P1: Describe the selection criteria and a practical application for a unitary, a modular and a rack-mounted programmable controller.

Task 1. (Criteria: P1)

You have been asked to describe the selection criteria for 3 different PLC applications. To do this:

a. Identify 3 real PLCs and 3 specific applications (1 for each PLC) that may be suitable for the following:

• A unitary PLC in a building
• A modular PLC in a factory
• A rack-mounted PLC in a factory

b. Estimate the quantities and types I/O devices required for each system to work e.g. 5 off 24v digital proximity switches, etc.

c. Finally illustrate your PLC requirements on a block diagram to show that the I/O can all be connected to the selected PLC, which might mean that you show several I/O modules.

Checklist of evidence required: 1a an image or reference as evidence of the real PLCs. Typical applications include auto door, heating control and conveyor systems. 1b. The estimate of quantities and types of I/O’s for each application should be supported by reason why you think these required. (2-300 words).1c. the 3 PLC block diagrams should match the specific applications you identify in 1a. Multiple I/O’s of the same type can be drawn as 1 line e.g. 1 line for: 5 off 24v digital proximity switches.

Task 2. (Criteria: P2)

Explain, with the aid of diagrams and/or commercial examples for each point below, the architecture of a modern PLC system. Include in your answer reference to:

a) system hardware,

b) two software options (i.e. languages),

c) input / output interface including digital/analogue, range of voltage/current used,

d) field devices including examples popular devices

e) communication links including a commercial example.

Checklist of evidence required: T2 - 500 word written report with at least 5 appropriate diagrams / examples

Task 3. (Criteria: P3)

The application above illustrates a simple stirring application in a lemonade factory.

a) Use LOGO to design and build the above system, using function block or ladder logic, which will control the operation as follows:

• When the Start ‘push to make’ (not toggle) switch (I1) is pressed/released, and gets latched on (B1: RS latch), the start ‘fill’ pump (Q1) will be energized and the tank will start to fill.
• The pulses generated by flow meter 1 (B5: pulse generator) should be used to increment the counter (B6: Up/down). Tank level full is when the counter function on = 10 and tank low level is when counter off = 1. These values can be used as feedback to control the pumps (instead of the high/low level sensors shown above) and can be called the ‘tank high/low level count indicator’ (Q5 or use a flag M1)
• When the full liquid level in the tank is sensed by the tank high/low level count indicator (Q5), the fill pump will be shut-off and the FULL light (Q2) on the control panel is to be energized.
• When the tank is full, start the mixer (Q3) and run for 10 seconds (B8: off-delay timer).
• When the 10 seconds has expired, stop the mixer (Q3) and start ‘empty’ pump P3 (Q4).
• Pump 3 (Q4) will be required to run until the tank is empty.
• The pulses generated by flow meter 3 (B15) should be used to decrement the counter (B6: Up/down). Tank empty can be detected by the high/low level count indicator (Q5 or use a flag M1) to switch off the pump
• When the stop button (I2) is operated, the process must stop immediately (Q1, Q3, Q4).

b) Test your LOGO build and comment on your testing using LOGO simulation mode. This requires at least 3 print-screens of testing the system using the LOGO simulator below at the filling, mixing and emptying stages

c) Save your program and email/Dropbox a copy of your program along with your assessment

Guidance: Clearly snip/print-screen and explain your build and test work. Use input/output (I/Q) numbers shown. Function numbers (B) can be your own choice, and you are also likely to need some basic logic functions (e.g. And/Or/Not) for the various conditions given in 3a.

Checklist of evidence required: T3 – (Snip) Image of program layout and test evidence, and a copy of PLC LOGO program file