Temperature controller, Electrical Engineering

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This assignment concerns the planning of a software development. You are required to plan the software development for a typical microprocessor based, 4-channel temperature controller. You should assume the hardware has already been defined and planned.

Specification

Key Features

• A small LCD display, 4 lines, each of 32 characters

• A small keypad with 7 keys:

o select Commissioning mode

o select Programming mode

o select Run mode

o Inc - allows the user to increment a value

o Dec - allows the user to decrement a value

o Move right/up - allows the user to move right on a display line or up to the next display line

o Move left/down - allows the user to move left on a display line or down to the next display line

Inputs

• Temperature - analogue inputs, between 0 and 100 degrees Centigrade, 4 channels

• Keypad - digital levels, 7 bits

Outputs

• 4 voltage-free relay contacts, to switch 240V mains. The four relays are reed relays, one for each channel.

Operation

• Pressing any of the three mode keys enters the selected mode. Pressing the key again exits that mode and leaves the unit in aninactive state.

• In Commission mode, the user must be able to set the date and time (today's date).

• In Programming mode, the user must be able to set the time for which each channel relay operates if the measured temperature is less than the channel low temperature limit, or greater than the channel high level temperature limit.

• In Programming mode, the user must be able to set both a low and high level temperature limit for each of the system channels. If the channel temperature is less than the channel low limit, the channel relay contacts are closed. If the channel temperature is greater than the channel high level limit, the channel relay contacts are opened.

• When the user presses the Run key, the product enters the run mode if all the necessary channel data has been set. Pressing the

Run key a second time puts the unit into an inactive state.

• During Run mode the data for each channel is displayed and the user can scroll round the channel data using the Inc and Dec keys.

• In addition to three modes described, a Self Test mode is to be provided. Self Test is entered when power is applied with all three mode switches depressed.


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