A movable barrier operator having improved safety and energy efficiency features automatically detects line voltage frequency and uses that information to set a worklight shut-off time. The operator automatically detects the type of door (single panel or segmented) and uses that information to set a maximum speed of door travel. The operator moves the door with a linearly variable speed from start of travel to stop for smooth and quiet performance. The operator provides for full door closure by driving the door into the floor when the DOWN limit is reached and no auto-reverse condition has been detected. The operator provides for user selection of a minimum stop speed for easy starting and stopping of sticky or binding doors.

BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to movable barrier operators for operating movable barriers or doors. More particularly, it relates to garage door operators having improved safety and energy efficiency features.  
           [0002]    Garage door operators have become more sophisticated over the years providing users with increased convenience and security. However, users continue to desire further improvements and new features such as increased energy efficiency, ease of installation, automatic configuration, and aesthetic features, such as quiet, smooth operation.  
           [0003]    In some markets energy costs are significant. Thus energy efficiency options such as lower horsepower motors and user control over the worklight functions are important to garage door operator owners. For example, most garage door operators have a worklight which turns on when the operator is commanded to move the door and shuts off a fixed period of time after the door stops. In the United States, an illumination period of 4½ minutes is considered adequate. In markets outside the United States, 4½ minutes is considered too long. Some garage door operators have special safety features, for example, which enable the worklight whenever the obstacle detection beam is broken by an intruder passing through an open garage door. Some users may wish to disable the worklight in this situation. There is a need for a garage door operator which can be automatically configured for predefined energy saving features, such as worklight shut-off time.  
           [0004]    Some movable barrier operators include a flasher module which causes a small light to flash or blink whenever the barrier is commanded to move. The flasher module provides some warning when the barrier is moving. There is a need for an improved flasher unit which provides even greater warning to the user when the barrier is commanded to move.  
           [0005]    Another feature desired in many markets is a smooth, quiet motor and transmission. Most garage door operators have AC motors because they are less expensive than DC motors. However, AC motors are generally noisier than DC motors.  
           [0006]    Most garage door operators employ only one or two speeds of travel. Single speed operation, i.e., the motor immediately ramps up to full operating speed, can create a jarring start to the door. Then during closing, when the door approaches the floor at full operating speed, whether a DC or AC motor is used, the door closes abruptly with a high amount of tension on it from the inertia of the system. This jarring is hard on the transmission and the door and is annoying to the user.  
           [0007]    If two operating speeds are used, the motor would be started at a slow speed, usually 20 percent of full operating speed, then after a fixed period of time, the motor speed would increase to full operating speed. Similarly, when the door reaches a fixed point above/below the close/open limit, the operator would decrease the motor speed to 20 percent of the maximum operating speed. While this two speed operation may eliminate some of the hard starts and stops, the speed changes can be noisy and do not occur smoothly, causing stress on the transmission. There is a need for a garage door operator which opens the door smoothly and quietly, with no aburptly apparent sign of speed change during operation.  
           [0008]    Garage doors come in many types and sizes and thus different travel speeds are required for them. For example, a one-piece door will be movable through a shorter total travel distance and need to travel slower for safety reasons than a segmented door with a longer total travel distance. To accommodate the two door types, many garage door operators include two sprockets for driving the transmission. At installation, the installer must determine what type of door is to be driven, then select the appropriate sprocket to attach to the transmission. This takes additional time and if the installer is the user, may require several attempts before matching the correct sprocket for the door. There is a need for a garage door operator which automatically configures travel speed depending on size and weight of the door.  
           [0009]    National safety standards dictate that a garage door operator perform a safety reversal (auto-reverse) when an object is detected only one inch above the DOWN limit or floor. To satisfy these safety requirements, most garage door operators include an obstacle detection system, located near the bottom of the door travel. This prevents the door from closing on objects or persons that may be in the door path. Such obstacle detection systems often include an infrared source and detector located on opposite sides of the door frame. The obstacle detector sends a signal when the infrared beam between the source and detector is broken, indicating an obstacle is detected. In response to the obstacle signal, the operator causes an automatic safety reversal. The door stops and begins traveling up, away from the obstacle.  
