Low-power radio-frequency receiver

Abstract

A motorized window treatment provides a low-cost solution for controlling the amount of daylight entering a space through a window. The window treatment includes a covering material, a drive shaft, at least one lift cord rotatably received around the drive shaft and connected to the covering material, and a motor coupled to the drive shaft for raising and lowering the covering material. The window treatment also includes a spring assist unit for assisting the motor by providing a torque that equals the torque provided by the weight on the cords that lift the covering material at a position midway between fully-open and fully-closed positions, which helps to minimize motor usage and conserve battery life if a battery is used to power the motorized window treatment. The window treatment may comprise a photosensor for measuring the amount of daylight outside the window and temperature sensors for measuring the temperatures inside and outside of the window. The position of the covering material may be automatically controlled in response to the photosensor and the temperature sensors to save energy, or may also be controlled in response to an infrared or radio-frequency remote control.

Claims

1. A control device responsive to RF signals transmitted by an RF transmitter, the RF transmitter adapted to transmit a number of consecutive packets at a predetermined transmission rate during a given transmission event, each of the consecutive packets characterized by a packet length, the control device comprising: an RF receiver adapted to receive packets from the RF transmitter, the RF receiver configured to be periodically enabled for a sample time period to determine if the RF transmitter is transmitting one of the consecutive packets, the RF receiver configured to enter a sleep mode for a sleep time period between consecutive sample time periods if the RF receiver determines that the RF transmitter is not transmitting one of the consecutive packets during the sample time period; and a controller operatively coupled to the RF receiver, wherein after determining that the RF transmitter is transmitting one of the consecutive packets during the sample time period, the controller is configured to receive a subsequent packet; wherein the sleep time period of the RF receiver is longer than the packet length of each of the consecutive packets, and the sample time period and the sleep time period between sample time periods are sized such that the sample time period coincides with at least one of the predetermined number of consecutive packets in the transmission event.

2. The control device of claim 1, wherein the controller and the RF receiver is configured to be powered by a battery.

3. The control device of claim 1, wherein the controller can be controlled into a sleep mode in which the controller consumes less power than in a normal mode.

4. The control device of claim 1, wherein the controller can be controlled into a sleep mode in which the controller consumes less power than in a normal mode.

5. The control device of claim 1, wherein each of the consecutive packets includes similar data.

6. The control device of claim 1, wherein, after determining that the RF transmitter is transmitting one of the consecutive packets during the sample time period, the control is configured to receive the entire subsequent packet.

7. The control device of claim 1, wherein the sample time period of the RF receiver is less than the packet length.

8. The control device of claim 1, wherein the controller is configured to control an electrical load in response to the subsequent packet received from the RF transmitter.

9. A method of communicating between wireless devices, the method comprising: periodically enabling an RF receiver for a sample time period; in response to RF energy being detected by the RF receiver during the sample time period, determining, via the RF receiver, whether the detected RF energy exceeds a threshold; in response to determining that the detected RF energy exceeds the threshold, putting the RF receiver and a controller in a sleep mode for a snooze time; and subsequent to the snooze time, waking up the RF receiver and the controller, and receiving, via the RF receiver, an entire packet.

10. The method of claim 9, wherein the RF receiver is configured to receive wireless signals sent in consecutive packets with a packet length and a break time between the consecutive packets; wherein the sample time period is less than the packet length; and wherein the snooze time is less than the break time.

11. A system for transmitting wireless signals comprising: a wireless receiver device configured to periodically turn on to determine if a wireless signal is being transmitted, the wireless receiver device configured to receive wireless signals on any of multiple communication channels, the wireless receiver device including a control circuit that determines if the wireless signal is intended for the wireless receiver device; and a wireless transceiver device configured to transmit and receive wireless signals, the wireless transceiver device configured to: receive a packet on a first communication channel; determine that the packet is intended for the wireless receiver; based on the determination that the packet is intended for the wireless receiver, change the communication channel of the wireless transceiver device from the first communication channel to a second communication channel; and subsequent to the retransmission of the packet, change the communication channel of the wireless transceiver device from the second communication channel to the first communication channel.

12. The method of claim 11, wherein the wireless receiver device is configured to receive fewer wireless signals on the second communication channel than if the wireless receiver device were receiving wireless signals on the first communication channel, thereby causing the wireless receiver device to turn on for less time and reduce battery power consumption.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described in greater detail in the following detailed description with reference to the drawings in which:

(2) FIG. 1 is a perspective view of a motorized window treatment system having a battery-powered motorized window treatment and a remote control according to a first embodiment of the present invention;

(3) FIG. 2 is a perspective view of the battery-powered motorized window treatment of FIG. 1 in a full-opened position;

(4) FIG. 3 is a right side view of the battery-powered motorized window treatment of FIG. 1;

(5) FIG. 4 is a front view of the battery-powered motorized window treatment of FIG. 1;

(6) FIG. 5 is a simplified block diagram of a motor drive unit of the battery-powered motorized window treatment of FIG. 1;

(7) FIGS. 6A and 6B are partial perspective views of the motor drive unit and a headrail of the motorized window treatment of FIG. 1;

(8) FIG. 7 is simplified frequency response of an RF filter of the motor drive unit of FIG. 5;

(9) FIG. 8 is a simplified timing diagram of an RF data transmission event and a sampling event of the motor drive unit of FIG. 5;

(10) FIG. 9 is a simplified flowchart of an RF signal receiving procedure executed by a controller of the motor drive unit of FIG. 5;

(11) FIG. 10 is a simplified flowchart of a command procedure executed periodically by the controller of the motor drive unit of FIG. 5;

(12) FIG. 11 is a simplified flowchart of a motor control procedure executed periodically by the controller of the motor drive unit of FIG. 5;

(13) FIG. 12 is a simplified diagram of a radio-frequency load control system including multiple motorized window treatments according to a second embodiment of the present invention;

(14) FIG. 13 is a simplified block diagram of a dimmer switch of the load control system of FIG. 12 according to the second embodiment of the present invention;

(15) FIG. 14 is a simplified block diagram of a dimmer switch of the load control system of FIG. 12 according to an alternate embodiment of the present invention;

(16) FIG. 15 is a simplified flowchart of an RF sampling rate selection procedure executed by a controller of one of the battery-powered motorized window treatments of FIG. 12;

(17) FIG. 16 is a simplified graph illustrating various signal strength thresholds of one of the battery-powered motorized window treatments of FIG. 12;

(18) FIG. 17 is a simplified flowchart of an RF monitoring procedure performed by a signal repeater of the load control system of FIG. 12;

(19) FIG. 18 is a simplified flowchart of an RF signal receiving procedure performed by a signal repeater of the load control system of FIG. 12; and

(20) FIG. 19 is a simplified diagram of a RF load control system having two signal repeaters coupled together via a digital communication link according to a third embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(21) The foregoing summary, as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purposes of illustrating the invention, there is shown in the drawings an embodiment that is presently preferred, in which like numerals represent similar parts throughout the several views of the drawings, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed.

(22) FIG. 1 is a perspective view of a motorized window treatment system 100 having a battery-powered motorized window treatment 110 mounted in an opening 102, for example, in front of a window 104, according to a first embodiment of the present invention. The battery-powered motorized window treatment 110 comprises a covering material, for example, a cellular shade fabric 112 as shown in FIG. 1. The cellular shade fabric 112 has a top end connected to a headrail 114 (that extends between two mounting plates 115) and a bottom end connected to a weighting element 116. The mounting plates 115 may be connected to the sides of the opening 102 as shown in FIG. 1, such that the cellular shade fabric 112 is able to hang in front of the window 104, and may be adjusted between a fully-open position P.sub.FULLY-OPEN and a fully-closed position P.sub.FULLY-CLOSED to control the amount of daylight entering a room or space. Alternatively, the mounting plates 115 of the battery-powered motorized window treatment 110 could be mounted externally to the opening 102 (e.g., above the opening) with the shade fabric 112 hanging in front of the opening and the window 104. In addition, the battery-powered motorized window treatment 110 could alternatively comprise other types of covering materials, such as, for example, a plurality of horizontally-extending slats (i.e., a Venetian or Persian blind system), pleated blinds, a roller shade fabric, or a Roman shade fabric.

(23) The motorized window treatment system 100 comprises a radio-frequency (RF) remote control 190 for transmitting RF signals 106 to the motorized window treatment 110 using, for example, a frequency-shift keying (FSK) modulation technique, to thus for control the operation of the motorized window treatment. Specifically, the RF remote control 190 is operable to transmit digital messages including commands to control the motorized window treatment 710 via the RF signals 106 in response to actuations of a plurality of buttons, e.g., an open button 192, a close button 194, a raise button 195, a lower button 196, and a preset button 198. The motorized window treatment 110 controls the cellular shade fabric 112 to the fully-open position P.sub.FULLY-OPEN and the fully-closed position P.sub.FULLY-CLOSED in response to actuations of the open button 192 and the close button 194 of the remote control 190, respectively. The motorized window treatment 110 raises and lowers the cellular shade fabric 112 in response to actuations of the raise button 195 and the lower button 196, respectively. The motorized window treatment 110 controls the cellular shade fabric 112 to a preset position P.sub.PRESET in response to actuations of the preset button 198.

