DESC:FIELD OF INVENTION
The present invention relates to a speed control system for a cost effective brushless DC (BLDC) motor based energy efficient ceiling fan, which uses capacitive step-type fan regulator. Further, the present invention relates to speed control system for a BLDC motor based energy efficient ceiling fan, which controls fan speed based on difference in rectified voltages during power-on and also when the fan regulator position changes in real time.
BACKGROUND OF INVENTION
In the prior art the speed control for the BLDC motor based ceiling fan is achieved by an infrared (IR) remote control whose IR receiver is embedded in the motor. The embedded system decodes the information and changes the speed of the fan according to the command from the remote control. This is akin to the operation in several remote-controlled household appliances such as TV, music system etc. However, in public places in general and hospitals, large offices, schools and colleges in particular, remote control can be inconvenient for obvious reasons. A wall mounted fan regulator is more convenient in such places.
OBJECTS OF INVENTION
The primary object of the present invention is to use a low cost and wall mountable capacitive step-type fan regulator (4 positions or 5 positions) to control the speed of the fan, instead of a remote control.
The present invention solves the problem by incorporating an electronic system, comprising of a capacitor, a TRIAC (AC switch), a voltage divider and a programmed microcontroller with firmware, which works with a wall mounted capacitive step-type fan regulator.
In each step the capacitive step-type fan regulator interposes different impedance between the mains supply and the fan.
During power-on, the impedance value in the fan regulator is interpreted and then processed by the programmed microcontroller and the corresponding fan speed is set.
In the present invention the desired speed can be controlled by changing the fan regulator knob (switch S1) of the capacitive step-type fan regulator to the corresponding position. The switch S1 in the fan regulator should be of break-before-make type. The detection of a change in position and determination of the fan regulator step position is based on the monitoring of the rectified voltage using the firmware programmed in the microcontroller.
Whenever the user changes the fan regulator knob from one position to another there is a change in the rectified voltage due to a break in the mains supply and also there is a change in the impedance. The change in impedance value is then interpreted and processed by the programmed microcontroller and the corresponding fan speed is set.
SUMMARY OF INVENTION
Thus according to the embodiment of the present invention there is provided a speed control system for a BLDC motor based ceiling fan using wall mounted capacitive step-type fan regulator comprises of at least one Capacitive step-type fan regulator; at least one Programmed microcontroller; at least one TRIAC (AC switch); at least one Capacitor; and at least one Voltage divider,
It is another aspect of the present invention, wherein, the Capacitive step-type fan regulator is fitted on the wall of the building where the ceiling fan is fitted,
It is another aspect of the present invention, wherein, the Capacitive step-type fan regulator consists of a switch and capacitors,
It is another aspect of the present invention, wherein, the switch is break-before-make type switch,
It is another aspect of the present invention, wherein, the programmed microcontroller with the firmware algorithm sets the corresponding fan speed, when the user changes the capacitive step-type fan regulator knob position from one position to another, by detecting the capacitive step-type fan regulator knob position change and determining the capacitive step-type fan regulator step position.
It is another aspect of the present invention, wherein, the voltage divider consists of the top resistor and the bottom resistor connected in series, with the input voltage applied across the resistor pair and the divided down rectified voltage is emerging from the connection between the top resistor and the bottom resistor,
It is another aspect of the present invention, wherein, the programmed microcontroller with the firmware algorithm monitors the divided down rectified voltage and detects the capacitive step-type fan regulator knob position change, when the divided down rectified voltage goes less than the value set in the programmed microcontroller.
It is another aspect of the present invention, wherein, the programmed microcontroller with the firmware algorithm compares the average peak value of the rectified voltage with the capacitor connected and the average peak value of the rectified voltage without the capacitor connected by turning ON/OFF the TRIAC (AC switch) respectively to determine the step position of the capacitive step-type fan regulator.
It is another aspect of the present invention, wherein, the programmed microcontroller with the firmware algorithm sets the corresponding fan speed during power-on, by determining the step position of the capacitive step-type fan regulator.
It is another aspect of the present invention, wherein difference in value between the average peak of the rectified voltage with the capacitor connected and without the capacitor connected, will change depending on the change in the impedance value of capacitive step-type fan regulator, which in turn corresponds to the capacitive step-type fan regulator step position.
It is another aspect of the present invention, wherein the capacitive step-type fan regulator is four-step capacitive fan regulator (4 positions).
It is another aspect of the present invention, wherein the capacitive step-type fan regulator is five-step capacitive fan regulator (5 positions).

BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1: illustrates a Sensorless BLDC motor based ceiling fan connected with external capacitive step-type fan regulator according to the present invention.
Figure 2: illustrates the circuit diagram of a Sensorless BLDC motor drive system for a ceiling fan with external capacitive step-type fan regulator according to the present invention.
Figure 3 is a flowchart illustrating detection of the change in fan regulator knob position according to the present invention.
Figure 4 is a flowchart illustrating the determination of the fan regulator step position according to the present invention.
Figure 5 is a screenshot illustrating the divided down rectified voltage waveform, which is captured during the detection of the change in fan regulator knob position, according to the present invention.
Figure 6 is a screenshot illustrating the divided down rectified voltage waveform with the capacitor connected and without the capacitor connected, which is captured during the determination of the fan regulator step position, according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES
Figures 1 to 6 of the drawings, illustrate the speed control system for a BLDC motor based ceiling fan using wall mounted capacitive step-type fan regulator (100) according to the present invention. As shown in figure 2, an external capacitive step-type fan regulator (100) is connected to an electronic controller, comprising of a capacitor (103), a TRIAC (AC switch) (102), a voltage divider (104) comprising of the top resistor (104a) and the bottom resistor (104b) and a programmed microcontroller (106) with firmware. The capacitive step-type fan regulator (100) is normally fitted on the wall of the room where the ceiling fan is fitted. The capacitive step-type fan regulator (100) comprises of a break-before-make type switch (S1) and capacitors. It is one of the aspects of the present invention, wherein the capacitive step-type fan regulator (100) is a four-step capacitive fan regulator, in which the fan speed is set to 1st, 2nd, 3rd and 4th to control the speed of the fan in 4steps. It is another aspect of the present invention, wherein the capacitive step-type fan regulator (100) is a five-step capacitive fan regulator, in which the fan speed is set to 1st, 2nd, 3rd, 4th and 5th to control the speed of the fan in 5 steps.
In the present invention, during power-on, the impedance value in the capacitive step-type fan regulator (100) is interpreted and then processed by the programmed microcontroller (106) and the corresponding fan speed is set.
In the present invention the desired speed can be controlled by changing the knob of the capacitive step-type fan regulator (100) to the corresponding position. The capacitive step-type fan regulator (100) according to the present invention employs the switch (S1) which is of break-before-make type. Whenever the user changes the capacitive step-type fan regulator (100) knob from one position to another there is a change in the rectified voltage (105) due to a break in the mains supply and also there is a change in the impedance (Zc). The change in impedance is detected by the programmed microcontroller (106) by monitoring the divided down rectified voltage (105) using the analog to digital converter of the programmed microcontroller (106). This change in impedance (Zc) is then interpreted and processed by the firmware in the programmed microcontroller (106) which is programmed appropriately in order to run the fan at the required speed.
The programmed microcontroller (106) monitors the divided down rectified voltage (105) for
1) Detection of the capacitive step-type fan regulator (100) knob position change and
2) Determination of the capacitive step-type fan regulator (100) step position.
The voltage divider (104) comprises of the top resistor (104a) and the bottom resistor (104b) that are connected in series and the input voltage is applied across them and the divided down rectified voltage (105) is emerging from the connection between the top (104a) and bottom (104b) resistors. When the user changes the capacitive step-type fan regulator (100) knob position, there will be a change in the divided down rectified voltage (105) due to a break in the mains supply. As shown in figure 1, since the switch (S1) in the capacitive step-type fan regulator (100) is a break-before-make type switch, there is a break in the mains supply and then a new path connection is established.
Figure 3 illustrates the logic implemented in the firmware to detect this change in the divided down rectified voltage (105). The rectified voltage (105) is converted to a digital number by using the analog to digital converter in the programmed microcontroller (106). The firmware algorithm uses this digital word and continuously monitors the divided down rectified voltage (105). Whenever the divided down rectified voltage (105) is within the set value programmed in the programmed microcontroller (106), for example which is between 0.01 to 0.3V, then the programmed microcontroller (106) detects that there is a change in the capacitive step-type fan regulator (100) position. The oscilloscope screen shot of the divided down rectified voltage waveform captured during the detection of capacitive step-type fan regulator (100) knob position change from one position to another is shown in figure 5.
