From the course: Learning PLC Ladder Logic: 2 Diving Deeper

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Example and solution 1: LIM

Example and solution 1: LIM - Ladder Logic Tutorial

From the course: Learning PLC Ladder Logic: 2 Diving Deeper

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Example and solution 1: LIM

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- [Instructor] Here is a simple example to show how the limit instruction works. Let's say that we have a machine application where an operator is allowed to enter the motor speed. The motor speed needs to be between zero and 1,750 RPM. If the value entered is between zero and 1,750 RPM, then the motor works. We are going to use a thumbwheel to enter the speed of the motor. The first thing we do is to use FRD instruction to take the values from the thumbwheel switch and save them in an integer value, N7:0. Then, in the second run, we add the limit instruction. The value of the low limit is zero, and the value for the high limit is 1,750. Now the value we're testing is the one we saved in N7:0, the thumbwheel value that the operator entered. If the value is within the limits, then the motor turns on, and I will use an LED to represent the motor operation. So here's the example in the software, and for the motor, I use the…

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