(24) FIG. 2 is a perspective view and FIG. 3 is a right side view of the battery-powered motorized window treatment 110 with the cellular shade fabric 112 in the fully-open position P.sub.FULLY-OPEN. The motorized window treatment 110 comprises a motor drive unit 120 for raising and lowering the weighting element 116 and the cellular shade fabric 112 between the fully-open position P.sub.FULLY-OPEN and the fully-closed position P.sub.FULLY-CLOSED. By controlling the amount of the window 104 covered by the cellular shade fabric 112, the motorized window treatment 110 is able to control the amount of daylight entering the room. The headrail 114 of the motorized window treatment 110 comprises an internal side 122 and an opposite external side 124, which faces the window 104 that the shade fabric 112 is covering. The motor drive unit 120 comprises an actuator 126, which is positioned adjacent the internal side 122 of the headrail 114 may may be actuated when a user is configuring the motorized window treatment 110. The actuator 126 may be made of, for example, a clear material, such that the actuator may operate as a light pipe to conduct illumination from inside the motor drive unit 120 to thus be provide feedback to the user of the motorized window treatment 110. The motor drive unit 120 is operable to determine a target position P.sub.TARGET for the weighting element 116 in response to commands included in the IR signals received from the remote control 118 and to subsequently control a present position P.sub.PRES of the weighting element to the target position P.sub.TARGET. As shown in FIG. 2A, a top side 128 of the headrail 114 is open, such that the motor drive unit 120 may be positioned inside the headrail and the actuator 126 may protrude slightly over the internal side 122 of the headrail.

(25) FIG. 4 is a front view of the battery-powered motorized window treatment 110 with a front portion of the headrail 114 removed to show the motor drive unit 120. The motorized window treatment 110 comprises lift cords 130 that extend from the headrail 114 to the weighting element 116 for allowing the motor drive unit 120 to raise and lower the weighting element. The motor drive unit 120 includes an internal motor 150 (FIG. 5) coupled to drive shafts 132 that extend from the motor on each side of the motor and are each coupled to a respective lift cord spool 134. The lift cords 130 are windingly received around the lift cord spools 134 and are fixedly attached to the weighting element 116, such that the motor drive unit 120 is operable to rotate the drive shafts 132 to raise and lower the weighting element. The motorized window treatment 110 further comprises two constant-force spring assist assemblies 135, which are each coupled to the drive shafts 132 adjacent to one of the two lift cord spools 134. Each of the lift cord spools 134 and the adjacent constant-force spring assist assembly 135 are housed in a respective lift cord spool enclosure 136 as shown in FIG. 3. Alternatively, the motor drive unit 120 could be located at either end of the headrail 114 and the motorized window treatment 110 could comprise a single drive shaft that extends along the length of the headrail and is coupled to both of the lift cord spools 134.

(26) The battery-powered motorized window treatment 110 also comprises a plurality of batteries 138 (e.g., four D-cell batteries), which are electrically coupled in series. The seris-combination of the batteries 138 is coupled to the motor drive unit 120 for powering the motor drive unit. The batteries 138 are housed inside the headrail 114 and thus out of view of a user of the motorized window treatment 110. Specifically, the batteries 138 are mounted in two battery holders 139 located inside the headrail 114, such that there are two batteries in each battery holder as shown in FIG. 4. According to the embodiments of the present invention, the batteries 138 provide the motorized window treatment 110 with a practical lifetime (e.g., approximately three years), and are typical “off-the-shelf” batteries that are easy and not expensive to replace. Alternatively, the motor drive unit 120 could comprise more batteries (e.g., six or eight) coupled in series or batteries of a different kind (e.g., AA batteries) coupled in series.

(27) FIG. 5 is a simplified block diagram of the motor drive unit 120 of the battery-powered motorized window treatment 110. The motor drive unit 120 comprises a controller 152 for controlling the operation of the motor 150, which may comprise, for example, a DC motor. The controller 152 may comprise, for example, a microprocessor, a programmable logic device (PLD), a microcontroller, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any suitable processing device or control circuit. The controller 152 is coupled to the actuator 126 for receiving user inputs in response to actuations of the actuator 126. The controller 152 is also coupled to an H-bridge motor drive circuit 154 for driving the motor 150 via a set of drive signals V.sub.DRIVE to control the weighting element 116 and the cellular shade fabric 112 between the fully-open position P.sub.FULLY-OPEN and the fully-closed position P.sub.FULLY-CLOSED. The controller 152 is operable to rotate the motor 150 at a constant rotational speed by controlling the H-bridge motor drive circuit 154 to supply a pulse-width modulated (PWM) drive signal having a constant duty cycle to the motor. The controller 152 is able to change the rotational speed of the motor 150 by adjusting the duty cycle of the PWM signal applied to the motor and to change the direction of rotation of the motor by changing the polarity of the PWM drive signal applied to the motor.

(28) The controller 152 receives information regarding the rotational position and direction of rotation of the motor 150 from a rotational position sensor, such as, for example, a transmissive optical sensor circuit 155. The rotational position sensor may also comprise other suitable position sensors or sensor arrangements, such as, for example, Hall-effect, optical, or resistive sensors. The controller 152 is operable to determine a rotational position of the motor 150 in response to the transmissive optical sensor circuit 155, and to use the rotational position of the motor to determine a present position P.sub.PRES of the weighting element 116. The controller 152 may comprise an internal non-volatile memory (or alternatively, an external memory coupled to the controller) for storage of the present position P.sub.PRES of the shade fabric 112, the fully open position P.sub.FULLY-OPEN, and the fully closed position P.sub.FULLY-CLOSED. The operation of the H-bridge motor drive circuit 154 and the use of sensor devices to track the direction and speed of the motor drive unit 120 is described in greater detail in commonly-assigned U.S. Pat. No. 5,848,634, issued Dec. 15, 1998, entitled MOTORIZED WINDOW SHADE SYSTEM, and commonly-assigned U.S. Pat. No. 6,497,267, issued Dec. 24, 2002, entitled MOTORIZED WINDOW SHADE WITH ULTRAQUIET MOTOR DRIVE AND ESD PROTECTION, the entire disclosures of which are herein incorporated by reference.

(29) A user of the window treatment system 100 is able to adjust the position of the weighting element 116 and the cellular shade fabric 112 by using the remote control 190 to transmit commands to the motor drive unit 120 via the RF signals 106. The motor drive unit 120 comprises an RF receiver 166 coupled to an antenna 168 (e.g., a wire antenna) for receiving the RF signals 102. The antenna 168 is coupled to the RF receiver 166 via a surface acoustic wave (SAW) filter 169 (e.g., part number B3580 as manufactured by Epcos AG), which acts to filter RF noise as will be described in greater detail below. The RF receiver 166 is operable to provide an RF data control signal V.sub.RF-DATA representative of the received RF signals 102 to a controller 152, such that the controller is operable to control the H-bridge motor drive circuit 154 in response to the received signals.

(30) FIGS. 6A and 6B are partial perspective views of the motor drive unit 120 and the headrail 114 of the motorized window treatment 110 of the second embodiment. The antenna 168 is adapted to extend from the motor drive unit 168 and is received in an elongated antenna wire carrier 170. As shown in FIG. 6A, the antenna wire carrier 170 may be located in a first position immediately adjacent the motor drive unit 120 above the external side 124 of the headrail 114. The antenna wire carrier 170 may be removed from the first position and re-located into a second position in which the antenna 168 is slightly offset (e.g., by a distance of approximately 0.4 inch) from the motor drive unit 120 as shown in FIG. 6B. The antenna wire carrier 170 comprises clips 172 that are adapted to snap onto the top edge of the external side 124 of the headrail 114 in the second position. The antenna wire carrier 170 provides a mechanical means for adjusting the RF sensitivity of the RF receiver 166 and thus the power consumed by the RF receiver 166. When the antenna wire carrier 170 is located in the second position (as shown in FIG. 6B), the RF receiver 166 has an increased RF sensitivity (e.g., by approximately 3 dB), and is thus operable to receive more RF signals 102 than if the antenna wire carrier was located in the first position (as shown in FIG. 6A). However, the increased RF sensitivity means that the RF receiver 166 will consume more power. Therefore, the antenna wire carrier 170 may be moved to the first position in which the RF receiver 166 has a reduced RF sensitivity, but consumes less power.

