Page 728 - Mechatronics with Experiments

714 MECHATRONICS
Start
1 Auto Run
1001 1001 1002 0032 Lift doors
2
Stop
0032 0001
1002 3 Begin Cycle
Belt motor
Doors open 1006 0028 0031 M1
4
0002
1003
0031 0001
5
450° Temp
1006
1004 Heater
6
0003
500° Temp
0031 1003 0032 0002
1005 7
1006
Presence sensor
8 Heat Treat
1006 1006 0031 0030
9 Heat ON
1004 1003 0028 0029
10
1005 0029
11
0032 0029 420 0003
12 Heat Timer
T 1 0
1004 0028
13 4001
0030
14
0028 0031

FIGURE 9.14: Ladder logic diagram for the heater–conveyor control using a PLC.

9.6 PROBLEMS

1. Consider the temperature control system shown in Figure 9.10. Specify the necessary PLC
hardware (PLC plus the required I/O modules). Design a ladder logic diagram so that the PLC
controls the temperature using the temperature sensor as a feedback signal and the proportional fuel
valve as the controlled actuator. The logic should include input switches to start and stop the control
system as well as display status information to the operator.

2. Consider the speed control system shown in Figure 9.11. The objective is to run the conveyor 1
at a programmable speed where that value is entered by the operator via an operator interface device.
The conveyor 2 is suppose to run as if it is mechanically geared to conveyor 1 and the gear ratio is also
programmable by the operator. Specify the necessary PLC hardware and design the LLD program.
3. Consider the position control system shown in Figure 9.12. Our goal is that when the operator
pushes the “Start” button, the automatic cycle of the positioning table starts. When the “Stop” button
is pushed, the table is supposed to stop to a predefined home position. When the start button is pushed,
the motor is to move in a direction to seek the “home” sensor. If it reaches one of the limit switches
before reaching the home sensor, then it must reverse direction, go past the home sensor, stop, and
come back to turn ON the home sensor from a predefined direction. Then stop and establish a “home”
reference. After that, the motor is suppose to make incremental forward and reverse motions, that is