. Sign In Stay logged in Or sign in with. Continue to site.
PLC Lab Exercise Logic Gates, PLC Ladder Logic Diagram Examples
What we have is a simple OR logic function, implemented with nothing more than contacts and a lamp. We can mimic the AND logic function by wiring the two contacts in series instead of parallel: Now, the lamp energizes only if contact A and contact B are simultaneously actuated. A path exists for current from wire L 1 to the lamp wire 2 if and only if both switch contacts are closed. The logical inversion, or NOT, function can be performed on a contact input simply by using a normally-closed contact instead of a normally-open contact: Now, the lamp energizes if the contact is not actuated, and de-energizes when the contact is actuated. The lamp will be energized if either contact is unactuated. It will go out only if both contacts are actuated simultaneously. We can build combinational logic functions by grouping contacts in series-parallel arrangements, as well. The parallel connection between the two rungs at wire number 2 forms the equivalent of the OR gate, in allowing either rung 1 or rung 2 to energize the lamp. The common association between contacts is denoted by the label of the contact. There is no limit to how many contacts per switch can be represented in a ladder diagram, as each new contact on any switch or relay either normally-open or normally-closed used in the diagram is simply marked with the same label. This may be especially useful if you want to specifically designate which set of contacts on each switch or relay is being used for which part of a circuit. If you see a common label for multiple contacts, you know those contacts are all actuated by the same mechanism. If we wish to invert the output of any switch-generated logic function, we must use a relay with a normally-closed contact. When the coil of CR 1 symbolized with the pair of parentheses on the first rung is energized, the contact on the second rung opensthus de-energizing the lamp. From switch A to the coil of CR 1the logic function is noninverted. Applying this inversion strategy to one of our inverted-input functions created earlier, such as the OR-to-NAND, we can invert the output with a relay to create a noninverted function: From the switches to the coil of CR 1the logical function is that of a NAND gate. Don't have an AAC account? Create one now. Forgot your password? Click here. Latest Projects Education. Textbook Digital Logic Functions. Home Textbook Vol. Series contacts are equivalent to an AND gate. Normally-closed contacts are equivalent to a NOT gate inverter. Series contacts are logically equivalent to an AND gate. Normally closed N. A relay must be used to invert the output of a logic gate function, while simple normally-closed switch contacts are sufficient to represent inverted gate inputs. Published under the terms and conditions of the Design Science License. You May Also Like. Log in to comment. Sign In Stay logged in Or sign in with. Continue to site.
Logic Gates using PLC Programming [Explained with Ladder Diagram]
To understand programmable logic controllers PLCs and their applications, you must first understand the logic concepts behind them. The binary concept shows how physical quantities binary variables that can exist in one of two states can be represented as 1 or 0. Programmable logic controllers PLCs make decisions based on the results of these kinds of logical statements. These functions combine binary variables to form statements. There are many control situations requiring actions to be initiated when a certain combination of conditions is realized. Thus, for an automatic drilling machinethere might be the condition that the drill motor is to be activated when the limit switches are activated that indicate the presence of the workpiece and the drill position as being at the surface of the workpiece. Such a situation involves the AND logic functioncondition A and condition B having both to be realized for an output to occur. This section is a consideration of such logic functions. Figure 1a shows a situation where an output is not energized unless two, normally open, switches are both closed. We can think of this as representing a control system with two inputs A and B Figure 1b. Only when A and B are both on is there an output. Thus if we use 1 to indicate an on signal and 0 to represent an off signalthen for there to be a 1 output we must have A and B both 1. Such an operation is said to be controlled by a logic gate and the relationship between the inputs to a logic gate and the outputs is tabulated in a form known as a truth table. An example of an AND gate is an interlock control system for a machine tool so that it can only be operated when the safety guard is in position and the power switched on. The ladder diagram starts witha normally open set of contacts labeled input A, to represent switch A and in series with itanother normally open set of contacts labeled input B, to represent switch B. The line then terminates with O to represent the output. For there to be an output, both input A and input B have to occur, i. Figure 3a shows an electrical circuit where an output is energized when switch A or B, both normally open, are closed. This describes an OR logic gate Figure 3b in that input A or input B must be on for there to be an output. Figure The ladder diagram starts withnormally open contacts labeled input Ato represent switch A and in parallel with itnormally open contacts labeled input B, to represent switch B. An example of an OR gate control system is a conveyor belt transporting bottled products to packaging where a deflector plate is activated to deflect bottles into a reject bin if either the weight is not within certain tolerances or there is no cap on the bottle. Figure 5a shows an electrical circuit controlled by a switch that is normally closed. When there is an input to the switch, it opens and there is then no current in the circuit. This illustrates a NOT gate in that there is an output when there is no input and no output when there is an input Figure 5c. The gate is sometimes referred to as an inverter.
Subscribe to RSS
A logic gate takes Binary Input in the form of 0 or 1 and gives a Binary Output based on the Input provided; the output of the Logic Gate is also in the form of 0 or 1. In this software, we can write our ladder logic programs and we can also run simulations. I have a separate Tutorial on; how to use the WinProLadder Software and covered all the basics like for example how to start a new project, how to select a PLC model, how to use comments, how to write your first PLC program, and what is the best PLC for the beginners. So I highly recommend you should read this article and then you can resume from here. In this tutorial, we will cover the following gates. Some other most commonly used components and Tools:. Please Note: these are affiliate links. I may make a commission if you buy the components through these links. I would appreciate your support in this way! A NOT Gate is usually known as the inverter or Buffer is a logic gate that implements logical negation, in simple words the NOT Gate is used to convert 1 into 0 and similarly 0 into 1. The NOT Gate takes only 1 input and gives only one output. When the input is zero the output is 1, while when the input is 1 then the output is 0. As you can see in the pictures above when there is no input the output Y0 is high, while for high input we have low output at Y0. The output of the AND Gate is high when both the inputs are high. The output is low when any of the inputs are low. This can be clearly understood from the truth table given below. As you can see two normally open type contacts are used. When both the inputs are high the output Y0 is high. The output is low only when any of the inputs are low. So for the output to remain ON both the inputs should be high. If any of the inputs is low the output is high. The output is low only if both the inputs are high. The output is low when both the inputs are low. The OR Gate is implemented by connecting the inputs in parallel. As you can see in the pictures above, the output is off when both the inputs are low. While in the second picture you can see the output Y0 is high as the input2 is high. The output of the NOR Gate is high if both the inputs are low and the output is low if any of the inputs are high or both the inputs are high. As you can see when both the inputs are low the output is high and when any of the input is high then the output is low. The output of the XOR Gate is low for similar inputs while for the dissimilar inputs the output is high. So for similar inputs, the output is low, while for different inputs the output is high. As you can see for the similar inputs the output is low, while for the dissimilar inputs the output is high. You can see the X0 and X1 are used in series and they are also used in parallel. I hope that now you have an idea of how the logic gates are used in the PLC Ladder logic Programming. Let me know in the comment the output of the XNOR gate. You will get a notification email, each time I upload a new article. If you have any question let me know in a comment. Table of Contents. Recommended For You. Leave a Reply Cancel reply.