Abstract:
A wireless battery-operated window covering assembly is disclosed. The window covering has a head rail in which all the components are housed. These include a battery pack, an interface module including an IR receiver and a manual switch, a processor board including control circuitry, motor, drive gear, and a rotatably mounted reel on which lift cords wind and unwind a collapsible shade. The circuitry allows for dual-mode IR receiver operation and a multi-sensor polling scheme, both of which are configured to prolong battery life. Included among these sensors is a lift cord detector which gauges shade status to control the raising and lowering of the shade, and a rotation sensor which, in conjunction with internal registers and counters keeps track of travel limits and shade position.

Description:
RELATED APPLICATIONS 
     This is a continuation of U.S. Ser. No. 09/357,761, filed Jul. 21, 1999, now U.S. Pat. No. 6,057,658, which is a continuation of U.S. Ser. No. 09/131,417, filed Aug. 10, 1998, now U.S. Pat. No. 5,990,646, which is a continuation of Ser. No. 08/757,559, filed Nov. 27, 1996, now U.S. Pat. No. 5,793,174, which claims priority to provisional application No. 60/025,541, filed Sep. 6, 1996. 
    
    
     TECHNICAL FIELD 
     This invention relates to electrically powered window coverings such as vertically adjustable shades, tiltable blinds and the like. More particularly, the invention relates to motorized window coverings which are activated by a wireless remote control transmitter and have associated with them a DC motor and electrical and mechanical circuitry adapted to store position information. 
     BACKGROUND 
     Wireless, remote control, motorized window coverings are activated by a control signal generated and sent by a transmitter. As explained in U.S. Pat. No. 4,712,104 to Kobayashi, the control signal is usually converted into one of audio, radio (RF), or light (either visible or, more preferably, infrared (IR)) energy, and transmitted through the air. When a button on a remote transmitter is pushed, the control signal comprising one of these types of energy is generated. The control signal sent by the transmitter may comprise a carrier signal which modulates either a continuous waveform or, more preferably, a sequence of spaced apart pulses. In those cases where spaced apart pulses are used, the pulses may either be coded, or they may comprise a sequence of pulses having substantially identical pulse widths and a constant pulse repetition frequency (PRF). 
     Each wireless, remote control motorized window covering system is provided with at least one transducer which converts the transmitted energy into electrical signals. In the case of an audio signal, the transducer is a microphone. In the case of RF signal, the transducer is likely to be an antenna, which may comprise an electromagnetic coil tuned to the carrier frequency. Finally, in the case of a light signal, the transducer is typically a photodiode, a photoresistor or a phototransistor. 
     As the signal travels from the transmitter to the transducer, it may become slightly corrupted. For instance, in the case of an acoustic signal, environmental noise in frequencies of interest, may be added to the signal. In the case of a light signal, light from other sources may be added to the received signal. Further corruption may take place as the transmitted signal is converted by the transducer into an electrical signal. This is because all transducers, however precise, cannot output an electrical signal which perfectly replicates the incoming transmitted signal. Usually, the electrical signal from the transducer will vary slightly from what was transmitted. 
     In addition to being corrupted, the signal may have also been modulated before transmission, as explained above. Together, these factors result in a signal that is distorted, and may be unintelligible to a decision circuit, described further below. To help correct some of this distortion, the electrical signal from the transducer is usually preprocessed before it is interpreted by a decision circuit. The goal of this preprocessing is to convert the electrical signal from the transducer to a form that can be used, and is less likely to be mis-interpreted, by the decision circuit. This process is loosely referred to as “cleaning up” the signal. 
     Cleaning up a signal from a transducer may involve filtering and demodulating a signal, as is often necessary with RF and IR signals. It may also involve waveshaping using comparators, inverters and triggers which have hysteresis-like input/output relationships, as disclosed in U.S. Pat. No. 5,275,219 and Canadian Patent No. 1,173,935 to Yamada, both of which are directed to motorized window systems which respond to daylight. In the case of IR signals, an integrated IR receiver, having a photodiode or a phototransistor, signal amplifiers, bandpass filters, demodulators, integrators and hysteresis-like comparators for waveshaping, perform such a function. The IS1U60, available from Sharp Electronics, is such a receiver, and can be used in remote control operations. 
     As stated above, in a remote control system, the cleaned up control signal is presented to a decision circuit. The role of the decision circuit is to determine a) whether the cleaned up control signal is valid, i.e., whether or not the signal content is such that the system should respond, and b) what, if any, response should be taken, in view of the control signal content and other status information. 
     The decision circuit comprises additional sensors, switches and registers, which keep track of such things as the direction of last motion, the position of the window covering relative to its travel extremes, and other status information. The decision circuit may be formed entirely from a combination of discrete analog and digital components, in which case the decision circuit is said to be hardwired. Alternatively, the decision circuit may include a microprocessor, microcontroller, or equivalent, in which case the decision circuit is said to be programmable. As is known to those skilled in the art, incorporating a microprocessor, or the like, allows for more complex decision making with the control signals and other status information. 
     All decision making circuits, whether or not they incorporate a microprocessor, are connected to a motor circuit adapted to drive a DC motor. Although the exact implementation of a motor circuit may differ, they all serve to connect the source of power, be it a battery, a solar cell, or even an AC-to-DC transformer, to the motor to operate the window covering. A typical motor circuit is disclosed in U.S. Pat. No. 4,618,804 to Iwasaki. In this circuit, two signals from the drive circuit are used to activate a pair of transistors. In such a motor circuit, upon receipt of an “UP” motor signal from the decision circuit, current flows from the voltage source, through a first transistor, the motor, and a second transistor to drive the motor in a first direction (e.g., clockwise). And, upon receipt of a “DOWN” motor signal, current flows from the voltage source through a third transistor, the motor, and a fourth transistor to drive the motor in an opposite direction (e.g., counterclockwise). 
     The power supply for a motorized window covering system may originate from an alternating current (AC) source, as shown in U.S. Pat. No. 3,809,143 to Ipekgil. In such case, one plugs into a wall socket and a transformer, or the like, is used to convert the AC into DC. As an alternative to using an AC power source, the power supply may comprise a battery, which may be recharged by a solar cell and/or by plugging into an AC source. U.S. Pat. No. 4,664,169 to Osaka discloses such a battery-operated lift system which moves a bottommost supporting slat relative to a headrail. 
     In wireless, remote-controlled motorized systems having an AC power source, there is little concern about designing the system to minimize energy consumption. This is because the AC source provides, for all practical purposes, virtually unlimited power. On the other hand, when a battery, especially one that cannot be recharged, is used, the current draw of the system becomes a design concern. This is because the transducer must always be available to receive a transmitted control signal. Also, the preprocessing, decision making and motor drive circuitry must be prepared to respond immediately, which usually means that they are, at the very least, in a “standby mode”, which also draws at least some current. 