           [0010]    There are two different “forces” used in the operation of the garage door operator. The first “force” is usually preset or setable at two force levels: the UP force level setting used to determine the speed at which the door travels in the UP direction and the DOWN force level setting used to determine the speed at which the door travels in the DOWN direction. The second “force” is the force level determined by the decrease in motor speed due to an external force applied to the door, i.e., from an obstacle or the floor. This external force level is also preset or setable and is any set-point type force against which the feedback force signal is compared. When the system determines the set point force has been met, an auto-reverse or stop is commanded.  
           [0011]    To overcome differences in door installations, i.e. stickiness and resistance to movement and other varying frictional-type forces, some garage door operators permit the maximum force (the second force) used to drive the speed of travel to be varied manually. This, however, affects the system's auto-reverse operation based on force. The auto-reverse system based on force initiates an auto-reverse if the force on the door exceeds the maximum force setting (the second force) by some predetermined amount. If the user increases the force setting to drive the door through a “sticky” section of travel, the user may inadvertently affect the force to a much greater value than is safe for the unit to operate during normal use. For example, if the DOWN force setting is set so high that it is only a small incremental value less than the force setting which initiates an auto-reverse due to force, this causes the door to engage objects at a higher speed before reaching the auto-reverse force setting. While the obstacle detection system will cause the door to auto-reverse, the speed and force at which the door hits the obstacle may cause harm to the obstacle and/or the door.  
           [0012]    Barrier movement operators should perform a safety reversal off an obstruction which is only marginally higher than the floor, yet still close the door safely against the floor. In operator systems where the door moves at a high speed, the relatively large momentum of the moving parts, including the door, accomplishes complete closure. In systems with a soft closure, where the door speed decreases from full maximum to a small percentage of full maximum when closing, there may be insufficient momentum in the door or system to accomplish a full closure. For example, even if the door is positioned at the floor, there is sometimes sufficient play in the trolley of the operator to-allow the door to move if the user were to try to open it. In particular, in systems employing a DC motor, when the DC motor is shut off, it becomes a dynamic brake. If the door isn't quite at the floor when the DOWN travel limit is reached and the DC motor is shut off, the door and associated moving parts may not have sufficient momentum to overcome the braking force of the DC motor. There is a need for a garage door operator which closes the door completely, eliminating play in the door after closure.  
           [0013]    Many garage door operator installations are made to existing garage doors. The amount of force needed to drive the door varies depending on type of door and the quality of the door frame and installation. As a result, some doors are “stickier” than others, requiring greater force to move them through the entire length of travel. If the door is started and stopped using the full operating speed, stickiness is not usually a problem. However, if the garage door operator is capable of operation at two speeds, stickiness becomes a larger problem at the lower speed. In some installations, a force sufficient to run at 20 percent of normal speed is too small to start some doors moving. There is a need for a garage door operator which automatically controls force output and thus start and stop speeds.  
         SUMMARY OF THE INVENTION  
         [0014]    A movable barrier operator having an electric motor for driving a garage door, a gate or other barrier is operated from a source of AC current. The movable barrier operator includes circuitry for automatically detecting the incoming AC line voltage and frequency of the alternating current. By automatically detecting the incoming AC line voltage and determining the frequency, the operator can automatically configure itself to certain user preferences. This occurs without either the user or the installer having to adjust or program the operator. The movable barrier operator includes a worklight for illuminating its immediate surroundings such as the interior of a garage. The barrier operator senses the power line frequency (typically 50 Hz or 60 Hz) to automatically set an appropriate shut-off time for a worklight. Because the power line frequency in Europe is 50 Hz and in the U.S. is 60 Hz, sensing the power line frequency enables the operator to configure itself for either a European or a U.S. market with no user or installer modifications. For U.S. users, the worklight shut-off time is set to preferably 4½ minutes; for European users, the worklight shut-off time is set to preferably 2½ minutes. Thus, a single barrier movement operator can be sold in two different markets with automatic setup, saving installation time.  
