The aim of this assignment is to design and implement a digital logic based controller for a water storage tank in a chemical plant.

The skills you demonstrate in this assessment are important because you will  apply the principles of digital logic to the design of a simple circuit and use standard interfacing protocols to connect circuitry to a computer system

Task Description

Using the knowledge you have gathered in the teaching and laboratory sessions, you are required to implement a digital logic based controller for a water storage tank in a chemical plant (shown in Figure 1). The purpose of the controller is to maintain the level of the storage tank using the inlet and outlet valves, and to maintain the temperature of the water in the storage tank within certain limits.

The basic operation of the system is:

1. The inlet valve should allow water to flow into the tank until the fluid level high sensor (LH) is activated by being immersed in the water. When this sensor is activated, the inlet valve (VI) should close.
2. The outlet valve (VO) should remain open all the time the fluid level low sensor (LL) is activated (again, this sensor is activated by being immersed in the water) and the water is at the correct temperature.
3. The control system has to maintain the temperature by turning on a heating element (H) when the temperature is too low (i.e. the fluid too cold sensor (TL) is activated). This heating element should be off at all other times.
4. There is also an indicator alarm (A) for when either the sensors fail or the water gets too hot.

Table 1 provides a truth-table linking these inputs and outputs.

You are required to design a circuit for the control system using NI Multisim (use an NI ELVIS II design so that it can be interface with NI ELVIS II board). You are also required to test this design practically using NI ELVIS II board. Your PC Multisim design should interface with the NI ELVIS II using the high speed USB bus interface.

You should also write a brief report detailing the incremental development of this system (e.g. the development of the inlet valve logic / the development of the outlet valve logic etc.).

You will need to perform these tasks:

Task 1. Logic simplification of the truth table in Table 1 using Boolean algebra and

Karnaugh Map. This allows creating the control system using minimum number of

the gates as possible making it more efficient. Details of this simplification should be

included in your report.

Task 2. NAND or NOR conversion of your minimized circuit from step 1 so that when

circuit uses only either NAND gate or NOR gate. You will have to use DeMorgan’s

law for this. Details of this should be included in the report as well.

Task 3. Construct the circuit for step 1 and step 2 using Multisim (attach the Multisim code file along with your report in the zip file to be submitted via Moodle).

Task 4. Construct the circuit for step 1 and step 2 using ELVIS II board (Demonstrate the circuit during the lab time to the tutor as evidence and include photo of the circuit in your report in appendix).

Task 5. Make sure outputs are same for step 1 and 2 verified by both step 3 and 4, detail of this should be included in the report.

Deliverable and marking scheme:

The investigation should produce the following deliverables. Marks will be allocated for:

1. Digital logic control circuit of inlet valve control.
2. Digital logic control circuit for outlet valve control.
3. Digital logic control circuit for heating element control.
4. Digital logic control circuit for alarm control.
5. Integrated digital logic controller for the whole system on both Multisim and NI ELVIS II board.

Mac 8 Slides including appendix

Report Content

You are required to submit an individual report for this assessment.

The report should describe the design process for constructing the digital logic control system. This should include details of the Boolean logic simplification for each of the controller elements from the supplied truth table and NAND/NOR equivalent circuit. Your report must also follow the criteria proved in the report structure and style.

Report Structure and Style