(31) As shown in FIG. 5, the motor drive unit 120 receives power from the series-coupled batteries 138, which provide a battery voltage V.sub.BATT. For example, the batteries 138 may comprise D-cell batteries having rated voltages of approximately 1.5 volts, such that the battery voltage V.sub.BATT has a magnitude of approximately 6 volts. The H-bridge motor drive circuit 154 receives the battery voltage V.sub.BATT for driving the motor 150. In order to preserve the life of the batteries 138, the controller 152 may be operable to operate in a sleep mode when the motor 150 is idle.

(32) The motor drive unit 120 further comprises a power supply 156 (e.g., a linear regulator) that receives the battery voltage V.sub.BATT and generates a DC supply voltage V.sub.CC for powering the controller 152 and other low-voltage circuitry of the motor drive unit. The controller 152 is coupled to the power supply 156 and generates a voltage adjustment control signal V.sub.ADJ for adjusting the magnitude of the DC supply voltage V.sub.CC between a first nominal magnitude (e.g., approximately 2.7 volts) and a second increased magnitude (e.g., approximately 3.3 volts). The power supply 156 may comprise, for example, an adjustable linear regulator having one or more feedback resistors that are switched in and out of the circuit by the controller 152 to adjust the magnitude of the DC supply voltage V.sub.CC. The controller 152 may adjust the magnitude of the DC supply voltage V.sub.CC to the second increased magnitude while the controller is driving the FETs Q.sub.1-Q.sub.4 of the motor drive circuit 154 to rotate the motor 150 (since the controller may require an increased supply voltage to drive the gates of the FETs). The controller 152 adjusts the magnitude of the DC supply voltage V.sub.CC to the first nominal magnitude when the controller is not controlling the motor drive circuit 154 to rotate the motor 150 (e.g., when the controller is in the sleep mode). The magnitude of the idle currents drawn by the controller 152, the IR receiver 166, and other low-voltage circuitry of the motor drive unit 120 may be significantly smaller when these circuits are powered by the first nominal magnitude of the DC supply voltage V.sub.CC.

(33) The controller 152 is operable to determine that the magnitude of the battery voltage V.sub.BATT is getting low and to operate in a low-battery mode when the magnitude of the battery voltage V.sub.BATT drops below a first predetermined battery-voltage threshold V.sub.B-TH1 (e.g., approximately 1.0 volts per battery). For example, the controller 152 may control the motor drive circuit 154 so that the motor 150 is operated at a reduced speed (e.g., at half speed) to conserve battery power when the controller 152 is operating in the low-battery mode. This would serve as an indication to a consumer that the battery voltage V.sub.BATT is low and the batteries 138 need to be changed.

(34) When the magnitude of the battery voltage V.sub.BATT drops below a second predetermined battery-voltage threshold V.sub.B-TH2 (less than the first predetermined battery-voltage threshold V.sub.B-TH1, e.g., approximately 0.9 V per battery) while operating in the low-battery mode, the controller 152 may shut down electrical loads in the motor drive unit 120 (e.g., by disabling the IR receiver 166 and other low-voltage circuitry of the motor drive unit) and prevent movements of the cellular shade fabric 112 except to allow for at least one additional movement of the cellular shade fabric to the fully-open position P.sub.FULLY-OPEN. Having the cellular shade fabric 112 at the fully-open position P.sub.FULLY-OPEN allows for easy replacement of the batteries. The second predetermined battery-voltage threshold V.sub.B-TH2 may be sized to provide enough reserve energy in the batteries 138 to allow for the at least one additional movement of the cellular shade fabric 112 and the weighting element 116 to the fully-open position P.sub.FULLY-OPEN.

(35) When the magnitude of the battery voltage V.sub.BATT drops below a third predetermined battery-voltage threshold V.sub.B-TH3 (less than the second predetermined battery-voltage threshold V.sub.B-TH2, e.g., approximately 0.8 V per battery), the controller 152 may be operable to shut itself down such that no other circuits in the motor drive unit 120 consume any power in order to protect against any potential leakage of the batteries 138.

(36) The motor drive unit 120 comprises an alternate (or supplemental) power source, such as a backup battery, e.g., a long-lasting battery (not shown), which generates a backup supply voltage V.sub.BACKUP (e.g., approximately 3.0 volts) for powering the controller 152. The alternate power source provides the controller 152 with power when the batteries 138 are removed for replacement, or otherwise depleted, such that the position data relating to the position of the window treatment that is stored in the memory of the controller 152 is maintained. Alternatively, a large bus capacitor or an ultra-capacitor can be coupled to the controller 152 (rather than the backup battery), so that even when the batteries 138 are removed for replacement, an adequate charge will remain in the bus capacitor or ultra capacitor to maintain adequate voltage to keep the controller 152 charged for the period of time necessary to replace batteries 138 and thereby prevent loss of stored data in the memory of the controller.

(37) These embodiments allow the motor drive unit 120 to keep track of the position of the weighting element 116 of the window treatment 110 even when the batteries 138 are removed and the window treatment is manually operated (i.e., pulled). In such embodiments, the controller 152 continues to receive signals from transmissive optical sensor circuit 155, even when the batteries 138 are removed. Because it remains powered, the controller 152 will continue to calculate the position of the window treatment 110 when manually adjusted. It should be pointed out that the window treatment 110 of the present invention allows a user at any time to manually adjust the position of the window treatment, and that the position of the window treatment is always calculated both when the window treatment is moved by the motor or manually.

(38) Another feature of the invention is that the controller 152 is preferably arranged to prevent the motor drive circuit 154 from operating to lower the cellular shade fabric 112 until an upper limit for the fabric is reset after a loss of power, e.g., if the batteries 138 are depleted. Thus, the motor drive unit 120 will not lower from the current raised position in the event of power loss. The user will be required to raise the cellular shade fabric 112 to the fully-open position before being able to lower the shade fabric.

(39) As shown in FIG. 5, the motor drive unit 120 comprises an internal temperature sensor 160 that is located adjacent the internal side 122 of the headrail 114 (i.e., a room-side temperature sensor), and a external temperature sensor 162 that is located adjacent the external side 124 of the headrail (i.e., a window-side temperature sensor). The room-side temperature sensor 160 is operable to measure an interior temperature T.sub.INT inside the room in which the motorized window treatment 110 is installed, while the external temperature sensor 162 is operable to measure an exterior temperature TEXT between the headrail 114 and the window 104. The motor drive unit 120 further comprises a photosensor 164, which is located adjacent the external side 124 of the headrail 114, and is directed to measure the amount of sunlight that may be shining on the window 104. Alternatively, the exterior (window-side) temperature sensor 162 may be implemented as a sensor label (external to the headrail 114 of the battery powered motorized window treatment 110) that is operable to be affixed to an inside surface of a window. The sensor label may be coupled to the motor drive unit 120 through low voltage wiring (not shown).

(40) The controller 152 receives inputs from the internal temperature sensor 160, the external temperature sensor 162, and the photosensor 164. The controller 152 may operate in an eco-mode to control the position of the weighting element 116 and the cellular shade fabric 112 in response to the internal temperature sensor 160, the external temperature sensor 162, and the photosensor 164, so as to provide energy savings. When operating in the eco-mode, the controller 152 adjusts the amount of the window 104 covered by the cellular shade fabric 112 to attempt to save energy, for example, by reducing the amount of electrical energy consumed by other control systems in the building in which the motorized window treatment 110 is installed. For example, the controller 152 may adjust the present position P.sub.PRES of the weighting element 116 to control the amount of daylight entering the room in which the motorized window treatment 110 is installed, such that lighting loads in the room may be turned off or dimmed to thus save energy. In addition, the controller 152 may adjust the present position P.sub.PRES of the weighting element 116 to control the heat flow through the window 104 in order to lighten the load on a heating and/or cooling system, e.g., a heating, air-conditioning, and ventilation (HVAC) system, in the building in which the motorized window treatment 110 is installed.

(41) The motorized window treatment 110 and the RF remote control 190 may be easily programmed, such that the motorized window treatment 110 is responsive to actuations of the buttons 192-198 of the remote control 118. First, the user may associate the remote control 190 with the motorized window treatment 110 by actuating the actuator 126 on the motor drive unit 120 and then pressing and holding, for example, the close button 194 on the remote control for a predetermined amount of time (e.g., approximately five seconds). After the remote control 190 is associated with the motorized window treatment 110, the motorized window treatment is responsive to the RF signals 106 transmitted by the remote control. The user may program the preset position P.sub.PRESET of the motorized window treatment 110 by actuating the raise and lower buttons 195, 196 of the remote control 190 to adjust the position of the weighting element 116 to the desired preset position, and then pressing and holding the preset button 198 for the predetermined amount of time.