     In the case of battery powered systems, there are three general approaches to conserving battery power. One approach is to use low-power, discrete analog and digital components which are on at all times, whether or not a valid control signal is received. This is the approach taken in U.S. Pat. No. 5,495,153 to Domel et al., which calls for using low dark-current phototransistors, and low-power logic devices such as NAND gates, counters, flip flops, power saving resistors, and the like. A second approach is to cycle one or more components on and off while waiting for a valid signal. This is the approach taken in U.S. Pat. No. 5,134,347 to Koleda, which calls for turning an IR receiver on for a brief period of time, and then allowing it continue to stay on longer if it receives a valid signal. The approach taken in Koleda is based on well-settled techniques for reducing the duty cycle of a receiver powered by a battery, as disclosed in U.S. Pat. No. 4,101,873 to Anderson et al. Finally, the third approach of conserving battery power is to use a solar cell to continuously recharge the batteries. U.S. Pat. No. 4,644,990 to Webb discloses a photosensitive energy conversion element which recharges batteries used to supply power to automatic system for tilting blinds. 
     To operate a window covering, the motor is typically placed in a headrail where it is hidden from view. A rod, to which the motor is operatively engaged, is rotatably mounted in the headrail. When the rod rotates, cords connected at one end to the rod, and also connected to the shade or blinds, can be wound either directly on the rod or on a spool arranged to turn with the rod in a lift system. U.S. Pat. No. 4,550,759 to Archer shows such a system for controlling the tilt of a blind, and U.S. Pat. No. 4,856,574 to Minami shows a motorized system for controlling the lift of a horizontal slat. 
     The extent of travel for a window covering can be limited by a counter, which uses dead reckoning to keep track of the number of rotations of the motor or the rod, relative to a stored counter value. In such case, the rotating wheel, or the like interrupts an optical or a magnetic path, and these interruptions are counted. Such systems are shown in the aforementioned Minami &#39;574 reference. 
     As an alternative to “dead reckoning”, limit switches may be used to control the extent of movement of the window covering. Limit switches are mechanical switches which are activated by engagement with a member of the system during the latter&#39;s operation. In the typical case, the limit switches are stationary and are abutted by a movable member of the motorized system. U.S. Pat. No. 4,727,918 to Schroeder discloses the use of limit switches in the headrail to control the tilt of a blind. Along similar lines, Danish patent No. 144,894 to Gross discloses the use of limit switches in the headrail to control the lift of a shade. 
     It should be noted here that we have used the word “shade” to generically describe a window covering which could be raised and lowered. This word encompasses such window coverings as venetian blinds comprising horizontal slats, pleated shades, accordion shades, and the like. As is known to those skilled in the art, pleated and accordion shades are typically formed from a lightweight fabric, and thus are often lighter than the more rigid slats. Because of this, it is generally accepted that mechanisms having sufficient torque to raise and lower horizontal slats, can also raise and lower lightweight shades. 
     Finally, in the typical remote control motorized system, the transducers, circuitry, motors, and servo mechanisms used to operate one type of window covering, can often be adapted to operate other types. For instance, as explained in International Publication WO 90/03060 to Roebuck, a motor/servo arrangement capable of opening and closing vertical slats and also drawing them, can readily be adapted to venetian blinds (horizontal slats) and the like. Similarly, EPO 381,643 to Archer shows that a DC motor mounted in headrail and connected to rotatably mounted rod can lift horizontal slats or pleated shades with virtually no modifications. 
     The prior art also includes systems which combine a large number of the features discussed above. For instance, there are wireless, remote-control lift systems having a headrail-mounted DC motor which winds a lift cord around a rod, and which has additional novel features. One such example is the battery-powered device of U.S. Pat. No. 5,029,428 to Hiraki, which is placed between the panes of a double-pane window. Another, is the IR-controlled, AC-powered, microprocessor-based device of Japanese Laid-open application 4-237790 to Minami, which provides for a programmable lower limit for the shade using the transmitter. 
     SUMMARY OF THE INVENTION 
     The present invention provides a battery-powered, wireless, remote-control, microprocessor-driven, motorized window covering assembly having the batteries, motor, drive gear, a rotatably mounted reel around which is lift cord is wound for raising and lowering a shade, circuitry and sensors, all housed in a headrail, making the resulting device more visually appealing. 
     One aspect of the invention is that the assembly&#39;s circuitry is configured to prolong the life of the batteries. In this regard, the IR receiver is alternately turned on and off in one of two power states which differ only in the length of the on-off power cycle. Peripheral sensors are also operated only on an as-needed basis, under microprocessor control to further prolong battery life. These sensors, along with flags, timers and registers controlled by the microprocessor, are arranged to restrict motor operation under inappropriate conditions, thereby both prolonging battery life and preventing damage to the assembly. 
     Another aspect of the present invention is that the assembly having a detector which engages the lift cord to determine when the shade has either been fully lowered, or alternatively, has met with an obstruction, the detector being used to control both the downward movement of the shade, and also the upper limit of shade travel, in conjunction with a remote control transmitter. 
     Yet another aspect of the present invention is a resilient, vibration dampening bushing which mounts the motor onto the head rail, thereby reducing vibrations transferred to the head rail and also to the rod. This not only helps dissipate energy imparted to the headrail, but also reduces annoying acoustic noise. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a window covering assembly in accordance with the present invention. 
     FIG. 2 is an end view of the assembly shown in FIG.  1 . 
     FIG. 3 is a top view of the head rail. 
     FIG. 4 is a partially foreshortened front view of the assembly. 
     FIG. 5 is a sectional view taken along line  5 — 5  in FIG.  3 . 
     FIG. 6 is a sectional view taken along line  6 — 6  in FIG.  3 . 
     FIG. 7 is a perspective view of the lift cord which engages the reed switch. 
     FIG. 8 is a perspective view of the assembly of FIG. 1, with the front panel raised. 
     FIG. 9 is an enlarged perspective view of the motor and transmission assembly and mounting therefor. 
     FIG. 10 is a side elevation view of the mounting bushing shown in FIG.  9 . 
     FIG. 11 is a front elevation view of the mounting bushing shown in FIG.  10 . 
     FIG. 12 is a perspective view of a drive rod including a counter wheel. 
     FIG. 13 is a block diagram of a control circuit utilized in the present invention. 
     FIG. 14 is a circuit diagram of the power supply of FIG.  13 . 
     FIG. 15 is a circuit diagram of the processor connections. 
     FIG. 16 is a circuit diagram of the interface module. 
     FIG. 17 is a circuit diagram of the sensor subcircuit. 
     FIG. 18 is a circuit diagram of the bridge circuit. 
     FIGS. 19,  19 A- 19 J present a flow chart illustrating the microprocessor controlled operation of the window covering shown in FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a window covering assembly  100  of the present invention. The assembly comprises a head rail  102 , a bottom rail  104 , and a shade  106 . Preferably, the head rail  102  and bottom rail are formed from aluminum, plastic, or some other light weight materials. The shade  106  shown FIG. 1 is an expandable and contractible covering preferably made from a light fabric, paper, or the like. The shade of FIG. 1 is shown to be a cellular honeycomb shade; however, a pleated shade, horizontal slats, and other liftable coverings can also be used. 
     As seen in FIGS. 1 and 2, the head rail  102  comprises a bottom panel  108 , a back panel  110 , end caps  112  and a front panel  114 . The front panel  114  is hinged by pins, attached at its upper end corners, to the end caps  112 . This facilitates access to the cavity  116  within the head rail  102  behind the front panel&#39;s front surface  118 . Alternatively, the front panel  114  can be hinged to the bottom member  108 , or even be fully removable and snapped on to the rest of the head rail. 
     A plurality of lift cords  120  descend from within the head rail  102 , pass through the cells of the honeycomb shade  106 , to the bottom rail where they are secured by known means. The weight of the bottom rail  104  and shade  106  are supported by the lift cords  120 , causing the latter to normally undergo tension. 
