Problem Identification Despite the growing popularity of the usage of air conditioners, electric ceiling fans are still widely in use all over country. Air conditioners, though providing users with the option of precision temperature regulation along with several other features, remain largely unaffordable to the majority of consumers. Ceiling fans, on the other hand, with their relatively lower price ranges, easy installation ability and simple control mechanism still remain the most popular domestic cooling appliances for user thermal comfort in tropical countries like Sri Lanka. Presently, conventional choke-styled fan regulators as well as the more expensive smooth dial regulators are available in the market. These give the user the option of setting fan speed as desired depending on ambient environmental status (temperature, humidity etc.) with the latter product affording greater speed variation as opposed to its’ counterpart. Perhaps the major problem with fan regulators currently in the Sri Lankan market is their inability to automatically regulate fan speed corresponding to changes in the external environment. This proves to be somewhat of an inconvenience to the user. One might often set the dial of the regulator to its’ maximum speed prior to going to bed with the room being warm and humid, and yet awake feeling too cold in the morning due to a significant drop in temperature. The opposite too, that of temperature rising at night, although not frequent, is a possibility. Furthermore, existing regulators have the additional disadvantage of not being energy efficient as they even continue to draw the same amount of power when the fan is operating at a slower speed. Preliminary survey for existing products indicated that similar products exist in foreign market for considerable higher prices while such products have not been introduced to Sri Lanka consumer market so far. To address the issues identified, we decided to int roduce a new design with automatic speed regulation in accordance with ambient temperature and low power consumption for an affordable price. Before moving on, we conducted a user survey to get confirmed whether there really is such a necessity for automatic temperature regulation for long and whether for new product has its marketability.
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Based on the data collected above, predominant needs appearing multiple times
across all listed categories were identified.
Out of major needs identified above, two significant needs have been accounting for
more than 50% of all needs. Those are,
Facility of remote control.
Automatic Remote Speed Control in according with ambient temperature.
Although Automatic speed control would satisfy the necessity of having remote
control and adding remote control increases the total cost, we decided to consider the facility
of remote control in conceptual design while having a thought of dropping that feature if itadds unnecessary complexity to the design. Then we developed the following design
specifications taking above mentioned user needs and technical issues in to consideration.
5%
23%
31%4%
3%
3%
3%
3%
25%
Major Needs Identified
Power Saving Mechanism
Automatic Control depending onRoom being too Warm/Cold
Interface to switch between auto and manual mode.*
Interface to set reference temperature (In auto mode) Interface to set fan speed (In manual mode)*
Continues variation of speed in accord ance with ambient temperature. †
* Even though the user survey doesn’t indicate any necessary for both auto and manual modes together there isan issue arises when manual control is necessary for some special cases. So we decided to add both auto andmanual mode to work in harmony.
† Even though user need survey does not indicate continues variation of speed in accordance with temperature,we added it as a hidden need as it makes consumer more comfortable and does not require extra cost.
To fulfil the above we came up with 2 different conceptual designs.
Conceptual Designs
Design 1
In auto mode of operation, the reference temperature value set by the user and
ambient temperature value read through the temperature sensor are fed into control unit. The
control unit calculates the error between two values and generates a signal accordingly and
passes it to voltage regulator. Voltage regulator regulates the power input to the fan in
accordance with the signal received from control unit.
In manual mode of operation, only the speed value set by the user is fed into control
unit and then the control unit generates a signal with respect to the error value between
received value and pre-defined reference value. This calculated value is fed into the voltage
regulator which regulates the power input to the fan in accordance with received signal.
Design 2
Temperature sensor and the user interface are located in a remote control. It sends the
values read through sensor and user interface to a receiver which is placed inside a gadget
which is attached to fan itself. All other functions are similar to the conceptual design 1
Employs a rectifier circuit and a voltage regulator circuit to convert normal AC to12V and 5V DC to feed control circuit and other peripheral circuits with.
Control Circuit
Employs a PIC16F877A microcontroller to calculate error between user input and
temperature sensor input and to generate a pulse accordingly.
1. Do you have an air conditioner at home (yes/no)?
2. Do you have a fan at home? (yes/no) if yesCeiling fan : .........................Table fan : .........................
3. At what time of the day do you mostly use your air conditioner/fan? (Morning / Afternoon / At Night)
4. What are the problems you face when using your fan?..............................................................................................................................................................................................................................................................................................................................................................................................................................
5. What improvement would you like to have included in your fan?..............................................................................................................................................................................................................................................................................................................................................................................................................................
6. If you had an air conditioner instead of a fan, you would (like it / would not like it / makeno difference)Reason : ..................................................................................................................................
7. How many units of electricity do you consume per montha. Less than 60b. Between 60 and 90c. Between 90 and 150d. Between 150 and 300e. Do not know
8. Are you concerned about the power consumption of the electric goods you purchase?