(42) The user may also use the remote control 190 to program the upper and lower limits (i.e., the fully-open position P.sub.FULLY-OPEN and the fully-closed position P.sub.FULLY-CLOSED) of the motorized window treatments 110. To enter a limit programming mode, the user actuates the actuator 126 on the motor drive unit 120, and then simultaneously presses and holds the open button 192 and the raise button 195 of the remote control 190 for the predetermined amount of time (i.e., approximately five seconds). To program the lower limit, the user actuates the raise and lower buttons 195, 196 of the remote control 190 to adjust the position of the weighting element 116 to the desired fully-closed position P.sub.FULLY-CLOSED, and then presses the close button 194 for the predetermined amount of time. To program the upper limit, the user actuates the raise and lower buttons 195, 196 of the remote control to adjust the position of the weighting element 116 to the desired fully-open position P.sub.FULLY-OPEN, and then presses the open button 192 for the predetermined amount of time. The user can then press and hold the open button 192 and the raise button 195 of the remote control 190 for the predetermined amount of time to exit the limit programming mode.

(43) The RF receiver 166 and the controller 152 are both able to operate in a sleep mode (i.e., low-power mode) to conserve battery power. During the sleep mode, the RF receiver 166 is operable to wake-up periodically to sample (e.g., listen for) any RF signals 106 as will be described in greater detail below. In the event that the RF receiver 166 does detect the presence of any RF signals 106, the RF receiver is operable to wake up the controller 152 via an RF wake up signal V.sub.RF_WAKE, such that the controller can begin processing the received RF signal. In particular, the RF receiver 166 wakes up the controller 152 in response to detecting any RF energy within a particular frequency band. Each time that the controller 152 wakes up in response to the RF wake up signal V.sub.RF_WAKE, additional power is consumed by the controller (since the controller is fully powered when awake). This additional power consumption reduces the life of the batteries 138, and as a result, it is optimal that the RF receiver 166 only wake the controller 152 when necessary.

(44) FIG. 7 shows an example of a simplified frequency response of the SAW filter 169. Frequency 180 illustrates an example frequency of the RF signals 102. A frequency response 182 illustrates the response of only the antenna 168 and the RF receiver 166 (i.e., the response without the SAW filter 169). As shown in FIG. 7, the frequency response 182 spans a wide range of frequencies (e.g., up to an 80 MHz band). As a result, the RF receiver 166 may be responsive to an interference event 184. In particular, the RF receiver 166 (without the presence of the SAW filter 169) will detect the presence of the interference event 184, and as a result, will cause the controller 152 to wake up via the RF wake up signal V.sub.RF_WAKE. As the controller 152 begins to process the interference event 184, the controller will appropriately disregard this interference event as it will recognize that it is not an RF signal 106. However as mentioned above, the controller 152 consumes additional power to process the interference event 184, and this negatively impacts the life of the batteries 138. FIG. 7 also illustrates a SAW frequency response 186 which spans a much narrower band of frequencies than frequency response 182. In particular, the SAW frequency response 186 does not encompass the interference event 184. As a result, the SAW filter 169 filters interference events (e.g., such as interference event 184), and this allows the controller 152 to not wake up unnecessarily, thus further conserving the life of the batteries 138.

(45) FIG. 8 is a simplified timing diagram of a data transmission event transmitted by the RF remote control 190 to the motorized window treatment 110 and a sampling event of the RF receiver 166 of the motor drive unit 120. The remote control 190 transmits packets of data (e.g., the control information) via the RF signals 106 with each packet having a packet time period T.sub.PACKET (e.g, approximately 5 msec). Each packet of data is typically transmitted multiple times (e.g., up to twelve times) during a given data transmission event. Between each packet of data, there is a packet break time period T.sub.PKT_BRK (e.g., approximately 75 ms), such that the remote control transmits digital messages at a transmission rate of approximately 12.5 packets per second. The RF receiver 166 of the motor drive unit 120 is operable to wake up and listen for any RF signals 106 during an RF sampling time period T.sub.SMPL-RF. If no RF signals 106 are detected during the RF sample time period T.sub.SMPL-RF, then the RF receiver 166 goes to sleep for an RF sleep time period T.sub.SLP-RF, such that the RF receiver samples the RF data at a sampling period T.sub.SAMPLE. Alternatively, the break time period T.sub.PKT_BRK could not be a fixed value, but could be a varying or random time between each of the transmitted packets.

(46) The RF sample time period T.sub.SMPL-RF and the RF sleep time period T.sub.SLP-RF the RF receiver 166 are sized appropriately to ensure that the RF sample time period T.sub.SMPL-RF coincides with at least one packet of a predetermined number of consecutive packets of a data transmission event. As a result, the RF sleep time period T.sub.SLP-RF of the RF receiver 166 can be much longer than the packet time period T.sub.PACKET. In addition, the RF sample time period T.sub.SMPL-RF can be significantly shorter than the packet time period T.sub.PACKET. Accordingly, the RF receiver 166 is operable to sleep for longer periods of time than prior art RF receivers, thus extending the lifetime of the batteries 138 of the motor drive unit 120. For example, the RF sample time period T.sub.SMPL-RF and the RF sleep time period T.sub.SLP-RF may be sized to be approximately 0.1 msec and 17.8 msec, respectively, to ensure that the RF sample time period T.sub.SMPL-RF coincides with at least one packet of five consecutive packets of a data transmission event.

(47) Four packets 200, 202, 204, and 206 of a data transmission event are shown in FIG. 8. At time to, the remote control 190 begins to transmit the first packet 200 via the RF signals 106. The first packet 200 is not received by the RF receiver 166 because the packet is transmitted during the RF sleep time period T.sub.SLP-RF (i.e., while the RF receiver is sleeping). In other words, the transmission of packet 200 does not coincide with an RF sampling event 210 of the RF receiver. Similarly, the second packet 202 transmitted at time t.sub.1 is not received by the RF receiver 166 because the packet is transmitted during the RF sleep time T.sub.SLP-RF and does not coincide with one of the RF sampling events 210 of the RF receiver 166.

(48) At time t.sub.2, the third packet 204 is transmitted and is detected by the RF receiver 166, such that the RF receiver wakes up the controller 152. Since the controller 152 wakes up in the middle of the transmission of the third packet 204 (i.e., has missed the beginning of the transmission of the third packet), the controller is unable to properly process the data contained within the third packet. However, the controller 152 is operable to process the third packet 204 sufficiently to determine that a fourth packet 206 will be transmitted after the packet break time period T.sub.PKT_BRK. Accordingly, the controller 152 and the RF receiver 166 are operable to enter the sleep mode for a snooze time period T.sub.SNOOZE, which may be approximately equal to or slightly less than the packet break time period T.sub.PKT_BRK. As shown in FIG. 8, the snooze time period T.sub.SNOOZE expires just before time t.sub.3, when the fourth packet 206 is transmitted. In other words, the duration of the snooze time period T.sub.SNOOZE is short enough to ensure that the RF receiver 166 is awake in time to receive the complete transmission of the fourth packet 206.

(49) When the snooze time period T.sub.SNOOZE expires, the RF receiver 166 and the controller 152 wake up, and the RF transceiver begins to listen to RF signals 102 for at least the RF sample time period T.sub.SMPL-RF. Because the RF receiver 166 and the controller 152 are awake at time t.sub.3 when the remote control 190 begins to transmit the fourth packet 206, the receiver is able to receive the entire packet. The receiver 166 remains on for an RF on time period T.sub.ON-RF and is operable to receive the entire packet 206 during an RF receiving event 212, such that the controller 152 is able to properly process the packet 206 of data. Thus, because the RF receiver 166 and the controller 152 go back to sleep during the snooze time period T.sub.SNOOZE (and do not stay awake and fully powered while waiting for the next packet to be transmitted), the life of the batteries 138 is further conserved.

(50) FIG. 9 is a simplified flowchart of an RF signal receiving procedure 300 executed by the controller 152 after being awakened in response to the RF wake up signal V.sub.RF_WAKE at step 310. The controller 152 uses a SNOOZE flag to keep track of when the RF receiver 166 has been put to sleep for the snooze time period T.sub.SNOOZE. If the SNOOZE flag is not set at step 312 (i.e., the RF receiver 166 has not been put to sleep for the snooze time period T.sub.SNOOZE) and the controller 152 does not detect an indication that an RF signal is present at step 314, the controller 152 simply goes back to sleep at step 316 and the RF signal receiving procedure 300 exits. However, if the controller 152 detects an RF signal at step 314, the controller sets the SNOOZE flag at step 318, and puts the RF receiver to sleep for the snooze time period T.sub.SNOOZE at step 320. The controller 152 then goes back to sleep at step 316, before the RF signal receiving procedure 300 exits.

