Caution_PL <Local:2:O.Data.4> Caution_PL Sensor_3 <Local:1:I.Data.3> ... Ladder logic Sensor_2 <Local:1:I.Data.2> FBD equivalent BAND_01 BAND Boolean And 0 0 In1 In2 Out In3 Sensor_1 <Local:1:I.Data.1> Sensor_1 Output Caution_PL Sensor_2 0 Sensor_3 0 L1 Inputs Sensor_1 Sensor_2 Sensor_3 Figure 15-106 Comparison between ladder logic and the FBD equivalent for a three-input AND ladder logic rung. <Local:2:O.Data.4> SOL_1 SOL_1 Ladder logic <Local:1:I.Data.3> <Local:1:I.Data.4> FBD equivalent ... BOR_01 BOR Boolean Or Sw_1 Sw_2 SOL_1 0 0 Sw_1 Out In1 In2 Sw_2 0 Inputs L1 Sw_1 Sw_2 L2 Output Figure 15-107 Comparison between ladder logic and the FBD equivalent for a two-input OR ladder logic rung. • Input In2 of the BOR block will be true only when all three of the sensor switches are closed. • Input In1 of the BOR block will be true only when the Temp_Sw is closed at the same time as the Press_Sw is open. • The BNOT function block executes similarly to an XIO ladder logic contact instruction. When In is 0, Out is 1 and vice versa. Figure 15-109 shows a comparison between ladder logic and the FBD equivalent for the motor start/stop L2 control circuit. The logic sequence for starting and stopping the motor can be summarized as follows: • When Motor_Start button is closed the BOR output will become true making the BAND output true. • Motor_Run output energizes the contactor coil, the contacts of which close to start the motor operating. • When the Motor_Start button is then opened the output of the BOR block remains true due to the 1 status of the feedback signal from the Motor_Run tag. Function Block Programming Part 6 389
Petruzella_ProgrammableLogicControllers__5e
To see the actual publication please follow the link above