Programmable Controllers: Theory and Implementation

ntroduction to PLC Programming and Implementation—from relay logic to PLC logic(c)InputsOutputsL1 L2L1 L2PB14InputOutputPL3000020LS7001 021SOL3PS7002ProgramCoding022SOL4LS8SEL003004023024PL4SOL5LS9005025Start006026Reset00702714 c–ensure safety15 b–in series16 d–to shut down the system if there is a PLC failure17 A safety control relay is used to remove power from the I/O modules during a system error.When a malfunction occurs, the safety control relay will turn off, opening its SCR contact tostop the flow of power to the connected devices.18 false; most of the time a normally closed input device is programmed as normally open;however, the programming of the input will depend on its function in the program19 The normally closed PLC fault contacts are used to energize the PLC failure alarm. If the PLCfails, the PLC fault coil will not energize. Therefore, the normally open PLC fault contacts willnot close to provide power to the connected devices. Instead, the normally closed PLC faultcontacts will remain closed, sounding the PLC failure alarm.Industrial Text & Video Company www.industrialtext.com 1-800-752-839866