CLIAMS:We claim
1)A simple, reliable and cost effective method to command the speed of a BLDC motor based ceiling fan using only a wall-mounted power on/off switch.
2)That the method used in claim 1 eliminates the need for an external infrared remote control unit and an infrared remote receiver.
3)That the method of speed command of claim 1 can be extended to other types of domestic and industrial fans like table fans, air circulator fans and other fans which are based on electronically commutated motors.
,TagSPECI:PRIOR ART:

Ceiling fan speeds are usually regulated by wall-mount voltage regulators (single-phase induction motor based fans), or wall-mount AC/DC converters as in Ref [1], or remote-control as in Ref [2]. The BLDC motor based ceiling fan with infra-red remote control as described in the disclosure of Ref [2] is particularly attractive because of the advantages of low power consumption, constant-speed operation in the face of supply voltage fluctuations, same wiring as the existing fans and the ease of remote operation.

However in some public places where fans are used, such as hospitals, large offices, schools and colleges, remote control option may not be suitable. Our invention demonstrates the solution to such a situation by using the wall mounted ON/OFF switch to command the speed of the fan.

OUR INVENTION:
The present invention proposes to use the wall mounted power on/off switch along with the embedded electronic controller to command the speed of the fan, instead of a remote control. The controller detects the speed commanded by the user by processing the magnitude and timing of the changes in internal DC bus voltage that occurs when the wall switch is switched ON/OFF. The changes are interpreted and processed by the microcontroller appropriately and corresponding speeds are set. The following disclosure illustrates the simplicity and uniqueness of the new invention.

Detailed Description of the Invention:
In the present invention the desired speed can be set by simply turning the wall switch “off” and “on” for the specified count i.e., 1, 2,3, 4, and 5 times to set the 1st,2nd,3rd,4th and 5th speed respectively. This logic is achieved by using the microcontroller [110] of the electronic controller embedded in the motor body. Microcontroller [110] will monitor the bus voltage [109] for a time span of 1.5 seconds every time on power on. If the input wall switch [S1] as shown in Fig 1 and 2 is turned on the bus voltage [109] of the electronic controller will reach its nominal value (around 24V) and when turned off the bus voltage will drop below its the nominal value. When the input wall switch [S1] is turned off and on rapidly bus voltage will oscillate as shown in Fig 5. This change in bus voltage will be monitored by the microcontroller to set the valid count for speed change.

For the microcontroller to increment the count for every power off and on, the change in bus voltage [109] should satisfy the following two conditions within 1.5 seconds.
1. During power on bus voltage [109] should reach the nominal value by crossing the value greater than 18V (Threshold B).
2. During power off the drop down value of bus voltage [109] should cross 18V (Threshold B) and at the same time it should not cross 7.5V (Threshold A).

The flowchart chart in Fig 3 illustrates the algorithm used in the present invention.

When powered on the controller will initialize the count value to zero and time to 1.5 seconds and then starts monitoring the bus voltage [109]. Bus voltage [109] value will be maintained around 24V during the normal running mode as shown in the FIG 4.

FIG 4: BUS VOLTAGE IN RUNNING MODE
If the wall switch [S1] is turned off, the value of bus voltage [109] will drop down to a value and this value should be less than the “threshold B” as shown in FIG 5. If this condition is satisfied the controller will set or increment the valid count. Now if the wall switch is turned on before the bus voltage reaches the Threshold A, then the microcontroller will monitor the similar change in bus voltage for another 1.5 seconds to increment the next valid count.

FIG 5: BUS VOLTAGE DURING POWER OFF AND ON
During the period 1.5 seconds, if there is no change in bus voltage [109] or if bus voltage [109] is not less than the Threshold B then the controller will set the fan speed depending on the last count value obtained and the fan will go to the run mode.

During power off, if the bus voltage [109] crosses the Threshold A as shown in FIG 6 then the microcontroller will get reset. This will put the fan off until the wall switch is turned on.

FIG 6: BUS VOLTAGE CROSSING THRESHOLD B

In the above explained function the time span of 1.5 seconds is chosen so that the user can set the desired speed in an easy way by using the wall switch.

References:
[1] S. Anand and B. G. Fernandes, "Wall mounted speed regulator for a BLDC motor driven ceiling fan", Indian Patent, Appl. No. 542/MUM/2011

[2] M. Sundararajan, K. Durgasharan, N. Ravi, P. Saravanakumar, R. Mahendran,
N. Devendiran, “A cost-effective, sensor-less, and energy-efficient brushless dc
motor with embedded electronic controller for ceiling fans”, Indian patent application number 3505/CHE/2012 A