Programmable Controllers: Theory and Implementation

Introduction to PLC Programming and Implementation—from relay logic to PLC logic29 The PLC implementation of the large relay circuit in Figure 11 should include anormally open PLC fault contact and use internals to trap the timers. The PLC systemhas capacity for 512 I/O (000 to 777 octal). Inputs should start at address 000 8 andoutputs should start at address 030 8 . Internals should have addresses 1000–1777,MCRs should have addresses 2000–2037, and timers should have addresses2040–2137. Using this large relay circuit:(a) indicate the portions to be left hardwired(b) assign the I/O addresses(c) assign the internal addresses(d) draw the I/O connection diagramCoolantPump MotorHydraulicPump MotorSpindleMotorM3M2M1OLsOLsOLsDisconnectSwichFusesM3M2M1L1L2F1StopStartPLC FaultContact 1M2OLsM2 M3M3OLsSCRSCR123Setup/RunRunCR1CR2UpLS1CR1PL1M1CR1CR2OLs456EnableMCRPL2MasterControlRelayMaster ON(continued on next page)Figure 11. Large relay circuit.Industrial Text & Video Company www.industrialtext.com 1-800-752-839862