Page 409 - Programmable Logic Controllers, Fifth Edition - Mobile version

Ladder logic
Temp_Sw Press_Sw Alarm
<Local:1:I.Data.1> <Local:1:I.Data.2> <Local:2:O.Data.4>

L1 Sensor_1 Sensor_2 Sensor_3
<Local:1:I.Data.3> <Local:1:I.Data.4> <Local:1:I.Data.5> L2
Inputs Output
Temp_Sw
FBD equivalent Alarm Alarm

BAND_01
Press_Sw 0 BAND ...
Temp_Sw
Boolean And
BNOT_01 0
Sensor_1 BNOT ... In1 Out
In2
Boolean Not
0 1 BOR_01
Press_Sw In Out
Sensor_2 BAND_02 BOR ...
BAND ... Boolean Or
0
Sensor_1 Boolean And In1 Out 0 Alarm
Sensor_3 0 In1 Out 0 In2
Sensor_2
In2
0
Sensor_3 In3
Figure 15-108 Comparison between ladder logic and the FBD equivalent for a combination of multiple inputs.

Ladder logic
Start button for Stop button for
motor motor Motor contactor coil
Motor_Start Motor_Stop Motor_Run
<Local:1:I.Data.3> <Local:1:I.Data.4> <Local:2:O.Data.4>

Motor contactor coil
Inputs Motor_Run
L1 <Local:2:O.Data.4>
Output L2
Motor_Start
Motor_Run C
Motor_Stop

FBD equivalent
Start
Stop button for
motor
1 BAND_01
Stop BOR_01 Motor_Stop BAND ...
BOR ... Boolean And Motor
Start button for 0 contactor coil
motor Boolean Or In1 Out Motor_Run
0 0
Motor_Start In1 Out In2
In2

Figure 15-109 Comparison between ladder logic and the FBD equivalent for a motor start/
stop control circuit.

390 Part 6 Function Block Programming

pet73842_ch15_333-394.indd 390 03/11/15 7:34 PM