MME 510 - Production Systems and Automation

EXPERIMENT 4: Silo simulator

I. Objectives

(a) Familiarization with the components used in an automated silo.

(b) Development of ladder logic diagrams for controlling the operation of a silo by a PLC.

II. Theory

Devices connected to the input and output modules of the PLC in silo exercise.

Logical sensors

Sensors allow a PLC to detect the state of a process. Logical sensors can only detect a state that is either true or false. Examples of physical phenomena that are typically detected are listed below.

• inductive proximity - is a metal object nearby?

• capacitive proximity - is a dielectric object nearby?

• optical presence - is an object breaking a light beam or reflecting light?

• mechanical contact - is an object touching a switch?

When a sensor detects a logical change it must signal that change to the PLC. This is typically done by switching a voltage or current on or off.

Solenoid

Output modules of PLCs are connected to a variety of on/off electrical devices. One major type is the electrical solenoid, illustrated in Fig. 1. A solenoid’s actuating plunger is held in position – in this case up – by a spring. When electricity is applied to its coil the plunger goes down. The plunger is connected to various types of mechanical devices. A common use is for the on/off control of flow valves such as the case in the silo simulator exercise.


Figure 1: Solenoid

III Experimental Work

From the Simulations Menu at the top of the screen, Select the Silo Simulation

Figure 2: Silo simulation

Exercise: Continuous mode of operation.

Completely design and de-bug a ladder control circuit which will automatically position and fill the boxes which are continuously sequenced along the conveyor. Ensure that the following details are also met:

  • The sequence can be stopped and re-started at any time using the panel mounted Stop and Start switches.
  • The RUN light will remain energized as long as the system is operating automatically.
  • The RUN light, Conveyor Motor and Solenoid will de-energize whenever the system is halted via the STOP switch.
  • The FILL light will be energized while the box is filling.
  • The FULL light will energize when the box is full and will remain that way until the box has moved clear of the prox-sensor.

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Lecturer: Dr. Sotiris L. Omirou