Ladder logic program examples lamp sequence

#LADDER LOGIC PROGRAM EXAMPLES LAMP SEQUENCE CODE#
#LADDER LOGIC PROGRAM EXAMPLES LAMP SEQUENCE SERIES#

The SeqControl is a CONTROL based instruction which takes care of the backend functions of the instructions. The SeqSource is the current state of the instruction and will transfer the array element from SeqArr where x is equal to the current step of the sequence. The functionality of this element is exactly the same as in the Masked Equal Instruction.

The SeqMask is a binary mask which will determine which bits need to be examined by the instruction. For example, if the first array specifies elements 3 and 4 to be energized, this translates into bits 3 and 4 of the first element of this array to be set. Each element of this array will define which inputs need to be energized in order to transition into the next step of the sequence. The SQI has several elements: SeqArr, SeqMask, SeqSource & SeqControl. Similarly, the SQO will be responsible for setting certain outputs based on the step the sequencer is in.

#LADDER LOGIC PROGRAM EXAMPLES LAMP SEQUENCE SERIES#

Through a series of matrices, the instruction will monitor the inputs at every step.

As mentioned above, the SQI is responsible for checking the inputs.

#LADDER LOGIC PROGRAM EXAMPLES LAMP SEQUENCE CODE#

They give the programmer a simple way to define the number of steps the sequencer needs to go through, which inputs & outputs need to be energized and provide a clear path to modifying current steps in order to accommodate new code or scaling.ДЄlthough this may seem like the perfect solution, it takes a little bit of practice in order to understand the functionality of SQI and SQO instructions. These instructions standardize & simplify the creation of the logic discussed above. The solution is to use the pre-defined RSLogix / Studio 500 & 5000 Instructions SQI and SQO sequencer input and sequencer output respectively. It works in theory but isnвЂ™t designed to scale. The flaws of the MOV Instruction as a sequencer become apparent as the application grows, changes need to be made and the application is passed down to a different party. The example above illustrates the way the sequencer should work, but not the proper implementation. Sequencer Implementation through SQI & SQO Instructions

The process is repeated until there arenвЂ™t any steps or the sequence is reset.

Once the actions have been completed, the next step is initiated.

An EQU Instruction is used to compare the value to a constant & allow certain actions to be carried out accordingly.

A MOV Instruction is used to change the step of the sequence by writing a specific value into the integer created above.

An integer is created & will be used to store the current step of the sequence.

Although this technique isnвЂ™t advised for larger applications hereвЂ™s an example of how this works: PLC Programmers have gotten used to implementing a sequencer through the use of MOV Instructions as mentioned above. As you go beyond this limit, the sequencer will be the preferred method of choice. A general rule of thumb is that if you have a process with 3 steps or less, you may implement a simple routine which goes through a series of MOV Instructions instead of a sequencer. As you develop PLC based applications, you will develop an intuition on where to use sequencers. Lastly, the step logic is what will control whatвЂ™s required to transition from one step to another and which outputs need to be set in a specific step.ДЄ sequencer will work best in applications which are defined by multiple steps which are dependant on each other. The outputs are used to identify what needs to be enabled at each step of the sequence.

The inputs are used to determine whatвЂ™s currently energized and how it enables the sequencer. The Sequencer Implementation StrategyДЄt the core, the sequencer is built from three components: Inputs, Outputs & Step Logic. In this tutorial, we will be going over the use cases of a sequencer, how the SQI and SQO instructions are setup as well as a practical example of a sequencer. Although the squencer isnвЂ™t something youвЂ™d expect to use on a regular basis, itвЂ™s an advanced technique which shines in specific applications. ItвЂ™s a technique which utilizes SQI and SQO instructions in order to create a sequence of events which is based on specific steps & allows the PLC to follow a prescribed sequence of events. Programming a Sequencer in Ladder Logic on a PLC is an advanced skill.

Ladder logic program examples lamp sequence