           [0015]    The movable barrier operator of the present invention automatically detects if an optional flasher module is present. If the module is present, when the door is commanded to move, the operator causes the flasher module to operate. With the flasher module present, the operator also delays operation of the motor for a brief period, say one or two seconds. This delay period with the flasher module blinking before door movement provides an added safety feature to users which warns them of impending door travel (e.g. if activated by an unseen transmitter).  
           [0016]    The movable barrier operator of the present invention drives the barrier, which may be a door or a gate, at a variable speed. After motor start, the electric motor reaches a preferred initial speed of 20 percent of the full operating speed. The motor speed then increases slowly in a linearly continuous fashion from 20 percent to 100 percent of full operating speed. This provides a smooth, soft start without jarring the transmission or the door or gate. The motor moves the barrier at maximum speed for the largest portion of its travel, after which the operator slowly decreases speed from 100 percent to 20 percent as the barrier approaches the limit of travel, providing a soft, smooth and quiet stop. A slow, smooth start and stop provides a safer barrier movement operator for the user because there is less momentum to apply an impulse force in the event of an obstruction. In a fast system, relatively high momentum of the door changes to zero at the obstruction before the system can actually detect the obstruction. This leads to the application of a high impulse force. With the system of the invention, a slower stop speed means the system has less momentum to overcome, and therefore a softer, more forgiving force reversal. A slow, smooth start and stop also provide a more aesthetically pleasing effect to the user, and when coupled with a quieter DC motor, a barrier movement operator which operates very quietly.  
           [0017]    The operator includes two relays and a pair of field effect transistors (FETs) for controlling the motor. The relays are used to control direction of travel. The FET's, with phase controlled, pulse width modulation, control start up and speed. Speed is responsive to the duration of the pulses applied to the FETs. A longer pulse causes the FETs to be on longer causing the barrier speed to increase. Shorter pulses result in a slower speed. This provides a very fine ramp control and more gentle starts and stops.  
           [0018]    The movable barrier operator provides for the automatic measurement and calculation of the total distance the door is to travel. The total door travel distance is the distance between the UP and the DOWN limits (which depend on the type of door). The automatic measurement of door travel distance is a measure of the length of the door. Since shorter doors must travel at slower speeds than normal doors (for safety reasons), this enables the operator to automatically adjust the motor speed so the speed of door travel is the same regardless of door size. The total door travel distance in turn determines the maximum speed at which the operator will travel. By determining the total distance traveled, travel speeds can be automatically changed without having to modify the hardware.  
           [0019]    The movable barrier operator provides full door or gate closure, i.e. a firm closure of the door to the floor so that the door is not movable in place after it stops. The operator includes a digital control or processor, specifically a microcontroller which has an internal microprocessor, an internal RAM and an internal ROM and an external EEPROM. The microcontroller executes instructions stored in its internal ROM and provides motor direction control signals to the relays and speed control signals to the FETs. The operator is first operated in a learn mode to store a DOWN limit position for the door. The DOWN limit position of the door is used as an approximation of the location of the floor (or as a minimum reversal point, below which no auto-reverse will occur). When the door reaches the DOWN limit position, the microcontroller causes the electric motor to drive the door past the DOWN limit a small distance, say for one or two inches. This causes the door to close solidly on the floor.  