Once the programmed microcontroller (106) detects that the capacitive step-type fan regulator (100) position has changed, it then implements the logic illustrated in figure 4 to determine the capacitive step-type fan regulator (100) step position. To find the capacitive step-type fan regulator (100) step position, the firmware logic in the programmed microcontroller (106) switches OFF the motor and measures the peak of the divided down rectified voltage (105) without the capacitor (103) connected, that is with the TRIAC (AC switch) (102) in OFF position. The firmware in the programmed microcontroller (106) takes several samples of the peak and calculates the average peak without the capacitor (103) connected. The firmware in the programmed microcontroller (106) then turns ON the TRIAC (AC switch) (102) using the TRIAC trigger signal (101) thereby loading the external capacitive step-type fan regulator (100) with the capacitor (103) and then measures the peak of the divided down rectified voltage (105). The firmware in the programmed microcontroller (106) takes several samples of the peak and calculates the average peak with the capacitor (103) connected. The oscilloscope screen shot of the divided down rectified voltage waveform captured with and without the capacitor (103) connected is shown in figure 6.
The firmware in the programmed microcontroller (106) then compares the average peak of the rectified voltage (105) with the capacitor (103) connected and the average peak of the rectified voltage (105) without the capacitor (103) connected. The difference between the two average peak values changes depending on the capacitive step-type fan regulator (100) impedance (Zc) which in turn corresponds to the capacitive step-type fan regulator (100) step position. Thus, based on the difference in value, the programmed microcontroller (106) can determine the capacitive step-type fan regulator (100) step position. The speed of the BLDC motor based ceiling fan is set by the programmed microcontroller (106) based on the determined capacitive step-type fan regulator (100) step position.
The speed control system for a BLDC motor based ceiling fan using wall mounted capacitive step-type fan regulator (100) can be extended to other types of domestic and industrial fans like table fans, air circulator fans etc.
Although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. It is therefore, contemplated that the claims will cover any such modifications or embodiments that fall within the true scope of the invention.
,CLAIMS:WE CLAIM:
1. A speed control system for a BLDC motor based ceiling fan using wall mounted capacitive step-type fan regulator comprises:
at least one Capacitive step-type fan regulator (100);
at least one Programmed microcontroller (106);
at least one TRIAC (AC switch) (102);
at least one Capacitor (103); and
at least one Voltage divider (104),
wherein, the Capacitive step-type fan regulator (100) is fitted on the wall of the building where the ceiling fan is fitted,
wherein, the Capacitive step-type fan regulator (100) consists of a switch (S1) and capacitors,
wherein, the switch (S1) is break-before-make type switch,
wherein, the programmed microcontroller (106) with the firmware algorithm sets the corresponding fan speed, when the user changes the capacitive step-type fan regulator (100) knob position from one position to another, by detecting the capacitive step-type fan regulator (100) knob position change and determining the capacitive step-type fan regulator (100) step position,
wherein, the voltage divider (104) consists of the top resistor (104a) and the bottom resistor (104b) connected in series, with the input voltage applied across the resistor pair and the divided down rectified voltage (105) is emerging from the connection between the top resistor (104a) and the bottom resistor (104b),
wherein, the programmed microcontroller (106) with the firmware algorithm monitors the divided down rectified voltage (105) and detects the capacitive step-type fan regulator (100) knob position change, when the divided down rectified voltage (105) goes less than the value set in the programmed microcontroller (106),
wherein, the programmed microcontroller (106) with the firmware algorithm compares the average peak value of the rectified voltage with the capacitor (103) connected and the average peak value of the rectified voltage without the capacitor (103) connected by turning ON/OFF the TRIAC (AC switch) (102) respectively to determine the step position of the capacitive step-type fan regulator (100) and
wherein, the programmed microcontroller (106) with the firmware algorithm sets the corresponding fan speed during power-on, by determining the step position of the capacitive step-type fan regulator (100).
2. A speed control system for a BLDC motor based ceiling fan using wall mounted capacitive step- type fan regulator (100) as claimed in claim 1, wherein difference in value between the average peak of the rectified voltage with the capacitor (103) connected and without the capacitor (103) connected, will change depending on the change in the impedance (Zc) value of capacitive step-type fan regulator (100), which in turn corresponds to the capacitive step-type fan regulator (100) step position.
3. A speed control system for a BLDC motor based ceiling fan using wall mounted capacitive step-type fan regulator (100) as claimed in claim 1, wherein the capacitive step-type fan regulator (100) is four-step capacitive fan regulator (4 positions).
4. A speed control system for a BLDC motor based ceiling fan using wall mounted capacitive step type fan regulator (100) as claimed in claim 1, wherein the capacitive step-type fan regulator (100) is five-step capacitive fan regulator (5 positions).