     FIG. 3 shows a top view of the cavity  116 . Within the cavity  116  are an elongated tube  150  forming a battery pack which houses batteries  152  and is mounted on the cavity-facing side of the front panel  118 . The tube  150  is preferably formed from a non-conductive material such as plastic. Also mounted in the cavity is a motor  122  operatively engaged to a rotatably mounted reel shaft  124 , around which reel shaft the lift cords  120  are wound and unwound. Preferably, the reel shaft is hollow to reduce its weight. This reduces the torque and power requirements, thus extending battery life. A printed circuit (PC-) board  126  which carries much of the electronic circuitry of the assembly is also housed in the cavity. 
     As best seen in FIGS. 3 and 4, an interface module  128  communicates between the front surface  118  and the cavity  116 . The interface module  128  comprises an infrared (IR) receiver and a manual switch  130 . On the front surface  118 , the manual switch  130  and a daylight-blocking window  132  are visible. The manual switch  130  can be activated by a user at any time. The window  132  covers the photoreceiver (i.e., transducer) of the IR receiver and helps extend the life of the batteries by preventing daylight from needlessly activating the transducer. One skilled in the art would recognize that an IR receiver, whose transducer has a built-in daylight-blocking window or a daylight-blocking coating, may also be used. The important thing is that the transducer not respond to daylight, and preferably be arranged such that it only responds to infrared light. It should be noted that the shade has no manually operated pull cord. Thus, the manual switch  130  on the front panel, and the IR receiver are normally the only means for operating the window covering. 
     As shown in FIG. 6, the motor  122  and its transmission  134  are operatively connected to a drive rod  136  having a square cross-section. The drive rod  136  is received by a telescoping reel shaft  124  which turns in spaced-apart bearings  138 , each integrally formed with a reel support  140 . When the drive rod  136  turns, the reel shaft  124  turns and also telescopes in an axial direction, one rotation of the reel shaft corresponding to an axial movement approximately equal to the thickness of the lift cord  120 ′. Thus, the lift cord passes through the bottom plate of the head rail at substantially the same position as it winds and unwinds. Thus, as seen in FIG. 6, the lift cord  120 ′ is wrapped around the reel shaft  124 , each turn abutting its neighbor without overlap, and its end  142  secured to the reel shaft by a ring-shaped clamp  144 . 
     FIG. 7 illustrates the significance of having a particular lift cord  120 ′ pass through the bottom panel  108  at the same position, as it winds and unwinds. A lift cord detector  146 , formed as a reed switch, is mounted on the inside surface of the bottom panel  108 . The lift cord detector  146  is positioned such that the lift cord  120 ′ abuts the detector&#39;s reed  148 , when there is tension in the lift cord  120 ′. When it abuts the reed  148 , the lift cord  120 ′ closes a connection in the switch. In the present design, the detector&#39;s reed  148  must be in abutment with the cord  120 ′ for the motor  122  to lower the shade. 
     There are two situations of interest in which the detector&#39;s reed  148  no longer abuts the lift cord  120 ′ during descent, causing the motor to stop. The first is when the tension in the lift cord  120 ′ is relaxed. This happens, for example, when the bottom rail  104  meets with an obstruction, such a person&#39;s hand or an object on a window sill. In this first situation, the function of the lift cord detector  146  is to monitor the tension in the cord  120 ′. 
     The second situation is when the descending shade fully unwinds the lift cord  120 ′. In this latter case, as the reel shaft  124  makes its final rotation, it comes to a stop after bringing the end  142  of the lift cord  120 ′ past the reed  148  and thus, no longer in abutment therewith. In such case, the lift cord  120 ′ hangs from the reel shaft  124  in a position that is laterally displaced from the position it occupied when it was wrapped around the reel shaft  124 . In this second situation, the function of the cord detector  146  is to gauge the lateral position of the lift cord  120 ′ as it hangs from the reel  124 . 
     It should be noted that the function of gauging the lateral position of the lift cord may be performed a number of equivalent means. For instance, if the lift cord is thick enough, an optical sensor comprising an LED and a photodetector may suffice. The lift cord  120 ′ would then obstruct the light path in a first lateral position, and would not obstruct the light path in a second lateral position. And if the lift cord  120 ′ is formed from a metallic material, it may also be possible to arrange a magnetic sensor to detect a lateral movement of the lift cord  120 ′. Such sensors, however, would require power to operate, and would not be able to simultaneously detect tension; therefore, they are not preferred. 
     As shown in FIG. 8, the power supply for the assembly of the present invention is a battery pack  150  comprising eight 1.5V AA batteries  152 . The batteries, which preferably are non-rechargeable, are laid end-to-end, in electrical series with one another, thus providing 12 volts. The batteries are housed in a single elongated tube  150  which is mounted via brackets  154  fixed to the back side  156  of the head rail&#39;s front panel  114 . With the batteries  152  laid end-to-end and substantially parallel to the reel shaft  124 , substantially space savings is realized. This allows the motor, rotatable reel shaft, battery-based power supply, and electronics to be held within a housing having a cross-section less than 1¾″ by 1¾″. 
     A coil spring  158  mounted on the back side  156  biases a first end of the elongated tube  150 , forcing a positive battery terminal against a positive electrical contact positioned at the opposite, second end. A conductor strip  160  formed on an outer surface of the tube  150  connects the negative terminal of the battery pack  150  to a ring-shaped negative electrical contact  162 . Leads from each contact ultimately provide an electrical connection from the battery pack  150  to the PC board  126 , motor  122  and module  128 . 
     As depicted in FIG. 9, the motor  122  and its associated transmission  134  are assembled as a drive unit  164 , along with a protective drive plate  166 . The drive plate  166  is formed with an annular boss  168  through which the drive coupling  170  protrudes. A pair of diametrically opposed pins  172  secure the drive plate  166 , transmission  134  and motor  122  to each other. This facilitates assembly of the hardware within the head rail. 
     The drive unit  164  is mounted in an elongated aperture  174  formed in a bulkhead  176 . The bulkhead itself is rigidly fixed to the floor of head rail, on the inside surface of the latter&#39;s bottom panel  108 . Clips  178  formed on a bulkhead top panel  180  help retain the drive unit  164 . 
     As the bulkhead  176  is rigidly fixed to the head rail, any eccentricity in the motor  122  and drive unit  164  is transferred, in the form of vibrations, to the entire head rail  102 . This vibration is amplified by the head rail, causing the latter to emit annoying noises. To reduce vibrations imparted to the bulkhead  176  by the drive unit  164 , a resilient vibration dampening bushing  182  is used to mate the drive unit to the bulkhead. The bushing  182 , which preferably is formed from neoprene rubber having a Shore A hardness of between 60-70, has a substantially cylindrical base member  184 . The base member  184  is provided with a central aperture  186  shaped and sized to receive the annular boss  168  formed on the drive plate  166 , and is further provided with a pair of apertures  188  adapted and positioned to receive the pins  172 . On one side of its cylindrical base  184 , the bushing  178  is provided with an elongated boss  190  integrally formed therewith. The elongated boss is shaped and sized to be received by the elongated aperture  174  in the bulkhead. In this manner, the bushing  182  both supports the drive unit  164  within the head rail, and also provides vibration dampening to reduce motor noise during operation of the window covering  30 . 
     As shown in FIG. 12, one end of the drive rod  136  is integrally formed with a flange  192 . Preferably they are formed from a hard plastic, or the like. The flange  192  is rotatably mounted between a pair of upstanding ribs  194  supported on the inside surface of the head rail&#39;s bottom panel. The ribs prevent the drive rod  136  from moving in an axial direction as it is turned. One end of drive shaft  196  is connected to the drive rod  136  at the flange  192 . The opposite end of the drive shaft  196  is adapted to engage the transmission coupling  170  at a point between the bulkhead  176  and the flange  192 . Thus, coupling  170 , drive shaft  196 , flange  192  and drive rod  136  all turn together when the motor is operated. 