           [0020]    The operator embodying the present invention provides variable door or gate output speed, i.e., the user can vary the minimum speed at which the motor starts and stops the door. This enables the user to overcome differences in door installations, i.e. stickiness and resistance to movement and other varying functional-type forces. The minimum barrier speeds in the UP and DOWN directions are determined by the user-configured force settings, which are adjusted using UP and DOWN force potentiometers. The force potentiometers set the lengths of the pulses to the FETs, which translate to variable speeds. The user gains a greater force output and a higher minimum starting speed to overcome differences in door installations, i.e. stickiness and resistance to movement and other varying functional-type forces speed, without affecting the maximum speed of travel for the door. The user can configure the door to start at a speed greater than a default value, say 20 percent. This greater start up and slow down speed is transferred to the linearly variable speed function in that instead of traveling at 20 percent speed, increasing to 100 percent speed, then decreasing to 20 percent speed, the door may, for instance, travel at 40 percent speed to 100 percent speed and back down to 40 percent speed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a perspective view of a garage having mounted within it a garage door operator embodying the present invention;  
         [0022]    [0022]FIG. 2 is an exploded perspective view of a head unit of the garage door operator shown in FIG. 1;  
         [0023]    [0023]FIG. 3 is an exploded perspective view of a portion of a transmission unit of the garage door operator shown in FIG. 1;  
         [0024]    [0024]FIG. 4 is a block diagram of a controller and motor mounted within the head unit of the garage door operator shown in FIG. 1;  
         [0025]    FIGS.  5 A- 5 D are a schematic diagram of the controller shown in block format in FIG. 4;  
         [0026]    FIGS.  6 A- 6 B are a flow chart of an overall routine that executes in a microprocessor of the controller shown in FIGS.  5 A- 5 D;  
         [0027]    FIGS.  7 A- 7 H are a flow chart of the main routine executed in the microprocessor;  
         [0028]    [0028]FIG. 8 is a flow chart of a set variable light shut-off timer routine executed by the microprocessor;  
         [0029]    FIGS.  9 A- 9 C are a flow chart of a hardware timer interrupt routine executed in the microprocessor;  
         [0030]    FIGS.  10 A- 10 C are a flow chart of a 1 millisecond timer routine executed in the microprocessor;  
         [0031]    FIGS.  11 A- 11 C are a flow chart of a 125 millisecond timer routine executed in the microprocessor;  
         [0032]    FIGS.  12 A- 12 B are a flow chart of a 4 millisecond timer routine executed in the microprocessor;  
         [0033]    FIGS.  13 A- 13 B are a flow chart of an RPM interrupt routine executed in the microprocessor;  
         [0034]    [0034]FIG. 14 is a flow chart of a motor state machine routine executed in the microprocessor;  
         [0035]    [0035]FIG. 15 is a flow chart of a stop in midtravel routine executed in the microprocessor;  
         [0036]    [0036]FIG. 16 is a flow chart of a DOWN position routine executed in the microprocessor;  
         [0037]    FIGS.  17 A- 17 C are a flow chart of an UP direction routine executed in the microprocessor;  
         [0038]    [0038]FIG. 18 is a flow chart of an auto-reverse routine executed in the microprocessor;  
         [0039]    [0039]FIG. 19 is a flow chart of an UP position routine executed in the microprocessor;  
         [0040]    FIGS.  20 A- 20 D are a flow chart of the DOWN direction routine executed in the microprocessor;  
         [0041]    [0041]FIG. 21 is an exploded perspective view of a pass point detector and motor of the operator shown in FIG. 2;  
         [0042]    [0042]FIG. 22A is a plan view of the pass point detector shown in FIG. 21; and  
         [0043]    [0043]FIG. 22B is a partial plan view of the pass point detector shown in FIG. 21. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0044]    Referring now to the drawings and especially to FIG. 1, a movable barrier or garage door operator system is generally shown therein and referred to by numeral  8 . The system  8  includes a movable barrier operator or garage door operator  10  having a head unit  12  mounted within a garage  14 . More specifically, the head unit  12  is mounted to a ceiling  15  of the garage  14 . The operator  10  includes a transmission  18  extending from the head unit  12  with a releasable trolley  20  attached. The releasable trolley  20  releasably connects an arm  22  extending to a single panel garage door  24  positioned for movement along a pair of door rails  26  and  28 .  
         [0045]    The system  8  includes a hand-held RF transmitter unit  30  adapted to send signals to an antenna  32  (see FIG. 4) positioned on the head unit  12  and coupled to a receiver within the head unit  12  as will appear hereinafter. A switch module  39  is mounted on the head unit  12 . Switch module  39  includes switches for each of the commands available from a remote transmitter or from an optional wall-mounted switch (not shown). Switch module  39  enables an installer to conveniently request the various learn modes during installation of the head unit  12 . The switch module  39  includes a learn switch, a light switch, a lock switch and a command switch, which are described below. Switch module  39  may also include terminals for wiring a pedestrian door state sensor comprising a pair of contacts  13  and  15  for a pedestrian door  11 , as well as wiring for an optional wall switch (not shown).  
