PLC set and resetIn the PLC control system, the self-locking control can be implemented with the set command
1 SET instructionThe SET instruction is called a set instruction. Its function is to drive the coil to have a self-locking function and maintain the on state. In Fig. 1, when the moving contact X0 is closed, the SET command is executed to turn on the Y0 coil. After X0 is disconnected, the Y0 coil remains on. To de-energize the Y0 coil, the reset command RST must be used.
The operating elements of the set command are output relay Y, auxiliary relay M, and status relay S.
2 RST instructionThe RST instruction is called a reset instruction. Its function is to reset the coil. In Fig. 1, when the moving contact X1 is closed, the RST command is executed to reset the Y0 coil. After X1 is disconnected, the Y0 coil continues to remain open.
The operating elements of the reset command are the output relay Y, the auxiliary relay M, the state relay S, the integrated timer T, and the counter C. It also clears the word elements D, V, Z.