(51) If the SNOOZE flag is set at step 312 (i.e., the RF receiver 166 has been put to sleep for the snooze time period T.sub.SNOOZE), the controller 152 first clears the SNOOZE flag at step 322 and then gets ready to receive a digital message. If the RF receiver 766 is not receiving the start of a digital message at step 324, the controller 152 puts the RF receiver to sleep for the RF sleep time period T.sub.SLP-RF at step 326 and goes back to sleep at step 316, before the RF signal receiving procedure 300 exits. However, if the RF receiver 166 is receiving the start of a digital message at step 324, the controller 152 stores the received message in a receive (RX) buffer at step 328 and puts the RF receiver to sleep for the RF sleep time period T.sub.SLP-RF at step 330. The RF signal receiving procedure 300 exits without the controller 152 being put back to sleep. The controller 152 will go back to sleep after processing the received digital message.

(52) FIG. 10 is a simplified flowchart of a command procedure 400 executed periodically by the controller 152. If there is not a command in the RX buffer at step 410, the command procedure 400 simply exits. However, if there is an open command in the RX buffer at step 412, the controller 152 sets the target position P.sub.TARGET equal to the fully-open position P.sub.FULLY-OPEN at step 414, before the command procedure 400 exits. If the received command is a close command at step 416, the controller 152 sets the target position P.sub.TARGET equal to the fully-closed position P.sub.FULLY-CLOSED at step 418 and the command procedure 400 exits. If the received command is a raise command at step 420 or a lower command at step 424, the controller 152 respectively increases the target position P.sub.TARGET by a predetermined increment ΔP at step 422 or decreases the target position P.sub.TARGET by the predetermined increment ΔP at step 426, before the command procedure 400 exits.

(53) FIG. 11 is a simplified flowchart of a motor control procedure 500 executed periodically by the controller 152 (e.g., every two msec). If the motor 150 is not presently rotating at step 510 and the present position P.sub.PRES is equal to the target position P.sub.TARGET at step 512, the motor control procedure 500 simply exits without controlling the motor. However, if the motor 150 is not presently rotating at step 510 and the present position P.sub.PRES is not equal to the target position P.sub.TARGET at step 512, the controller 152 controls the voltage adjustment control signal V.sub.ADJ to adjust the magnitude of the DC supply voltage V.sub.CC to the increased magnitude (i.e., approximately 3.3 volts) at step 514. The controller 152 then begins to control the H-bridge drive circuit 154 to drive the motor 150 appropriately at step 516, so as to move the weighting element 116 towards the target position P.sub.TARGET. If the motor 150 is presently rotating at step 510, but the present position P.sub.PRES is not yet equal to the target position P.sub.TARGET at step 518, the controller 512 continues to drive the motor 150 appropriately at step 520 and the motor control procedure 500 exits. If the motor 150 is presently rotating at step 510 and the present position P.sub.PRES is now equal to the target position P.sub.TARGET at step 518, the controller 152 stops driving the motor at step 522 and controls the voltage adjustment control signal V.sub.ADJ to adjust the magnitude of the DC supply voltage V.sub.CC to the nominal magnitude (i.e., approximately 2.7 volts) at step 524.

(54) As previously mentioned, the controller 152 operates in a low-battery mode when the magnitude of the battery voltage V.sub.BATT is getting low. Specifically, if the magnitude of the battery voltage V.sub.BATT has dropped below the first battery-voltage threshold V.sub.B-TH1 at step 526, the controller 152 begins at step 528 to operate in the low-battery mode during which the controller 152 will operate the motor at a reduced speed (i.e., at half speed). If the magnitude of the battery voltage V.sub.BATT is less than or equal to the second battery-voltage threshold V.sub.B-TH2 at step 530, the controller 152 allows for one last movement of the cellular shade fabric 112 and the weighting element 116 to the fully-open position P.sub.FULLY-OPEN by setting a FINAL_MOVE flag in memory at step 532. At step 534, the controller 152 shuts down all unnecessary loads of the motor drive unit 120 (e.g., the external temperature sensor 162, the photosensor 164, the internal temperature sensor 160, and the IR receiver 166) and prevents the motor 150 from moving the cellular shade fabric 112 and the weighting element 116 except for one last movement to the fully-open position P.sub.FULLY-OPEN. If the magnitude of the battery voltage V.sub.BATT is less than or equal to the third battery-voltage threshold V.sub.B-TH3 at step 536, the controller 152 shuts itself down at step 538 such that no other circuits in the motor drive unit 120 consume any power to thus protect against any potential leakage of the batteries 138. Otherwise, the motor control procedure 500 exits.

(55) The battery-powered motorized window treatment 110 is described in greater detail in U.S. Patent Application Ser. No. 13/415,084, filed Mar. 8, 2012, entitled MOTORIZED WINDOW TREATMENT, the entire disclosures of which are hereby incorporated by reference. While the battery-powered motorized window treatment 110 of the first embodiment comprises the cellular shade fabric 112, the low-power RF receiver 166 could alternatively be used in other types of motorized window treatments, such as, for example, roller shades, draperies, Roman shades, Venetian blinds, and tensioned roller shade systems. An example of a roller shade system is described in greater detail in commonly-assigned U.S. Pat. No. 6,983,783, issued Jan. 10, 2006, entitled MOTORIZED SHADE CONTROL SYSTEM, the entire disclosure of which is hereby incorporated by reference. An example of a drapery system is described in greater detail in commonly-assigned U.S. Pat. No. 6,994,145, issued Feb. 7, 2006, entitled MOTORIZED DRAPERY PULL SYSTEM, the entire disclosure of which is hereby incorporated by reference. An example of a Roman shade system is described in greater detail in commonly-assigned U.S. patent application Ser. No. 12/784,096, filed Mar. 20, 2010, entitled ROMAN SHADE SYSTEM, the entire disclosure of which is hereby incorporated by reference. An example of a Venetian blind system is described in greater detail in commonly-assigned U.S. patent application Ser. No. 13/233,828, filed Sep. 15, 2011, entitled MOTORIZED VENETIAN BLIND SYSTEM, the entire disclosure of which is hereby incorporated by reference. An example of a tensioned roller shade system is described in greater detail in commonly-assigned U.S. Pat. No. 8,056,601, issued Nov. 15, 2011, entitled SELF-CONTAINED TENSIONED ROLLER SHADE SYSTEM, the entire disclosure of which is hereby incorporated by reference.

(56) FIG. 12 is a simplified diagram of a radio frequency (RF) load control system 600 having multiple battery-powered motorized window treatments 610 according to a second embodiment of the present invention. The battery-powered motorized window treatments 610 of the second embodiment each have a very similar structure as the battery-powered motorized window treatment 110 of the first embodiment (as shown in FIG. 5). However, each of the motorized window treatments 610 of the second embodiment comprises a motor drive unit 620 having an RF transceiver (not shown) rather than the RF receiver 166, such that the motorized window treatments are operable to both transmit and receive RF signals 606. The control devices of the load control system 600 are operable to transmit packets using a packet time period T.sub.PACKET (e.g., approximately 5 msec) and a packet break time period T.sub.PKT_BRK (e.g., approximately 75 msec) as in the second embodiment.

(57) As in the first embodiment, each motorized window treatment 610 is operable to enable the RF transceiver at a sampling period T.sub.SAMPLE (e.g., approximately 17.8 msec) to detect if an RF signal 602 is presently being transmitted. Each motorized window treatment 610 is operable put the RF transceiver to sleep for an RF sleep time period T.sub.SLP-RF that is much longer than the packet time period T.sub.PACKET (e.g., approximately 17.3 msec) and to enable an RF transceiver for the RF sample time period T.sub.SMPL-RF that is much shorter than the packet time period T.sub.PACKET (e.g., approximately 5 msec) so as to conserve battery power. The motorized window treatments 610 execute an RF signal receiving procedure similar to the RF signal receiving procedure 300 of the second embodiment as shown in FIG. 9. However, the motorized window treatments 610 of the second embodiment do not put the RF transceiver to sleep for the snooze time period T.sub.SNOOZE after detecting an RF signal during the RF sample time period T.sub.SMPL-RF. Rather, the motorized window treatments 610 of the second embodiment simply remain on after detecting an RF signal during the RF sample time period T.sub.SMPL-RF.

(58) As shown in FIG. 12, the load control system 600 also comprises a lighting control device, e.g., a wall-mountable dimmer switch 630, which is coupled to an alternating-current (AC) power source 604 via a line voltage wiring 605. The dimmer switch 630 is operable to adjust the amount of power delivered to a lighting load 632 to control the lighting intensity of the lighting load. The dimmer switch 630 is operable to transmit and receive digital messages via the RF signals 606 and is operable to adjust the lighting intensity of the lighting load 632 in response to the digital messages received via the RF signals.