     Mounted on the drive shaft  196  is a star wheel  198 , which has four equidistantly spaced, radial spokes  200 . The star wheel  198  turns with the drive shaft  196  and the spokes interrupt a path between two objects, represented by  206   a ,  206   b . As the star wheel turns, the number of such interruptions is counted by a rotation counter. This number can then be translated into the number of revolutions of the reel shaft  124  relative to some starting point. The value in the rotation counter may then be used to compare with an upper or a lower limit count value saved in a memory register. 
     Either magnetic or optical sensing may be used in conjunction with the spokes  200 . For magnetic sensing, a permanent magnet  202  is attached, by adhesive or equivalent means, to the radially outward end of each spoke  200 . A magnetic sensor  204  comprising a pair of spaced apart sensor bars  206   a ,  206   b  is mounted on the underside of the PC-board  126 . As the star wheel  198  turns with the drive shaft, its magnet-tipped spokes  200  pass between the sensor bars. The number of resulting magnetic disturbances is then counted, and this number is used in the position determination. 
     Alternatively, instead of a magnetic sensor, an optical sensor may be used. In such case, a light emitting diode (LED)  206   a , arranged to emit light having a narrow wavelength, is positioned on one side of the star wheel  198 . A phototransistor  206   b  responsive to that wavelength is positioned on the other. The LED and phototransistor are used to count interruptions by the spokes, as disclosed in U.S. Pat. No. 4,856,574 to Minami, whose contents are incorporated by reference in their entirety. 
     In the present invention, to extend battery life, the magnetic sensor, or, alternatively, the LED and phototransistor, are powered and monitored only when the motor is running. More specifically, they are powered just an instant before the motor is activated, and they are turned off just after the motor stops running. 
     FIG. 13 presents a block diagram of the circuit  210  used to control the shade  106 . The battery pack  150  supplies all power to the circuit  210  via a power supply  212 . Power supply  212  provides battery protection, noise filtering and voltage regulation. It also outputs a 12 volt supply to power the motor, and a 5 volt supply to power the rest of the circuit. 
     The heart of the circuit is a microprocessor  214 , part no. 16C54. This processor is advantageous in that any port pin can be used for input or output. Also, an output port can put out a 5 volt signal capable of driving 25 mA of current. Thus, the processor itself acts as a low-current power supply of sorts. The processor is provided with a central processing unit, a non-volatile read-only memory (ROM), and a random access read-write memory (RAM). The ROM stores executable program code which is automatically entered upon booting the circuit by connecting the batteries. Alternatively, if a POWER ON switch is provided, this code is entered when such a switch is activated. The RAM includes a number of memory locations used for maintaining position data, status data, signal flags and the like. To extend battery life when there is no activity, the processor is cycled between a quiescent state and a sleep state. A built-in watchdog timer wakes up the processor from the sleep state. In the quiescent state, the processor  214  check a manual switch  130  and an IR receiver  216  to see if there are any inputs to which it should respond. If there are, the processor then enters an active state to process the input and take any other necessary action in response thereto. Upon conclusion of the active state, the processor is returned to the sleep state, after which the quiescent/sleep cycle is resumed. 
     The processor  214  is connected to the interface module  128 . A 5 volt power line, IRSIG, and a ground connection are supplied by the processor to the interface module  128 . Two signal lines, one from the manual switch  130 , MAN, and another from the IR receiver  216 , IRSIG, are returned to the processor. 
     The manual switch  130  can be either a contact switch, which activates a motor only when it is being depressed. Alternatively, switch  130  can be a single throw switch, which is activated once to start the motor, and activated a second time to stop the motor, unless, the motor stops by itself for some other reason. Either type of switch can be used, so long as the microprocessor  214  is appropriately programmed. Regardless of which type of switch is used, the switch output is presented on line MAN and this is read by the processor  214 . 
     In the preferred embodiment, an IR transmitter  218  having separate UP  220   a  and DOWN  220   b  buttons is used to remotely activate the shade. The IR transmitter is also provided with a two-position channel selection switch  222 , which allows a user to choose between two channels, A and B. The channel selection feature is especially advantageous in rooms where more than one window covering assembly is to be installed. 
     When either the UP or the DOWN button is pushed, a coded sequence of pulses corresponding to the button pushed and the channel selected, is generated. This sequence comprises a command signal. Each sequence has an identical number of pulses, and the sequence is repeated as long as the button is depressed. Each pulse in a sequence has a predetermined width of between 0.8 and 2.8 msec and is modulated with a 38 kHz carrier before being transmitted. 
     In the preferred embodiment, the IR receiver is a TFMS 5 . . . 0, available from TEMIC Telefunken. It filters and demodulates the sensed command signal and outputs a sequence of pulses corresponding to that generated within the transmitter  218  before being modulated. These pulses are output on line IRSIG and are read by the processor  214  by sampling to determine the length of each pulse. After reading the incoming sequence, the processor  214  matches it against a reference sequence stored in ROM. If a match occurs, the processor then sends out the appropriate signals to energize the motor, if other conditions are met. 
     To extend the life of the battery, the IR receiver  216  is cycled on and off by the processor  214  in one of two power cycle modes, a first, “look” mode, and a second, “active” mode. With no sensor activity and the motor off, the receiver  216  is normally in the look mode. In the look mode, power to the receiver  216  is alternatingly turned off for about 300 msecs, and then turned back on for about 7.1 msec. This means that, on average, a user must depress a transmitter button for about ⅓ second before any response can be expected. During the 7.1 msecs in which the receiver is powered, the processor checks the receiver output every 33 μsecs to see if a valid pulse, i.e., one between 0.8 and 2.8 msecs, has been received. Whether or not one has been received, the receiver  216  is turned off. 
     If no valid pulse has been received, the receiver is allowed to remain in the look mode. If, however, the microprocessor determines that a valid pulse was received, it then shifts the receiver into the active mode. In this mode, the receiver remains off for 9.5 msecs, and then is turned on for about 46 msecs, and a new alternating cycle of 9.5 msecs off and 46 msecs on, is established. When it is in the active mode, the receiver&#39;s output is checked by the processor every 160 μsecs. In the active mode, valid pulses, and even valid sequences of pulses (i.e., those sequences capable of activating the motor), may be received and interpreted by the processor  214 . 
     If neither a valid pulse, nor a valid sequence is received in that first 46 msec period of the active mode, the processor shifts the receiver back to the look mode beginning with the next off cycle. If, instead, a valid sequence is received, the processor  214  and associated circuitry turn on the motor  122 , and the receiver is allowed to remain in the active mode as long as the motor is running. Thus, with the motor running, the receiver is cycled off for 9.5 msecs and on for 46 msecs. Once the motor stops, whether due to a transmitted signal, or due the shade  106  reaching either an upper or a lower travel limit, or an obstruction, the receiver is shifted back into the look mode. 
     It should be noted that the above times are nominal values; actual times may vary by as much as 25%, depending on what other inputs the processor receives. It should also be noted that if the receiver output is continuously low for a predetermined number of cycles, e.g., 10 cycles, the receiver is considered to be in saturation. In such case, the processor shifts the receiver to the active mode to clear this situation. 
