DUE FRI, 02/17/17 (By Noon)

Industrial Pneumatics Name ______DUE FRI, 02/17/17 (by noon) Lab 6: Logical Combinations You have studied basic logic including creating truth tables. Since electrical circuits can control Fig. 1 multiple outputs, truth tables can show logic for more than one output. INPUTS OUTPUTS In Fig. 1, A and B are inputs and X and Y are outputs. Output X A B X Y is only true when A is true and B is false. Y is true only when A 0 0 0 0 and B are both true. Make sure you understand this. 0 1 0 0 1 0 1 0 To create a ladder diagram from a truth table follow these steps: 1 1 0 1 1. Find the rows whose outputs are 1s (ones). (Disregard outputs that are 0s (zeros). 2. Translate those rows to logical statements. 3. Translate inputs that are 1s to a normally open switch or contact, and inputs that are zeros to normally closed switches or contacts.

For the truth table in Fig. 1, consider only the bottom two rows. The logical statements would be: Row 3:If A AND NOT B then X. Row 4: If A AND B then Y.

The fact that there are two “true” truth-table rows and two logical statements tells us that there will be two rows in the ladder diagram. We can then develop the ladder logic as shown in Fig. 2. +

IF A AND NOT B THEN X

IF A AND B THEN Y

Fig. 2 Notice that the ladder diagram in Fig 2. uses normally open and normally closed (relay) contacts. The diagram could have been designed using normally open and normally closed pushbuttons, but using relay contacts provides increased flexibility in circuit design.

1 Bulk Material Mixing System

Problem Description The control for a bulk material mixing system consists of two pushbuttons. The first pushbutton (PB1) is used to select the desired dispensing silo (Silo A or Silo B).

Once the appropriate silo has been selected, pressing the second pushbutton (PB2) opens the silo, dispensing the product.

Positional Diagram

Note: Use relay contacts to provide logic and single solenoid 5/2 DCVs to control the cylinders. NOTE: The cylinders should start in the extended position and retract to allow flow from the silo. Rapid closing of the silos is required.

Equipment List (2) Double-acting cylinders (2) Single-solenoid, spring return 5/2-way DCVs (2) Quick exhaust valves (2) Pushbuttons (2) Control relays

2 Truth Table Complete the truth table for the problem in this exercise

PB1 PB2 Output Output Silo A Silo B

Write out the logical statements from the truth table in “if-then” form. Include only the statements where an output will be generated.

1. ______

2. ______

In the space below draw the pneumatic circuit diagram and a ladder diagram to solve the problem in this exercise. Use a detent pushbutton to select the silo and a N.O. pushbutton to dispense the product. Use the pushbuttons only to energize the relay coils and develop the logic (above) using the contacts controlled by the coils. The contacts, in turn, drive solenoids controlling the dispensing valves. LABEL EVERYTHING. Pneumatic Circuit Diagram Ladder Logic Diagram

Transfer your sketches to FluidSim & verify correct operation. LABEL EVERYTHING. Show your sketches and FluidSim circuit to the lab instructor. Initials ______Construct the circuit and prove its operation. Initials ______

3 Review Questions For the following logical statements:

If not A and not B then X If A and B then Y. If A and not B then Z If A or B then Z A. Complete the truth table A B X Y Z

B. Sketch out a ladder diagram. Use pushbuttons as inputs, A & B. The pushbuttons energize relay coils. The coils control their respective contacts. The contacts drive solenoids, X, Y & Z. NOTE: Just like in the lab, the logic should be developed via the relay contacts, NOT the pushbuttons.