1. Direct and Indirect Control
Module 2
Direct and Indirect
Control

2. Module Objectives
1- Configure and connect the electrically actuated directional control valves (solenoid valves). 2- Configure the direct control in electro-pneumatics. 3- Configure the indirect control in electro-pneumatics. 4- Identify the advantages and disadvantages of direct and indirect control techniques. 5- Simulate and construct simple electric circuits

3. Module Contents
1. Solenoid valves 2. Types of solenoid valves 3. Direct control in electro-pneumatics 4. Advantages of direct control 5. Disadvantages of direct control 6. Practical task 1 7. Practical task 2 8. Indirect control in electro-pneumatics 9. Advantages of direct control 10. Disadvantages of direct control 11. Practical task 3

4. Electrically-actuated DCV - Solenoid valves
Forms of energies used to operate electro-pneumatic control system are:
Electrical energy.
Compressed air energy
Electrically actuated (DCVs) are switched with the aid of an electric coil that is called a solenoid.
The electric coil attracts or repels the valve spool

5. Operation
Activated
Not Activated

6. Solenoid valves groups
Single solenoid valve
with a spring return
Double solenoid valves
keeps and maintains the last switched position even when no current flows through the solenoid.
Memory Valve

7. Direct control in electro-pneumatics
It is the control of an electro-pneumatic valve without using intermediate components such as a relay, a contactor or an industrial computer (PLC).
Advantages of direct control
Simple and easy
Cheap.
Disadvantages of direct control
Remote control is not possible.
Switching more than one valve at a time is not possible.
Latching is not possible.
Design improvement is not flexible.

8. Direct control in electro-pneumatics
It is the control of an electro-pneumatic valve without using intermediate components such as a relay, a contactor or an industrial computer (PLC). (See the figure)

9. Practical Task 1
Direct control of a double acting cylinder using 5/2 DCV, single solenoid.
Objectives:
to be familiar with:
5/2 DCV, single solenoid, with spring return.
Electro-pneumatic equipment.

10. Background
A direct control circuit is used to control a 5/2 DCV single solenoid using a push button switch.
Activating the pushbutton will energize the coil (solenoid) which in turn will actuate (operate) the valve.

11. Solution to Practical Task 1
Required components
A double–acting cylinder
A 5/2 way valve, single solenoid
A power supply
A push button switches

12. Practical Task 2 Opening/closing the flow in a pipeline
The double acting cylinder (1A) in the Figure is used to open and close the main valve in a pipeline. Draw an electro-pneumatic circuit to control the movement of cylinder (1A).

13. Solution-1 to Practical Task 2 with a double acting cylinder

14. Solution-2 to Practical Task 2 with a double acting cylinder
Required components with a double acting cylinder:
Double – acting cylinder
5/2 way valve, double solenoid
Power supply
Switches

15. Class work (1)
3. Draw a pneumatic and an electric circuit to control a double solenoid valve directly, by using a normally closed detent switch.

16. Practical Task 3
Direct control of a double acting cylinder by using 5/2 DCV, double solenoid
Objectives:
to be familiar with:
5/2 DCV, double solenoid.
Electro-pneumatic components.
Electric circuits

17. Practical Task 3 Diverting machine
The parts used in the diverting machine are to be moved from one conveyor track to another. By pressing a pushbutton switch the frame of the diverting machine is pushed forward. The part is moved over and transported onwards in the opposite direction. By pressing another pushbutton switch the frame is returned to its start position as shown below.

18. Solution to Practical Task 3

19. Indirect control in electro pneumatics
Indirect control is the control of an electro-pneumatic valve using intermediate components such as relays, contactors or programmable logic controllers (PLC).

20. Advantages of indirect control systems
Remote control is possible
Switching more than one valve at a time is possible
Latching is possible.
Flexible design improvement and development.
Incorporating logic operating conditions (OR, AND conditions)

21. Disadvantages of indirect control
Complicated
More wiring
More cost involved

22. Practical Task 3 (Bulk material)
Problem description:
Bulk material is to be emptied from a hopper as shown in the Fig. By pressing a pushbutton switch, the hopper is opened and the bulk material is emptied out. By pressing another pushbutton switch the hopper is closed again.
Hint: The controlling circuit should contain relays for the indirect control

23. Solution to Practical 3

24. Solution to Practical 3

25. Solution to Practical 3

26. Homework 2

27. Homework 2 Solution 1

28. Homework 2 Solution 1

29. HW 2 Solution 2

30. HW 2 Solution 2

31. End of Module 2