     In summary, then, the receiver  216  is switched between one of two power cycle modes. Both transmitted signals and motor status determine when the receiver is switched between the two modes. In a given mode, the length of time for which the receiver is turned on in each power-on, power-off cycle, is substantially the same. Also, the length of time for which power is continuously connected to the RR receiver  216  is independent of the content of the data received during that connection period. Thus, even if a valid pulse is received during a power-on period, power to receiver will be disconnected at the end of that period. This differs from the aforementioned U.S. Pat. No. 5,134,347 to Koleda, whose contents are incorporated by reference in their entirety, wherein power to the receiver is continued if a valid signal is received in the look mode. 
     To activate the motor  122 , four control lines  224  are connected between the processor  214  and a bridge circuit  226 . Two of the four control lines are connected to base terminals of a pair of NPN bipolar junction transistors (BJTs), each of which serves as a switch to control one half of the bridge circuit  226 . The remaining two control lines are connected to the gate terminals of a pair of low power field effect transistors (MOSFETs). Each of the MOSFETs forms the lower portion of one half of the bridge circuit  226 , allowing current to flow through its corresponding half when that FET&#39;s gate is activated by the processor  214 . 
     The circuit  210  includes a sensor subcircuit  228  which gathers status information from one of three different sensors. The microprocessor powers the sensor subcircuit  228  at predetermined times through line IPWR, which is connected to resistor R 3 , and reads the sensor output through line INP. To read a particular sensor, it must first be enabled through a dedicated line DRV_CS, DRV_LL and OPT_LED from the processor  214 . 
     One of the three sensors is a channel select strap  230 . The channel select strap  230  allows a user to enable the processor  214  to match a received command signal only with stored sequences corresponding to the selected channel. Preferably, the channel select strap  230  can be accessed either from outside the head rail or by simply opening its hinged front panel  114 . The channel select strap can be formed as a simple wire or a jumper connector connecting two pins or leads. Alternatively, it can be formed as a two-position switch, much like the channel selector  222  on the transmitter  218 . When the wire or jumper connector is intact, the processor  214  will try to match received command signals with stored sequences corresponding to channel A. And when the wire or jumper connector is not in place, e.g, when the wire is cut or the jumper connector is removed, the processor tries to match received command signals with stored sequences corresponding to channel B. 
     To determine which channel has been selected, the processor  214  powers the sensor subcircuit  228  using line IPWR, enables the channel select strap using line DRV_CS, and reads the input on line INP. In normal use, the channel selector strap  230  is only examined (i.e., IPWR and DRV_CS are both activated and INP is monitored) upon power start-up. As stated above, power start-up takes place when the batteries are first connected or when the power switch is activated, if a power switch is provided. Thereafter, if the channel select strap  230  is altered to designate a different channel, the processor  214  will continue to match received sequences only against stored sequences corresponding to the previous channel. Thus, after changing the channel select strap, the power must first be turned off before the processor  214  will recognize sequences corresponding to the newly directed channel. 
     One skilled in the art will recognize that the channel select strap  230  may be configured to allow one to select from among more than two channels. This can be done, for instance, by using a plurality of jumper connectors or a dip switch, or other device, which allows only one channel to be designated at a time. In such case, the processor  214  must connect an enable line, similar to DRV_CS, to each of these channel selection connectors and selectively activate them upon start-up. Alternatively, the processor  214  may output a set of coded enable lines which are then connected to a multiplexer, and from there to each of the channel selection connectors. If a plurality of channels are provided, the processor  214  must also store UP and DOWN sequences for each of these channels, and these sequences must include enough pulses to uniquely code for the chosen number of channels. Finally, the transmitter  218  should be provided with a multi-position switch or dial, allowing it to select from among the various channels and output corresponding UP and DOWN sequences. Such a configuration can allow a single transmitter to selectively control a plurality of shades. 
     The second sensor monitored by the processor  214  is the lift cord detector  146 , discussed above. To determine whether the lift cord  120 ′ is abutting the lift cord detector  146 , the processor  214  powers the sensor subcircuit  228  using line IPWR, enables the lift cord detector  146  using line DRV_LL, and reads the input on line INP. It should be noted that current to the motor does not flow through the lift cord detector  146 ; only a current and voltage sufficient to be detected by the processor  214  is necessary. 
     The third sensor monitored by the processor  214  is used to count the number of interruptions made by the star wheel  198 , and thus indirectly count the number of revolutions that the drive shaft  196  turns. As represented by the dashed line  234  from the motor  122  to the sensor  232 , motor rotation is indirectly coupled to the sensor  232  in this manner. In the preferred embodiment, the third sensor  232  is an electro-optic sensor  232 , although a magnetic sensor may also be used, as explained above. The electro-optic sensor creates a light path which is interrupted by the star wheel  198 . The sensor  232  comprises a light emitting diode LED 1  and a phototransistor PT 1 . As the motor  122  turns, so does the star wheel  198 , and the interruptions of the star wheel affect the output of the phototransistor PT 1 . 
     As explained above, the electro-optic sensor  232  operates only when the motor is just about to run and continues to operate so long as the motor is running. Thus, to activate the electro-optic sensor  232 , the processor powers the sensor subcircuit using line IPWR, enables the light emitting diode LED 1  using line OPT_LED and reads the input on line INP. Each time the star wheel  198  interrupts the path between LED 1  and PT 1 , this interruption is sensed by the processor on line INP. 
     Thus, when the motor is just about to run, and also while the motor is running, the processor  214  powers the sensor subcircuit  228 . It then periodically enables the cord detector  146  with line DRV_LL and reads the input on line INP, and also periodically enables LED 1  and reads the input on INP. 
     In this manner, the microprocessor monitors these sensors with a single sensor input line. After power startup, only the lift cord detector  146  and the optical sensor  232  are monitored. And even these two are monitored only if the processor has been directed to turn on the motor  122  asked to turn on by either the transmitter  218  or by the manual switch  130 . 
     FIG. 14 presents a circuit diagram of the power supply. Power is supplied by the battery pack  150 . Diode D 3  provides battery reversal protection. The power supply provides a 12 volt source to drive the motor and a 5 volt source to drive the remainder of the circuit. A voltage regulator U 2 , which has a quiescent current of about 1 μA, is always on, providing a 5 volt source. Capacitors C 1  and C 2  and resistor R 1  filter motor noise connected to the 12 volt supply. This prevents the motor noise from affecting the voltage regulator U 2 . Capacitor C 3  provides added power filtering. The values of the resistors and capacitors for the entire circuit are presented in Table 1. 
     FIG. 15 shows input and output lines connected to the processor  214 . Resistor R 2  and capacitor C 5  from an oscillator at nominally 2.05 MHz (plus or minus 25%). This provides an internal timing clock for the processor. 
     FIG. 16 presents the circuitry of the interface module  128 . A 4-pin connector J 3  on the interface module  128  communicates with a 4-pin connector J 3  on the PC-board. As explained above, the four lines include an IR receiver power line IRPWR, an IR receiver signal line IRSIG, which is active low, a ground connection shared by both the manual switch  130  and the IR receiver  216  IRSIG, and the manual switch output line MAN which is pulled high by pull-up resistor R 5 , and is also active low. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
               
