Heating System Controller Project
The completion of this project is your take-home final for this
This project is an individual project. If you have any questions or need clarifications post them to the course discussion forum. You are to neither seek assistance from nor provide assistance to anyone. Your personal integrity will ensure that you adhere to these rules.
You are responsible for the design of a furnace system controller (FSC) in a home or small office. The physical description of the system is given below along with requirements defining the FSC operation.
This furnace uses oil as its fuel.
There is a master switch to turn the furnace on and off, and a sensor that indicates the difference between the desired temperature and the current temperature at the sensor. Processing the setting of the desired temperature is outside the scope of this controller.
A fuel valve controls the flow of fuel to the furnace. There are motors that drive a fan to provide combustion air, the fuel oil pump, and the circulating hot water pump.
There are binary sensors (true/false) for fan speed (normal RPM/low RPM), combustion flame (flame, no flame), and fuel flow (sufficient flow, low flow).
The controller has control outputs for the motors, fuel valve, and fuel ignitor. There are indicators for the fan, combustion, fuel, and circulating water.
- When the master switch is on, the controller shall turn the furnace on and off based on the temperature needs of the heated space.
- While the temperature difference sensor indicates a two-degree, or greater, positive difference, the controller will run the furnace.
- When the temperature difference sensor indicates a one-degree, or greater, negative difference, the controller will keep the furnace off.
- The controller shall safely start the furnace.
- Upon determining that the furnace should be started, the controller will start the combustion air fan motor and turn the fan indicator steady green.
- The controller shall open the fuel valve and turn on the fuel pump, if the fan speed sensor is true within 10 seconds.
- The controller shall spark the fuel ignitor, and turn the fuel indicator to steady green, when the fuel flow sensor turns true. The controller shall close the fuel valve, turn off the fuel pump, and start the fuel indicator flashing red, if the fuel flow sensor is not true within 5 seconds.
- The controller shall turn the combustion indicator steady green when the combustion flame sensor turns true.
- The controller shall close the fuel valve, turn off the fuel pump, and start the combustion indicator flashing red, if the combustion flame sensor does not turn true within two seconds.
- The controller shall turn on the circulating water pump, and turn the circulating water indicator steady green, after 30 seconds of combustion.
- The controller shall safely shutdown the furnace.
- Upon determining that the furnace should be shut off, the controller shall first turn off the fuel valve and turn off the fuel pump.
- When the fuel flow sensor goes false, the controller will turn the fuel indicator to steady red.
- When the combustion flame sensor goes false, the controller will turn the combustion indicator to steady red.
- Thirty seconds after the combustion flame sensor goes false, the controller shall turn off the combustion air fan motor, the circulating water pump, and shall set the fan and circulating water indicators to steady red.
- The controller shall monitor the furnace for safe operation while it is on.
- The controller will initiate a shutdown, and start the combustion indicator flashing red, if the combustion flame indicator turns false while fuel is flowing.
- The controller will initiate a shutdown, and start the fuel indicator flashing red, if the fuel flow sensor turns false while fuel is flowing.
- The controller will initiate a shutdown, and start the fan indicator flashing red, if the combustion fan sensor turns false.
The initial state of the system is assumed to be all motors off, fuel valve closed, master switch off, all indicators steady red.
There are a few other safety controllers on a typical furnace which will be outside the scope of this project.
The system boundary is the controller processor and its memory. All sensors, actuators and elements described in the Physical Description section above are outside the system boundary.
FSC Design Requirements
You are to do a behavioral analysis of this system to capture all of the requirements above. Create a statechart that describes this behavior. Provide a textual commentary that describes all the significant aspects of the statechart. You will most likely need to split the statechart into sections to make it readable and understandable.
For documentation of your design, you will submit a
single Word file that holds
the statechart and commentary.
Revision: $Revision: 1.3 $, $Date: 2008-02-11 05:40:51 $