         [0046]    The garage door  24  includes the pedestrian door  11 . Contact  13  is mounted to door  24  for contact with contact  15  mounted to pedestrian door  11 . Both contacts  13  and  15  are connected via a wire  17  to head unit  12 . As will be described further below, when the pedestrian door  11  is closed, electrical contact is made between the contacts  13  and  15  closing a pedestrian door circuit in the receiver in head unit  12  and signalling that the pedestriam door state is closed. This circuit must be closed before the receiver will permit other portions of the operator to move the door  24 . If circuit is open, indicating that the pedestrian door state is open, the system will not permit door  24  to move.  
         [0047]    The head unit  12  includes a housing comprising four sections: a bottom section  102 , a front section  106 , a back section  108  and a top section  110 , which are held together by screws  112  as shown in FIG. 2. Cover  104  fits into front section  106  and provides a cover for a worklight. External AC power is supplied to the operator  10  through a power cord  112 . The AC power is applied to a step-down transformer  120 . An electric motor  118  is selectively energized by rectified AC power and drives a sprocket  125  in sprocket assembly  124 . The sprocket  125  drives chain  144  (see FIG. 3). A printed circuit board  114  includes a controller  200  and other electronics for operating the head unit  12 . A cable  116  provides input and output connections on signal paths between the printed circuit board  114  and switch module  39 . The transmission  18 , as shown in FIG. 3, includes a rail  142  which holds chain  144  within a rail and chain housing  140  and holds the chain in tension to transfer mechanical energy from the motor to the door.  
         [0048]    A block diagram of the controller and motor connections is shown in FIG. 4. Controller  200  includes an RF receiver  80 , a microprocessor  300  and an EEPROM  302 . RF receiver  80  of controller  200  receives a command to move the door and actuate the motor either from remote transmitter  30 , which transmits an RF signal which is received by antenna  32 , or from a user command switch  250 . User command switch  250  can be a switch on switch panel  39 , mounted on the head unit, or a switch from an optional wall switch. Upon receipt of a door movement command signal from either antenna  32  or user switch  250 , the controller  200  sends a power enable signal via line  240  to AC hot connection  206  which provides AC line current to transformer  212  and power to work light  210 . Rectified AC is provided from rectifier  214  via line  236  to relays  232  and  234 . Depending on the commanded direction of travel, controller  200  provides a signal to either relay  232  or relay  234 . Relays  232  and  234  are used to control the direction of rotation of motor  118  by controlling the direction of current flow through the windings. One relay is used for clockwise rotation; the other is used for counterclockwise rotation.  
         [0049]    Upon receipt of the door movement command signal, controller  200  sends a signal via line  230  to power-control FET  252 . Motor speed is determined by the duration or length of the pulses in the signal to a gate electrode of FET  252 . The shorter the pulses, the slower the speed. This completes the circuit between relay  232  and FET  252  providing power to motor  118  via line  254 . If the door had been commanded to move in the opposite direction, relay  234  would have been enabled, completing the circuit with FET  252  and providing power to motor  118  via line  238 .  
         [0050]    With power provided, the motor  118  drives the output shaft  216  which provides drive power to transmission sprocket  125 . Gear reduction housing  260  includes an internal pass point system which sends a pass point signal via line  220  to controller  220  whenever the pass point is reached. The pass point signal is provided to controller  200  via current limiting resistor  226  to protect controller  200  from electrostatic discharge (ESD). An RPM interrupt signal is provided via line  224 , via current limiting resistor  228 , to controller  200 . Lead  222  provides a plus five volts supply for the Hall effect sensors in the RPM module. Commanded force is input by two force potentiometers  202 ,  204 . Force potentiometer  202  is used to set the commanded force for UP travel; force potentiometer  204  is used to set the commanded force for DOWN travel. Force potentiometers  202  and  204  provide commanded inputs to controller  200  which are used to adjust the length of the pulsed signal provided to FET  252 .  