               
                 COMPONENT 
                 VALUE 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 C1 
                 10 
                 mF 
               
               
                 C2 
                 10 
                 mF 
               
               
                 C3 
                 10 
                 mF 
               
               
                 C5 
                 22 
                 pF 
               
               
                 C6 
                 0.1 
                 μF 
               
               
                 R1 
                 51 
                 kΩ 
               
               
                 R2 
                 10 
                 kΩ 
               
               
                 R3 
                 100 
                 kΩ 
               
               
                 R4 
                 300 
                 kΩ 
               
               
                 R5 
                 100 
                 kΩ 
               
               
                 R6 
                 1 
                 kΩ 
               
               
                 R7 
                 1 
                 kΩ 
               
               
                 R8 
                 1 
                 kΩ 
               
               
                 R9 
                 620 
                 Ω 
               
               
                   
               
             
          
         
       
     
     Table 1—Component Values 
     FIG. 17 shows a circuit diagram of the sensor subcircuit  228 . To enable any of the sensors, the processor  214  must apply power to the circuit by driving IPWR high (i.e., 5 volts) and monitor line INP. The processor must also enable the sensor it wishes to monitor by driving one of normally high OPT-LED, DRV_LL and DRV_CS lines low (i.e., setting it to 0 volts). 
     To determine the state of the channel selector strap  230  upon power startup, the processor  214  drives IPWR high, drives DRV_CS low (i.e., sets it to 0 volts) and monitors INP. If INP is low, the channel selector switch is deemed to be intact, and so the processor is informed that it should match incoming signals against reference sequences for channel A. If, on the other hand, INP is high, there is no continuity across the channel select strap  230 , and the processor knows to match for channel B. 
     To determine the state of the lift cord detector  146 , the processor again drives IPWR high, drives DRV_LL low, and monitors INP. If INP is low, this indicates that the detector&#39;s reed  148  is closed and so the lift cord  120 ′ must be abutting the reed  148 . This will inform the processor that there is tension in the lift cord  120 ′ and that the shade is not at the bottom. 
     Finally, to activate the optical sensor  232 , the processor  214  drives IPWR high, OPT-LED low, and monitors INP. This allows current to flow through LED 1 , causing it to emit light. This light is sensed by the phototransistor PT 1 , causing it to conduct and voltage to drop across resistor R 3 . Thus, when PT 1  conducts, line INP is low. Each time the star wheel  198  interrupts the path between LED 1  and PT 1 , line INP temporarily goes high. The number of times this line transitions from low to high and back to low is counted by the processor  214 , and this number is translated into the number of rotations of the reel shaft  124  relative to some starting point. 
     When the motor is energized, the optical sensor  232  and star wheel  198  serve a second purpose. Each time the motor  122  is activated, the processor  214  starts an internal stall timer, which is formed as a register in memory. The stall timer times the interruptions of the magnetic or optical path, as caused by the spokes  200  of the star wheel  198 . Each time an interruption occurs, the stall timer is reset. If the stall timer times out, it means that successive interruptions did not take place as quickly as they should have, and so the drive shaft  196  (and hence, the motor  122 ) did not turn as they should. This indicates a motor stall condition, such as when the shade is fully closed and can go no higher. Thus, whenever the motor  122  is running, the processor  214  checks for motor stall. If a stall is detected by the processor  214 , it then no longer activates the motor  122 , thus preventing damage to electrical and mechanical components of the assembly  100 . 
     FIG. 18 presents the circuit diagram of the H-bridge circuit  226 . Four lines from the processor control the bridge. Lines HLP and HRP control the H-bridge&#39;s left and right P-circuit, respectively, and lines HLN and HRN control the H-bridge&#39;s left and right N-circuit, respectively. As shown in FIG. 17, the P-circuit controls the upper half of the H-bridge, and the N-circuit controls the lower half of the H-bridge. 
     As shown in FIG. 18, lines HLP and HRP are connected to the base leads of left and right NPN switching transistors Q 1  and Q 3 , through an associated current limiting resistor R 6  or R 8 . When either line HLP or line HRP is driven high by the processor  214 , the corresponding base-emitter junction on Q 1  or Q 3  is forward biased, allowing current to flow through that transistor, assuming other conditions are met. The collectors of Q 1  and Q 3  are connected via resistors R 7  and R 9  to the base leads of associated respective left Q 2  and right Q 4  PNP power transistors. The emitters of these two power transistors, Q 2  and Q 4 , are connected to the 12 volt power supply, while their collectors are connected to separate leads of a connector J 5 . Connector J 5 , in turn, is connected to corresponding leads of the motor  122 , allowing the latter to be energized in either direction. 
     Lines HLN and HRN are connected to the gates of N-channel MOSFETs Q 5  and Q 6 , respectively. These lines are normally high when the motor  122  is not activated, thus turning on the Q 5 , Q 6 . This is the brake condition, which blocks current from passing from the collectors of Q 3  and Q 4 , through the MOSFETs and on to ground. 
     When the motor  122  is to be activated in a first direction, HLP is driven high and HLN is driven low simultaneously. And, when the motor is to be activated in a second direction, HRP is driven high and HRN is driven low. In this manner, the bridge circuitry is configured to activate the motor in either direction. While the motor  122  is running, diodes D 2  and D 3  provide protection from back electromotive force (EMF) from the motor  122  and capacitor C 6  filters some of the high frequency noise from the motor  122 . 
     The operation of the window covering assembly  100  is described next. As discussed above, the processor&#39;s RAM comprises a number of storage locations which keep track of sensor and status data. Among these storage locations are: a) a rotation counter, b) an upper limit register, which keeps track of the upper limit to which the shade may rise, c) a looking-for-upper-limit flag, which keeps track of whether or not the processor should look for an upper limit, d) a channel register, which keeps track of which channel&#39;s reference sequences should be used for matching with the received sequences, and e) a direction register, which keeps track of the last direction of shade travel. 
     On power startup, the rotation counter and upper limit counter are both set to a large, predetermined value, indicating that there is no upper limit, and the looking-for-upper-limit flag is set to not look for an upper limit. Also, the last direction counter is set to up (so that if the manual switch  130  is pushed, the shade will go down), and the channel register is set to A or B, depending on the channel strap. 
     After these registers are initialized, the processor enters a quiescent state in which the processor  214  first checks whether the manual switch  130  has been pushed. If the manual switch  130  has not been pushed, the processor next turns on the IR receiver  216  for 7.1 msec and then turns it off. If no valid pulse was received within that period, the processor enters a sleep state for a predetermined period of time, about 300 msecs. As it enters the sleep state, the processor  214  makes sure that the transistors Q 2  and Q 4  are off, MOSFETs Q 5  and Q 6  are on (brake) and that all other outputs and sensors are off. After waking up, the processor  214  loops through the quiescent state once again. If, during the quiescent state, either the manual switch  130  is pushed or a valid pulse is received, the processor  214  enters the active state. 
     In the active state, the processor  216  processes the input, and takes any necessary action in response, such as activating the motor  122 . When the motor is running, the IR receiver is  216  is placed in the active mode and the processor  216  checks IRSIG, checks the lift cord detector  146 , updates the rotation counter with each interruption, and checks the stall timer, and the manual switch  130 . 
