This Is What Happens When DECO Meets INCP & DECP! | How DECO REALLY Controls PLC Outputs ???

In this PLC tutorial, we will create a continuous Left-to-Right and Right-to-Left Running Lamp sequence using the DECO instruction as the main control instruction. The main focus of this video is the implementation of the DECO instruction, which controls the lamp output according to the numerical value stored in data register D0. The value of D0 is continuously changed by two instructions: INCP and DECP. At the beginning of the cycle, the INCP instruction becomes active and continuously increases the value of D0. As the value of D0 increases, the DECO instruction decodes the value and activates the corresponding output. The lamp sequence starts from Y0 and moves toward Y7. Therefore, the lamp appears to run from left to right across the output devices according to the decoded value of D0. A Timer T2 is used to control the speed of the running lamp. The timer setting is K1, corresponding to a timer interval of 0.1 seconds. This means that the value of D0 is increased step by step every 0.1 seconds, creating a visible running-light effect. When the value of D0 reaches 7, the INCP operation is stopped. The INCP instruction is disabled by the Normally Closed contact of the Load Pulse Rising M2 instruction. At this point, the control direction changes. The DECP instruction becomes active and starts decreasing the value of D0 step by step. When DECP is active, the DECO instruction uses the decreasing value of D0 to control the output sequence in the opposite direction. The lamp now runs from Y7 back toward Y0. In this sequence, Y7 is positioned on the left side and Y0 is positioned on the right side of the displayed lamp arrangement. Because D0 continuously decreases through the DECP instruction, the DECO output moves step by step from Y7 toward Y0. Timer T2 is also used during the DECP operation to control the movement speed. The timer remains set to K1, providing a 0.1-second interval between each change of the D0 value. When D0 reaches 0, the DECP operation is stopped. The DECP instruction is disabled by the Normally Closed contact of the Load Pulse Rising M1 instruction. After D0 reaches 0, the control sequence returns to the beginning. The INCP instruction becomes active again, increasing D0 from 0 toward 7. The DECO instruction then drives the lamps in the opposite direction again. As a result, the complete sequence continuously repeats: Y0 → Y1 → Y2 → Y3 → Y4 → Y5 → Y6 → Y7 Then the direction reverses: Y7 → Y6 → Y5 → Y4 → Y3 → Y2 → Y1 → Y0 The cycle continues automatically as long as the running condition remains active. A STOP button is also included in the control system. When the STOP button is pressed, the running cycle is stopped and all lamp outputs are turned OFF. This project is a useful example for understanding how DECO, INCP, DECP, data registers, timers, rising-pulse logic, and PLC output control can be combined to create a dynamic running-lamp sequence. The same programming concept can be adapted to various industrial applications, such as machine status indicators, sequential signal displays, stack lights, production-line indicators, equipment operating sequences, diagnostic displays, and automated visual signaling systems. Understanding this type of sequence is also useful for PLC programmers who want to improve their skills in data-driven output control and sequential machine programming. If you are learning Mitsubishi PLC programming, pay close attention to the relationship between the D0 numerical value and the DECO output, because this is the key concept behind the entire running-lamp sequence. Keep watching the video to understand how the ladder logic works step by step and how the direction changes automatically using INCP and DECP. Continue learning, practicing, and exploring new PLC programming techniques to improve your automation skills and build more advanced industrial control systems. #mitsubishi #plc #lamp #programming #tutorial #youtube #automation #automationliker #electrical #engineering