(59) FIG. 13 is a simplified block diagram of the dimmer switch 630 according to the second embodiment of the present invention. The dimmer switch 630 comprises a hot terminal H that is adapted to be coupled to the AC power source 604 and a dimmed hot terminal DH adapted to be coupled to the lighting load 632. The dimmer switch 630 comprises a controllably conductive device 710 coupled in series electrical connection between the AC power source 1002 and the lighting load 632 for control of the power delivered to the lighting load. The controllably conductive device 710 may comprise any suitable type of bidirectional semiconductor switch, such as, for example, a triac, a field-effect transistor (FET) in a rectifier bridge, or two FETs in anti-series connection. The dimmer switch 630 comprises a controller 714 that is operatively coupled to a control input of the controllably conductive device 710 via a gate drive circuit 712 for rendering the controllably conductive device conductive or non-conductive to thus control the amount of power delivered to the lighting load 632. The controller 714 is, for example, a microprocessor, but may alternatively be any suitable processing device, such as a programmable logic device (PLD), a microcontroller, or an application specific integrated circuit (ASIC).

(60) The controller 714 receives inputs from actuators 1116 for controlling the present intensity of the lighting load 632, and individually controls one or more visual indicators 718 for providing feedback of the present intensity of the lighting load. The controller 714 receives a control signal representative of the zero-crossing points of the AC mains line voltage of the AC power source 604 from a zero-crossing detector 720. The controller 714 is operable to render the controllably conductive device 710 conductive and non-conductive at predetermined times relative to the zero-crossing points of the AC waveform using a phase-control dimming technique. The dimmer switch 630 further comprises a memory 722 for storing the present intensity of the lighting load 632 as well as other operating characteristics of the dimmer switch. The memory 722 may be implemented as an external integrated circuit (IC) or as an internal circuit of the controller 714.

(61) The dimmer switch 630 also comprises a radio-frequency (RF) transceiver 724 and an antenna 726 for transmitting and receiving digital messages via RF signals. The controller 714 is operable to control the controllably conductive device 710 to adjust the intensity of the lighting load 632 in response to the digital messages received via the RF signals. The controller 714 may also transmit feedback information regarding the amount of power being delivered to the lighting load 632 via the digital messages included in the RF signals. The RF transceiver 724 could alternatively be implemented as an RF receiver for only receiving RF signals. To check for RF signals that are being transmitted, the controller 714 enables the RF transceiver 724 at a sampling period T.sub.SAMPLE (e.g., approximately 17.8 msec) using, for example, a duty cycle of approximately 50%, such that the dimmer switch 630 enables the RF transceiver for an RF sample time period T.sub.SMPL-RF (e.g., approximately 8.9 msec), and puts the RF transceiver to sleep for an RF sleep time period T.sub.SLP-RF (e.g., approximately 8.9 msec). Accordingly, the RF sleep time period T.sub.SLP-RF used by the dimmer switch 630 is longer than the packet time period T.sub.PACKET so as to reduce the total power consumed by the dimmer switch 630.

(62) The dimmer switch 630 comprises a power supply 728 for generating a direct-current (DC) supply voltage V.sub.CC for powering the controller 714, the memory 722, the RF transceiver 724, and the other low-voltage circuitry of the dimmer switch. Since the dimmer switch 630 does not have a connection to the neutral side of the AC power source 604, the power supply 724 is operable to conduct a charging current through the lighting load 632 to generate the DC supply voltage V.sub.CC. Some lighting loads 1004 may be susceptible to flickering and other undesirable behavior if the magnitude of the charging current conducted through the lighting load is too large. Accordingly, the use of the RF sleep time period T.sub.SLP-RF that is longer than the packet time period T.sub.PACKET by the controller 714 helps to reduce the magnitude of the charging current conducted through the lighting load 632 and thus helps to avoid flickering in the lighting load.

(63) FIG. 14 is a simplified block diagram of a dimmer switch 630′ according to an alternate embodiment of the present invention. The dimmer switch 630′ is very similar to the dimmer switch 630 of the second embodiment. However, the dimmer switch 630′ has an earth ground terminal GND that is adapted to be coupled to earth ground. The zero-crossing detector 620 and the power supply 628 of the dimmer switch 630′ are coupled between the hot terminal H and the earth ground terminal GND (rather than the dimmed hot terminal DH). Accordingly, the power supply 728 conducts the charging current through the earth ground terminal GND (rather than the lighting load 632). The magnitude of the total current conducted through the earth ground terminal GND by the dimmer switch 630′ is limited by standards and regulations in most countries. The use of the RF sleep time period T.sub.SLP-RF that is longer than the packet time period T.sub.PACKET by the controller 714 helps to reduce the magnitude of the charging current conducted through the earth ground terminal GND.

(64) Referring back to FIG. 12, the load control system 600 further comprises a wall-mounted button keypad 640 and a battery-powered tabletop button keypad 642. The wall-mounted button keypad 640 is powered from the AC power source 604 via the line voltage wiring 605, and the tabletop button keypad 642 is a battery-powered device. Both of the keypads 640, 642 transmit digital messages to the dimmer switch 630 via the RF signals 606 in order to provide for remote control of the lighting load 632. In addition, each of the keypads 640, 642 is operable to receive digital status messages via the RF signals 606 from the dimmer switch 630 in order to display the status (i.e., on/off state and/or intensity level) of the lighting load 632. The load control system 600 further comprises a battery-powered remote control 644 which is operable to transmit digital messages to the dimmer switch 630 via the RF signals 606 in order to provide for remote control of the lighting load 632. The wall-mounted button keypad 640, the tabletop button keypad 642, and the remote control 644 are also operable to adjust the present position P.sub.PRES of the battery-powered motorized window treatments 610 by transmitting digital messages via the RF signals 606. In addition, the battery-powered motorized window treatments 610 may be operable to transmit status information to the wall-mounted keypad 640 and tabletop button keypad 642.

(65) The load control system 600 further comprises a battery-powered wireless occupancy sensor 646 for detecting an occupancy condition (i.e., the presence of an occupant) or a vacancy condition (i.e., the absence of an occupant) in the space in which the occupancy sensor is mounted. The occupancy sensor 646 is operable to wirelessly transmit digital messages via the RF signals 606 to the dimmer switch 630 in response to detecting the occupancy condition or the vacancy condition in the space. For example, in response to detecting an occupancy condition in the space, the occupancy sensor 646 may transmit a digital message to the dimmer switch 630 to cause the dimmer switch to turn on the lighting load 632, and in response to detecting a vacancy condition in the space, transmit a digital message to the dimmer switch to cause the dimmer switch to turn off the lighting load. Alternatively, the occupancy sensor 646 could be implemented as a vacancy sensor, such that the dimmer switch 630 would only operate to turn off the lighting load 632 in response to receiving the vacant commands from the vacancy sensor. Examples of RF load control systems having occupancy and vacancy sensors are described in greater detail in commonly-assigned U.S. Pat. No. 7,940,167, issued May 10, 2011, entitled BATTERY-POWERED OCCUPANCY SENSOR; U.S. Pat. No. 8,009,042, issued Aug. 30, 2011, entitled RADIO-FREQUENCY LIGHTING CONTROL SYSTEM WITH OCCUPANCY SENSING; and U.S. patent application Ser. No. 12/371,027, filed Feb. 13, 2009, entitled METHOD AND APPARATUS FOR CONFIGURING A WIRELESS SENSOR; the entire disclosures of which are hereby incorporated by reference.

(66) The load control system 600 further comprises a battery-powered daylight sensor 648 for measuring an ambient light intensity in the space in which the daylight sensor in mounted. The daylight sensor 648 wirelessly transmits digital messages via the RF signals 606 to the dimmer switch 630. For example, the daylight sensor 648 may transmit a digital message to the dimmer switch 630 to cause the dimmer switches to increase the intensities of the lighting load 632 if the ambient light intensity detected by the daylight sensor 648 is less than a setpoint light intensity, and to decrease the intensities of the lighting load if the ambient light intensity is greater than the setpoint light intensity. The packet break time period T.sub.PKT_BRK of the packets transmitted by the daylight sensor 648 may be variable, for example, as a function of the measured light intensity. The battery-powered motorized window treatments 610 may be operable to receive digital messages from the occupancy sensor 646 and the daylight sensor 648 via the RF signals 606 and to adjust the present position of the window treatments. Examples of RF load control systems having daylight sensors are described in greater detail in commonly-assigned U.S. patent application Ser. No. 12/727,956, filed Mar. 19, 2010, entitled WIRELESS BATTERY-POWERED DAYLIGHT SENSOR, and U.S. patent application Ser. No. 12/727,923, filed Mar. 19, 2010, entitled METHOD OF CALIBRATING A DAYLIGHT SENSOR, the entire disclosures of which are hereby incorporated by reference.