     At any given time, the shade  106  can be in one of three positions: 1) shade fully up (open), 2) shade fully down (closed), and 3) the shade partially down. Also, as stated above, the shade can be activated by either a) the manual switch  130 , or b) either button  220   a ,  220   b  on the transmitter  218 . This gives a total of six combinations, or examples, to illustrate processor behavior, when in the active state. 
     EXAMPLE 1 
     Shade  106  fully up (open) and the manual switch  130  pushed. In this case, the lift cord detector  146  is abutted by the cord  120 ′, and so is closed. The processor  214  first checks the direction register and determines in which direction the shade  106  last travelled. 
     Case l a . Last direction of travel was “up”. The appropriate half of the bridge circuit is turned on, and, after an appropriate delay to avoid a short circuit, the other half of the bridge circuit is turned off. The motor is turned on and the shade goes down. The shade will continue to travel downward until a) the lift cord detector  146  is opened by rotating the cord  120 ′ off the reed  148  when the shade reaches the bottom of its travel, b) the shade encounters an obstacle, relieving tension in the cord  120 ′ and causing it to no longer abut the reed  148 , c) the manual switch  120  is pushed a second time, or d) either transmitter button  220   a ,  220   b  is pushed. Regardless of which of these events take place, the direction register is toggled to indicate that the last direction was “down”, and motor and shade are stopped, after which the processor enters the sleep state. 
     Case  1   b . Last direction of travel was “down”. The processor will first check to see whether the shade is at the upper limit (i.e., the value in the rotation counter matches that in the upper limit register). If this is the case, the processor will ignore the manual switch and enter the sleep state. If, for whatever reason, the rotation counter indicates that upper limit has not been reached, the processor  214  will activate the motor  122  to try to force the shade up. As the shade will not go up, the stall timer will immediately time out, causing the processor to deactivate the motor. Following this, the direction register is toggled to indicate that the last direction was “up”, and the processor enters the sleep state. 
     EXAMPLE 2 
     Shade  106  fully up (closed) and a transmitter  218  button is pushed. Again, the lift cord detector  146  will be closed. The processor  214  ignores the direction register and determines which button was pushed. 
     Case  2   a . Down button  220   b  is pushed. The shade will go down. The processor and shade will behave in the same way as in Case  1   a , except that the shade will stop if either transmitter button  220   a ,  220   b  is pushed a second time. 
     Case  2   b . Up button  220   a  is pushed. The processor and shade will behave in the same way as in Case  1   b . Again, the stall timer will time out, causing the motor to stop, after which the processor will toggle the direction register, and then enter the sleep state. 
     EXAMPLE 3 
     Shade  106  fully down (closed) and the manual switch  130  pushed. In this case, the lift cord detector  146  will be open, indicating that either the shade is fully lowered, or that the shade is resting on an object. The processor  214  first checks the direction register and determines in which direction the shade  106  last travelled. 
     Case  3   a . Last direction of travel was “up”. The processor  214  will determine that the lift cord detector is open. Because it is open, the processor will not allow the shade to be lowered, and so will enter the sleep state. 
     Case  3   b . Last direction of travel was “down”. The processor will determine that the lift cord detector is open. This will cause it to reset the rotation counter to zero, and enable the looking-for-upper-limit flag so that, upon ascent, the processor will compare the value in the rotation counter to the value in the upper limit register. The processor will then activate the motor to raise the shade. The shade will continue to travel upward until a) the stall timer times out, indicating that the motor has stalled (e.g., the shade is fully raised), b) the rotation counter reaches the value in the upper limit register, c) the manual button is pushed a second time, or d) either transmitter button  220   a ,  220   b  is pushed. Regardless of which of these events take place, the direction register is toggled to indicate that the last direction was “up”, and motor and shade are stopped, after which the processor enters the sleep state. 
     EXAMPLE 4 
     Shade  106  fully down (closed) and a transmitter  218  button is pushed. Again, the lift cord detector  146  will be open, indicating that either the shade is fully lowered, or that the shade is resting on an object. The processor  214  ignores the direction register and determines which button was pushed. 
     Case  4   a . Down button  220   b  is pushed. The processor  214  will determine that the lift cord detector is open and so it will not activate the motor to lower the shade. If the button  220   b  is pushed for less than 3 seconds, nothing else happens and the processor enters the sleep state. If, however, the button  220   b  is pushed for 3 seconds or longer, the upper limit counter is set to a large, predetermined value, indicating that there is no upper limit. After this, the processor enters the sleep state. 
     Case  4   b . Up button  220   a  is pushed. The processor and shade will behave in substantially the same way as in Case  3   b , except that the shade will stop if either transmitter button  220   a ,  220   b  is pushed a second time. Additionally, however, if a stall is detected when the shade is being raised from the lower limit, a new upper limit will be set. For this, the upper limit register will be set to 5 pulses less than the rotation counter, which has been reset to zero just before the shade began to rise. The new upper limit value will help ensure that the next time the shade is raised, (after first having been lowered), the shade will stop at the new upper limit, instead of continuing on and encountering a stall condition. 
     EXAMPLE 5 
     Shade  106  partially open and the manual switch  130  pushed. In this case, the lift cord detector  146  is abutted by the cord  120 ′, and so is closed. The processor  214  first checks the direction register and determines in which direction the shade  106  last travelled. 
     Case  5   a . Last direction of travel was “up”. The shade will go down until a) the lift cord detector  146  is opened by rotating the cord  120 ′ off the reed  148  when the shade reaches the bottom of its travel, b) the shade encounters an obstacle, relieving tension in the cord  120 ′ and causing it to no longer abut the reed  148 , c) the manual switch  120  is pushed a second time, or d) either transmitter button  220   a ,  220   b  is pushed. Regardless of which of these events take place, the direction register is toggled to indicate that the last direction was “down”, and motor and shade are stopped, after which the processor enters the sleep state. This is similar to Case  1   a.    
     Case  5   b . Last direction of travel was “down”. The processor will first check to see whether the shade is at the upper limit (i.e., the value in the rotation counter matches that in the upper limit register). If this is the case, the processor will ignore the manual switch and enter the sleep state. If the upper limit has not been reached, the shade will go up until a) the stall timer times out, indicating that the motor has stalled (e.g., the shade is fully raised), b) the rotation counter reaches the value in the upper limit register, c) the manual button is pushed a second time, or d) either transmitter button  220   a ,  220   b  is pushed. Regardless of which of these events take place, the direction register is toggled to indicate that the last direction was “up”, and motor and shade are stopped, after which the processor enters the sleep state. 
     EXAMPLE 6 
     Shade  106  partially open and a transmitter  218  button is pushed. Again, the lift cord detector  146  is abutted by the cord  120 ′, and so is closed. The processor ignores the direction register and determines which button was pushed. 
     Case  6   a . Down button  220   b  is pushed. The processor and shade will behave in the same way as in Case  5   a , except that the shade will stop if either transmitter button  220   a ,  220   b  is pushed a second time. 
     Case  6   b . Up button  220   a  is pushed. The processor and shade will behave in the same way as in Case  5   b , except that the shade will stop if either transmitter button  220   a ,  220   b  is pushed a second time. 
     The processor  214  executes a series of software instructions to control the window covering assembly. FIGS.  19  and  19 -A to  19 -J present a flowchart which illustrates this software control. Processor operation begins with powering up the system in step  300 . This is followed by step  302  in which various registers, counters and flags are initialized, and the channel strap is read. Once this initialization is finished, the processor enters the quiescent state in which the processor looks for activity from either the manual switch  130  or the IR receiver  216 . 
