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**Logic Operations in Electro-Pneumatics**

Module 3 Logic Operations in Electro-Pneumatics

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Module Objectives 1- Explain the concept of logic operation (OR circuits). 2- Explain the concept of logic operation (AND circuits). 3- Construct the truth table for different logic operations. 4- Use the concept of logic operations (AND/OR circuits) in building simple control circuits according to the given application. 5- Describe the types and use of latching circuits. 6- Use latching in building simple control circuits according to the given application.

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**Module Contents 1. Logic operations-OR circuit**

2. Truth table of the OR circuit 3. Logic operations-AND circuit 4. Truth table of the AND circuit 5. Practical Task 1 6. Practical Task 2 7. Latching Circuits 8. Types of latching 9. Practical Task 3 10. References

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**Logic Operations They are used to produce the required**

movements by pneumatic cylinders under certain conditions. logic operations are: 1. OR circuits 2. AND circuits.

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**Logic operation - OR circuit**

The OR circuit has two inputs and a single output. The aim is to be able to extend the piston rod of a cylinder with two different input elements, pushbutton S1 and S2. The contacts of the pushbuttons S1 and S2 are arranged in parallel branches in the circuit diagram If at least one of the two pushbuttons is pressed, the solenoid valve switches to the actuated position and the piston rod advances.

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**Truth table of the OR circuit**

0: push buttons are not pressed and thus there is no input signal. 1: push button pressed and thus the input signal exists. Y1 is 0 means the solenoid valve is not activated Y1 is 1 means the solenoid valve is activated S1 S2 Y1 1

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**Logic operation - AND circuit**

The AND circuit has two inputs and a single output. The output of the AND circuit exists only when both inputs are existing.

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**Truth table of the AND circuit**

0: push buttons are not pressed and thus there is no input signal. 1: push button pressed and thus the input signal exists. Y1 is 0 means the solenoid valve is not activated Y1 is 1 means the solenoid valve is activated S1 S2 Y1 1

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**Practical Task 1 Operating a pneumatic press directly**

Problem description: The pneumatic press that is shown in the Figure has to be operated by two switches at the same time in order to protect the operator hands from any possible injury during the press operation. The press will be released automatically by a limit switch. However, another switch has to be provided to release the press in case of the limit switch malfunction.

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**Practical Task 1 Required components: Required procedures:**

1- Double acting cylinder 2- 5/2 DCV, double solenoid. 3- Power supply 4- Switch blocks Required procedures: 1. Draw the elector-pneumatic circuit using FluidSIM software 2. The speed of the forward and backward strokes are adjustable. 3. Test the circuit functions against any errors or mistakes. 4. Construct the circuit on the workstation 5. Write down your notes and observations.

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**Solution to Practical Task 1**

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**Solution to Practical Task 1**

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**Solution to Practical Task 1**

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**Practical Task 2 Operating a pneumatic press indirectly Objectives:**

1- Explain and use the AND connection practically to ensure a safe operation. 2- Explain and use the OR connection practically. 3- Explain the indirect (using electric relays) control circuit with AND/OR. 4- Be able to use the FluidSIM software as well as workstations. Problem description: The problem description for this task is the same as for the above task (task 1).

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**Practical Task 2 Required components: Required procedures:**

1- Double acting cylinder 2- 5/2 DCV, double solenoid 3- Power supply 4- Switch blocks 5- Relay blocks Required procedures: 1- Draw the elector-pneumatic circuit using the FluidSIM. 2- Test the circuit functions against any errors or mistakes. 3- Construct the circuit on the workstation. 4- Write down your notes and observations.

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**Solution to Practical Task 2**

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Class work

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Latching Circuits It is a process where the relay contacts remain on without keeping the relay coil energized. it is required sometimes to keep the circuit powered for a certain function even though a pushbutton switch is released to the open position.

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Way of operation When the “ON” pushbutton switch is actuated as shown in Fig.3.5.a, the relay coil is energized and thus the contact K1 closes. Even after the “ON” pushbutton switch is released the electric current continues to flow via contact K1 through the coil, and the relay remains in the actuated position. The “on” signal is stored. When the OFF pushbutton is pressed the current flow is interrupted and the relay becomes de-energized

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Types of latching 1- dominant ON. 2- dominant OFF

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1- dominant ON if the “ON” and “OFF” pushbuttons are both pressed at the same time, the relay coil is energized. That’s why the circuit in Figure is called a dominant ON latching circuit

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2- dominant OFF If both pushbuttons are pressed simultaneously: the relay coil is not energized. That’s why the circuit in Figure is called a dominant OFF latching circuit

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**Practical task 3 (Latching circuit)**

Problem description: Parts are to be pushed away from a multi-track gravity feed magazine into a clamping device as shown below. By pressing a pushbutton switch the parts are pushed out of the multi-track gravity feed magazine by a slide. After the slide has reached the forward end position it has to return to its start position. Hint: A relay with latching function is to be used for signal storage.

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**Practical task 3 (Latching circuit)**

Required components: 1- Double acting cylinder 2- 5/2 DCV, single solenoid 3- Power supply 4- Switches block 5- Relay block 6- Limit switch

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