(67) The load control system 600 further comprises a battery-powered temperature control device 650 (e.g., a thermostat) that is operable to control a heating and/or cooling system, e.g., a heating, ventilation, and air conditioning (HVAC) system 652. The temperature control device 650 may be coupled to the HVAC system 652 via an HVAC communication link 654, e.g., a digital communication link (such as an RS-485 link, an Ethernet link, or a BACnet® link), or alternatively via a wireless communication link (such as an RF communication link). The temperature control device 650 may comprise an internal temperature sensor for determining a present temperature in the space in which the temperature control device is located. The temperature control device 650 transmits appropriate digital messages to the HVAC system 652 to control the present temperature in the building towards a setpoint temperature. Alternatively, the HVAC communication link 654 could comprise a more traditional analog control link for simply turning the HVAC system 652 on and off. The temperature control device 650 comprises a user interface, e.g., a touch screen 656, for displaying the present temperature and the setpoint temperature, and for receiving user inputs for adjusting the setpoint temperature. The temperature control device 650 is operable to receive RF signals 606 from a wireless temperature sensor 656 for determining the present temperature in the space, for example, at a location away from the temperature control device 650. In addition, the motor drive units 620 of each of the motorized window treatments 610 may be operable to transmit the temperature measurements from the internal and/or external temperature sensors 160, 162 to the temperature control device 650.

(68) Each of the battery-powered devices of the load control system 600 (i.e., the tabletop button keypad 642, the remote control 644, the occupancy sensor 646, the daylight sensor 648, and the temperature control device 650) is operable to enable their respective RF transceivers at a sampling period T.sub.SAMPLE (e.g., approximately 17.8 msec) to detect if an RF signal 602 is presently being transmitted as described above for the motorized window treatments 610. Each of these battery-powered devices is operable put its RF transceiver to sleep for an RF sleep time period T.sub.SLP-RF that is much longer than the packet time period T.sub.PACKET (e.g., approximately 5 msec) and to enable the RF transceiver for the RF sample time period T.sub.SMPL-RF that is much shorter than the packet time period T.sub.PACKET (e.g., approximately 17.3 msec) so as to conserve battery power.

(69) In addition, the load control system 600 could also comprise other types of input devices and load control devices that each may put its RF transceiver to sleep for an RF sleep time period T.sub.SLP-RF that is much longer than the packet time period T.sub.PACKET. For example, the additional types of input devices may comprise battery-powered remote controls, a temperature sensors, humidity sensors, security sensors, proximity sensors, keypads, key fobs, cell phones, smart phones, tablets, personal digital assistants, personal computers, timeclocks, audio-visual controls, safety devices, and central control transmitters. The additional types of load control devices may comprise, for example, an electronic dimming ballast for a fluorescent lamp; a driver for a light-emitting diode (LED) light source; a screw-in luminaire that includes a light source and an integral load regulation circuit; a switching device for turning one or more appliances on and off; a plug-in load control device for controlling one or more plug-in loads; a motor control device for controlling a motor load, such as a ceiling fan or an exhaust fan.

(70) The load control system 600 further comprises signal repeaters 660A, 660B, which are operable to retransmit any received digital messages to ensure that all of the control devices of the load control system receive all of the RF signals 606. The load control system 600 may comprise, for example, one to five signal repeaters depending upon the physical size of the system. Each of the control devices, (e.g., the motorized window treatments 610, the dimmer switch 630, the tabletop button keypad 642, the wall-mounted button keypad 640, the occupancy sensor 646, the daylight sensor 648, and the temperature control device 650) of the load control system 600 are located within the communication range of at least one of the signal repeaters 660A, 660B. The signal repeaters 660A, 660B are powered by the AC power source 604 via power supplies 662 plugged into electrical outlets 664.

(71) According to the third embodiment of the present invention, one of the signal repeaters (e.g., signal repeater 660A) operates as a “main” repeater (i.e., a main controller) to facilitate the operation of the load control system 600. The main repeater 660A has a database, which defines the operation of the load control system, stored in memory. For example, the main repeater 660A is operable to determine which of the lighting load 632 is energized and to use the database to control any visual indicators of the dimmer switch 630 and the keypads 642, 640 accordingly to provide the appropriate feedback to the user of the load control system 600. In addition, the control devices of the load control system may be operable to transmit status information to the signal repeaters 660A, 660B. For example, the motor drive unit 620 of each of the motorized window treatments 610 may be operable to transmit a digital message representative of the magnitude of the respective battery voltage to the signal repeaters 660A, 660B, a digital message including a low-battery indication to the signal repeaters when operating in the low-battery mode, or a digital message including a representation of the present position P.sub.PRES of the motorized window treatment.

(72) As mentioned above, the load control system 600 may comprise one to five signal repeaters depending upon the physical size of the system. The control devices of the load control system 600 are each operable to adjust the RF sampling period T.sub.SAMPLE in response to the total number N.sub.RPTR of signal repeaters within the load control system 600. Specifically, each control device is operable to adjust the RF sleep time period T.sub.SLP-RF, while keeping the RF sampling time period T.sub.SMPL-RF constant. The control devices adjust the respective sampling periods because packets of data may be transmitted differently via the RF signals 606 depending on the number of repeaters in the load control system 600. In particular, the packet break time period T.sub.PKT_BRK of the data transmissions may vary in response to the number of repeaters to ensure that the signal repeaters in the load control system 600 have sufficient time to propagate a given packet. Because the packet break time period T.sub.PKT_BRK is a factor in appropriately sizing the RF sleep time period T.sub.RF_SLEEP of each of the control devices to ensure that an RF sampling event coincides with a packet transmission as discussed above with respect to FIG. 8, the RF sleep time period T.sub.RF_SLEEP also varies accordingly if the packet break time period T.sub.PKT_BRK of a transmitted packet varies.

(73) FIG. 15 is a simplified flowchart of an RF sampling rate selection procedure 800 that may be executed by any of control devices of the load control system 600, e.g., the motor drive unit 620. Typically, this sampling rate procedure 800 may be executed during a configuration of the motor drive unit 612. In the event that there is at least one signal repeater (e.g., signal repeater 660A) in the load control system 600, that signal repeater will send a message to the motor drive unit 620 to inform the motor drive unit of the total number of repeaters N.sub.RPTR in the load control system. At step 810, the motor drive unit 620 determines whether it has received a packet containing the number of repeaters N.sub.RPTR. In the event that the motor drive unit 620 has not received such a packet, then the motor drive unit assumes that it is operating in a load control system that contains no signal repeaters. As a result, the motor drive unit 620 uses a first RF sleep time period value T.sub.SLP-RF1 (e.g., approximately 17.8 msec) as the RF sleep time period T.sub.SLP-RF at step 812 before the RF sampling rate selection procedure 1100 exits.

(74) If the motor drive unit 620 has received a packet containing the number of repeaters N.sub.RPTR, the motor drive unit determines whether the number of repeaters N.sub.RPTR is greater than three at step 814. If the number of repeaters N.sub.RPTR is not greater than three at step 814, the motor drive unit 620 uses the first RF sleep time period value T.sub.SLP-RF1 (e.g., approximately 17.8 msec) as the RF sleep time period T.sub.SLP-RF at step 816 before the sampling rate selection procedure 800 exits. If the number of repeaters N.sub.RPTR is greater than three at step 814, the motor drive unit 620 uses a second RF sleep time period value T.sub.SLP-RF2 (e.g., approximately 16.3 msec) as the RF sleep time period T.sub.SLP-RF at step 818 before the RF sampling rate selection procedure 800 exits. The RF sampling rate selection procedure 800 ensures that the motor drive unit 620 adjusts its RF sampling rate T.sub.SAMPLE in response to the number of repeaters in the load control system 600 to optimize reliability, response time, and battery life. The other battery-powered devices of the load control system 600 (i.e., the tabletop button keypad 642, the remote control 644, the occupancy sensor 646, the daylight sensor 648, and the temperature control device 650) may also execute the RF sampling rate selection procedure 800.

(75) The RF transceivers of the control devices of the load control system 600 are characterized by a signal strength threshold which is used to detect the transmitted RF signals 606. Particularly, the RF transceiver of each of the control devices of the load control system 600 is characterized by an adjustable signal strength threshold. FIG. 16 is a simplified graph illustrating various signal strength thresholds of, for example, the RF transceiver of one of the motor drive units 620. In particular, FIG. 16 illustrates two signal strength thresholds of the RF transceiver: a first threshold 860 (i.e., an extended battery threshold) and a second threshold 870 (i.e., an extended range threshold) having a lower magnitude than the first threshold. The first and second thresholds 860, 870 reside between a noise floor 880 and a signal strength 850 of the nearest signal repeater (e.g., one of the signal repeaters 660A, 660B). While FIG. 16 is described with reference to the motorized window treatments 620, the other battery-powered devices of the load control system 600 (i.e., the tabletop button keypad 642, the remote control 644, the occupancy sensor 646, the daylight sensor 648, and the temperature control device 650) may also have RF transceivers having adjustable signal strength thresholds.