     In step  304 , the processor checks line MAN to see if the manual switch has been pushed. If so, control flows to step  314  in FIG. 19-A. If, however, the manual switch  130  has not been pushed, the IR receiver is turned on for 7.1 msecs and then turned off in the look mode (step  306 ). The processor then samples IRSIG to see whether a valid pulse was received (step  308 ). If so, control flows to step  316  in FIG. 19-B, If, however, no valid pulse was received, the processor enters a sleep mode (step  308 ) in which it remains, nominally, for 300 msecs before waking up (step  312 ). The processor then continues in the quiescent state with control looping back to step  304  to see if the manual switch  130  was pushed. 
     FIG. 19-A illustrates the control sequence when the manual switch was pushed when the processor was in the quiescent state. In step  314 , the processor checks the direction register to see in which direction the shade last was asked to move. If the last direction was UP, it means that the shade should go down, and so control flows to step  332  in FIG. 19-D. If, on the other hand, the last direction was DOWN, the shade should now go up, and so control flows to step  324  in FIG. 19-C. 
     FIG. 19-B illustrates the control sequence when a valid pulse was received when the processor was in the quiescent state. First, in step  316 , the processor places the IR receiver  216  in the active mode, discussed above. Next, in step  318 , the processor attempts to match the received sequence of pulses with the reference sequences for the selected channel. If there is no match, the processor enters the sleep state (step  310 ). If there is a match, the processor determines which button on the transmitter, UP or DOWN, was pushed (step  320 ). If the UP button was pushed, control goes to step  324  in FIG. 19-C. If the DOWN button was pushed, the processor checks to see whether the lift cord detector reed is open (step  322 ). If the detector is not open, control goes to step  322  in FIG. 19-D; if it is open (indicating that the shade is either fully lowered or resting on an object), control goes to step  334  in FIG. 19-E. 
     FIG. 19-C illustrates the control sequence when the processor has been instructed by either the manual switch or the transmitter to raise the shade. The processor first determines whether the lift cord detector reed is open (i.e., whether the shade is fully lowered or is resting on an object) (step  324 ). If the detector is open, then the shade resets the rotation counter and sets the looking-for-upper-limit flag (step  326 ), and then turns on the motor to raise the shade (step  330 ). If the detector is closed, the processor first checks whether the shade is at the upper limit (step  328 ). If the shade is already at its upper limit, the shade need not be raised, and so the processor goes to sleep (step  310 ). On the other hand, if the shade is not already at its upper limit, it can rise some more, and so the processor turns on the motor to raise the shade (step  330 ). Whether or not the lift reed was open, control goes to step  344  in FIG. 19-F, after the motor starts. 
     FIG. 19-D illustrates the control sequence when the processor has been instructed by either the manual switch or the transmitter to lower the shade. The motor is simply turned on to lower the shade (step  332 ), after which control passes to step  344  in FIG. 19-F. 
     FIG. 19-E illustrates the control sequence when the lift cord detector reed is open and the down button on the transmitter has been pushed. The processor first starts a 3-second timer (step  334 ), which is used to determine whether the down button is pressed for the full three seconds. The IR receiver is maintained in the active mode (step  336 ) and the processor checks the IRSIG line to see whether the DOWN button is still being pressed (step  338 ). If the DOWN button stops being pressed at any time within those three seconds, the processor enters the sleep state (step  310 ), as the shade cannot be lowered (since the lift cord detector reed is open). The processor stays keeps checking the IRSIG line until either the DOWN button is released or until the 3 seconds are over (step  340 ), whichever occurs first. If the 3-second timer times out, the upper limit counter is reset (step  342 ), and the processor enters the sleep state (step  310 ). 
     FIG. 19-F illustrates the control sequence when the motor is running, either up or down. With the motor running, the IR receiver is in the active mode, the IRSIG and MAN lines from the interface module  128  are monitored, the optical sensor  232 , and the lift detector reed  148  are polled, and the stall timer is operational (step  344 ). The processor then executes a loop to check on all of these. 
     When the IRSIG line is being monitored (step  346 ), control flows to step  358  in FIG. 19-G. When the processor polls the lift cord detector reed  148 , it determines whether the reed is open (step  348 ). If so, control goes to step  362  in FIG. 19-H. When the processor polls the optical sensor (i.e, the phototransistor) it determines whether the light path has been interrupted (step  350 ). If so, control goes to step  366  in FIG. 19-I. If the stall timer times out (step  352 ), control goes to step  372  in FIG. 19-J. And when the MAN line is being monitored (step  354 ), the processor is interested in knowing whether the manual switch  130  has been pushed anew since the motor started running. If the manual switch has not been pushed anew, the motor continues to run and the processor continues to check the various inputs. If, however, it has been pushed anew, the motor is stopped (step  356 ) and the processor eventually enters the sleep state (step  310 ). 
     FIG. 19-G illustrates the control sequence when the motor is running and the IR receiver is being monitored. The processor checks to see if line IRSIG is active and if it is, whether either transmitter button has been pushed anew since the motor started running (step  358 ). If neither button has been pushed anew, the motor continues to run and the processor continues to check the various inputs. If, however, either button has been pushed anew, the motor is stopped (step  360 ) and the processor eventually enters the sleep state (step  310 ). 
     FIG. 19-H illustrates the control sequence when the motor is running and the lift cord detector reed is opened. The processor first checks to see whether the shade was going down when this happened (step  362 ). If it was going down, the motor is stopped ( 364 ), because the cord has fully unwound or because the shade bumped into an obstacle on the way down. After the motor is stopped, the processor enters the sleep state (step  310 ). If, on the other hand, the shade was going up, the processor doesn&#39;t care, and the motor continues to run and raise the shade. 
     FIG. 19-I illustrates the control sequence when the motor is running and an interruption in the light path is detected. Whenever the light path is interrupted, it means star wheel  198 , and thus the reel  124  are turning, the shade is either being raised or lowered, and the motor is not stall condition. Thus, the processor resets the stall timer and increments the rotation counter (step  366 ). The processor then compares the rotation counter to the value in the upper limit register (step  368 ). If they do not match, it means that the upper limit for the shade has not been met, and the motor continues to run. If, on the other hand, they match, the upper limit has been reached. In such case, the motor is stopped (step  370 ), and the processor enters the sleep state (step  310 ). 
     FIG. 19-J illustrates the control sequence when the motor is running and the stall timer times out. When this happens, it means that the star wheel  198  and the reel  124  did not turn, even though the motor was on, thus indicating a motor stall condition. A motor stall can happen when the shade is all the way up and the rotation counter does not match the value in the upper limit register. It can also happen if the shade is held by an object which prevents the former from rising. Other situations may also cause the timer to time out. Regardless of what causes this, the motor is first stopped (step  372 ). The processor then checks whether the rotation counter was to stop when it reached the value in the upper limit register (step  374 ). If so, the upper limit register is set to a value slightly below the current rotation count (step  376 ). This will prevent stall due to a spurious upper limit register value, on a subsequent raising of the blind. After step  376  and also, in the event that the rotation counter was not to be matched against the upper limit register value, the processor enters the sleep state (step  310 ). 
     While the above invention has been described with reference to certain preferred embodiments, it should be kept in mind that the scope of the present invention is not limited to these. One skilled in the art may find variations of these preferred embodiments which, nevertheless, fall within the spirit of the present invention, whose scope is defined by the claims set forth below.