(76) During a configuration or set-up procedure of each of the motor drive units 620, a user may be operable to select the signal strength of the RF transceiver as having either the first threshold 860 or the second threshold 870. When using the second threshold 870 to detect RF signals 606, the RF transceiver is operable to detect RF signals of a lower signal strength which can improve the range performance of the RF transceiver (i.e., the RF transceiver can detect RF signals sent from control devices that are located farther away). However, the second threshold 870 may cause the RF transceiver to be more sensitive to noise events as the noise floor 880 may occasionally exceed the second threshold. Each time the RF transceiver receives any RF energy (RF signals 606, RF noise, etc.) that exceeds the second threshold 870 during the RF sampling time period T.sub.SMPL-RF, the RF transceiver wakes up the controller of the motor drive unit 620, such that the controller then consumes additional power which ultimately reduces the life of the batteries of the motor drive unit. When the RF transceiver uses the first threshold 860 to detect RF signals 606, the RF transceiver is less likely to detect RF signals having a lower signal strength, but is less susceptible to noise events. Because the RF transceiver only responds to RF energy (RF signals 606, RF noise, etc) that exceeds the first threshold 860, the RF transceiver does not wake up the controller as frequently as when the second threshold 870 is used. As a result, the life of the batteries can be further extended when the RF transceiver uses the first threshold 660.

(77) The first and second thresholds 860, 870 may be predetermined values. For example, the first threshold 860 may have a value of approximately −90 dBm and the second threshold 670 may have a value of approximately −97 dBm. Alternatively, the value of the adjustable threshold of the RF transceiver could be determined automatically during the configuration procedure of the motor drive unit 620. For example, the RF transceiver may be operable to detect an average magnitude of the noise floor 880 and may also be able to detect a magnitude of the signal strength 850 of the nearest signal repeater 660A, 660B, and then provide these magnitudes to the controller of the motor drive unit. The controller may then calculate an optimal value of a threshold for the RF transceiver that will preserve battery life and provide appropriate range performance. For example, the controller may halve the sum of the magnitude of the noise floor 880 and the magnitude of the signal strength 850 of the nearest signal repeater to calculate the value of the threshold for the RF transceiver. In addition, in the event that the calculated threshold value of the RF transceiver is too close (e.g., within ˜5 dBm) to the noise floor 880, the load control system 600 may be operable to prompt a user, e.g., through a programming interface (not shown), to add another signal repeater to the system. By adding another signal repeater to the system, the magnitude of the signal strength of the nearest signal repeater may increase, thus increasing the calculated threshold of the RF transceiver. As a result, the battery life of each of the motor drive units 620 may be further extended.

(78) During the configuration process of the load control system 600, the motor drive units 620 are each assigned to a particular frequency channel such that each motor drive can receive RF signals 606 transmitted on that frequency channel. During normal operation, the motor drive units 620 will each detect any packet of information that is transmitted on the respective assigned frequency channel—even if that packet does not contain data that is addressed to the motor drive unit. As soon as the RF transceiver of each motor drive unit 620 begins to detect a packet transmitted on the assigned frequency channel, the RF transceiver will wake up the controller of the motor drive unit as previously described. The controller will then process the packet to determine whether it must adjust the present position P.sub.PRES of the motorized window treatment 610. In the event that the packet is not addressed to the motor drive unit 620 (e.g., the packet contains information only for a dimmer switch 630), the controller will take no further action and will go back to sleep. However, because the controller woke up to process the packet, the controller consumed power unnecessarily, and negatively impacted the life of the batteries of the motor drive unit 620.

(79) Because the load control system 600 comprises many devices that are operable to send and/or receive RF signals 606, there can be a very large number of packets regularly transmitted within the system. Many of these packets may not be addressed to the motor drive units 620, and as a result, need not be processed by the controller of each of the motor drive units. According to an aspect of the present invention, the battery-power motorized window treatments 610 may be configured to only listen to RF signals 606 transmitted on an alternate channel distinct from the channels used by the other devices of the load control system 600.

(80) FIG. 17 is a simplified flowchart of an RF monitoring procedure 900 performed by a main repeater (e.g., the signal repeater 660A) of the load control system 600. At step 910, the main repeater 660A configures all of the control devices of the load control system 600 to use a given frequency channel (e.g., frequency channel A). At step 912, the main repeater 660A is operable to monitor a number N of RF packets transmitted within a given time frame during normal operation. At step 914, the main repeater 660A compares the number N of RF packets to a predetermined maximum number N.sub.MAX to determine whether the load control system 600 has a high amount of traffic on frequency channel A. If the number N of RF packets is greater than the predetermined maximum number N.sub.MAX at step 914, the main repeater 660A configures all of the battery-powered motorized window treatments 610 to listen only to an alternate frequency channel (e.g., frequency channel B). Otherwise, the main repeater 660A simply exits the RF monitoring procedure 900 without changing the channel configuration of the battery-powered motorized window treatments 610. Alternatively, the main repeater 660A could simply configure all battery-powered motorized window treatments 610 to use the alternate frequency channel (i.e., frequency channel B) in lieu of executing the RF monitoring procedure 900.

(81) FIG. 18 is a simplified flowchart of an RF signal receiving procedure 1000 performed by the signal repeaters (e.g., the signal repeater 660A) of the load control system 600 during normal operation when an alternate frequency is in use. At step 1010, the signal repeater 660A receives a packet transmitted on frequency channel A. At step 1012, the signal repeater 660A determines whether the received packet is addressed to at least one of the battery-powered motorized window treatments 610. If the packet is not addressed to any of the battery-powered motorized window treatments 610 (e.g., the packet is addressed to the dimmer switch 630), then the repeater 660A simply retransmits the packet on channel A at step 1014 before the RF signal receiving procedure 1000 exits. However, if the signal repeater 660A determines that the received packet is addressed to at least one of the battery-powered motorized window treatments 610, the signal repeater changes its frequency channel from channel A to channel B at step 1016 and transmits the received packet on frequency channel B to the battery-powered motorized window treatments 610 at step 1018. Finally, the signal repeater 660A changes its frequency channel from channel B back to channel A at step 1020 and the RF signal receiving procedure 1020 exits.

(82) FIG. 19 is a simplified diagram of a RF load control system 1100 having two signal repeaters 1160A, 1160B coupled together via a digital communication link 1166 according to a third embodiment of the present invention. The first signal repeater 1160A is configured to transmit and receive packets via the RF signals 606 using only the primary frequency channel A, and the second signal repeater 1160B is configured to transmit and receive packets via the RF signals 606 using only the alternate frequency channel B. The first and second signal repeaters 1160A, 1160B are operable to transmit digital messages to each other via the digital communication link 1166, which may comprise, for example, a wired communication link, such as an RS-485 link or an Ethernet link, link, or alternatively may comprise a wireless communication link, such as an RF communication link.

(83) In the event that the first signal repeater 1160A receives an packet that is transmitted on channel A and is addressed to at least one of the battery-powered motorized window treatments 610, the signal repeater 1160A transmits a digital message (e.g., including the data from the packet) to the second signal repeater 1160B via the digital communication link 1166. Upon receiving the information via the digital communication link 1160B, the second signal repeater 1160B transmits the packets to the battery-powered motorized window treatments 610 via the RF signals 606 using the alternate frequency B. The packets transmitted to the motorized window treatments 610 by the second signal repeater 1160B include the same (or similar) data as the packets that were received by the first signal repeater 1160A. Thus, the battery-powered motorized window treatments 610 only listen to RF signals 606 transmitted on the alternate frequency channel B distinct from the channel used by the other devices of the load control system 600 in order to further preserve the battery life of the battery-powered window treatments.

(84) Examples of battery-powered remote controls and RF control systems are described in greater detail in commonly-assigned U.S. patent application Ser. No. 12/399,126, filed Mar. 6, 2009, entitled WIRELESS BATTERY-POWERED REMOTE CONTROL HAVING MULTIPLE MOUNTING MEANS; U.S. Pat. No. 7,573,208, issued Aug. 22, 2009, entitled METHOD OF PROGRAMMING A LIGHTING PRESET FROM A RADIO-FREQUENCY REMOTE CONTROL, and U.S. patent application Ser. No. 12/033,223, filed Feb. 19, 2008, entitled COMMUNICATION PROTOCOL FOR A RADIO-FREQUENCY LOAD CONTROL SYSTEM, the entire disclosures of which are hereby incorporated by reference.

(85) Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.