         [0051]    The pass point for this system is provided internally in the motor  118 . Referring to FIG. 22, the pass point module  40  is attached to gear reduction housing  260  of motor  118 . Pass point module  40  includes upper plate  42  which covers the three internal gears and switch within lower housing  50 . Lower housing  50  includes recess  62  having two pins  61  which position switch assembly  52  in recess  62 . Housing  50  also includes three cutouts which are sized to support and provide for rotation of the three geared elements. Outer gear  44  fits rotatably within cutout  64 . Outer gear includes a smooth outer surface for rotating within housing  50  and inner gear teeth for rotating middle gear  46 . Middle gear  46  fits rotatably within inner cutout  66 . Middle gear  46  includes a smooth outer surface and a raised portion with gear teeth for being driven by the gear teeth of outer ring gear  44 . Inner gear  48  fits within middle gear  46  and is driven by an extension of shaft  216 . Rotation of the motor  118  causes shaft  216  to rotate and drive inner gear  48 .  
         [0052]    Outer gear  44  includes a notch  74  in the outer periphery. Middle gear includes a notch  76  in the outer periphery. Referring to FIG. 22A, rotation of inner gear  48  rotates middle gear  46  in the same direction. Rotation of middle gear  46  rotates outer gear  44  in the same direction. Gears  46  and  44  are sized such that pass point indications comprising switch release cutouts  74  and  76  line up only once during the entire travel distance of the door. As seen in FIG. 22A, when switch release cutouts  74  and  76  line up, switch  72  is open generating a pass point presence signal. The location where switch release cutouts  74  and  76  line up is the pass point. At all other times, at least one of the two gears holds switch  72  closed generating a signal indicating that the pass point has not been reached.  
         [0053]    The receiver portion  80  of controller  200  is shown in FIG. 5A. RF signals may be received by the controller  200  at the antenna  32  and fed to the receiver  80 . The receiver  80  includes variable inductor L 1  and a pair of capacitors C 2  and C 3  that provide impedance matching between the antenna  32  and other portions of the receiver. An NPN transistor Q 4  is connected in common-base configuration as a buffer amplifier. Bias to the buffer amplifier transistor Q 4  is provided by resistors R 2 , R 3 . The buffered RF output signal is supplied to a second NPN transistor Q 5 . The radio frequency signal is coupled to a bandpass amplifier  280  to an average detector  282  which feeds a comparator  284 . Referring to FIGS. 5C and 5B, the analog output signal A, B is applied to noise reduction capacitors C 19 , C 20  and C 21  then provided to pins P 32  and P 33  of the microcontroller  300 . Microcontroller  300  may be a Z86733 microprocessor.  
         [0054]    An external transformer  212  receives AC power from a source such as a utility and steps down the AC voltage to the power supply  90  circuit of controller  200 . Transformer  212  provides AC current to full-wave bridge circuit  214 , which produces a 28 volt full wave rectified signal across capacitor C 35 . The AC power may have a frequency of 50 Hz or 60 Hz. An external transformer is especially important when motor  118  is a DC motor. The 28 volt rectified signal is used to drive a wall control switch, a obstacle detector circuit, a door-in-door switch and to power FETs Q 11  and Q 12  used to start the motor. Zener diode D 18  protects against overvoltage due to the pulsed current, in particular, from the FETs rapidly switching off inductive load of the motor. The potential of the full-wave rectified signal is further reduced to provide 5 volts at capacitor C 38 , which is used to power the microprocessor  300 , the receiver circuit  80  and other logic functions.  
         [0055]    The 28 volt rectified power supply signal indicated by reference numeral T in FIG. 5C is voltage divided down by resistors R 61  and R 62 , then applied to an input pin P 24  of microprocessor  300 . This signal is used to provide the phase of the power line current to microprocessor  300 . Microprocessor  300  constantly checks for the phase of the line voltage in order to determine if the frequency of the line voltage is 50 Hz or 60 Hz. This information is used to establish the worklight time-out period and to select the look-up table stored in the ROM in the microcontroller for converting pulse width to door speed.  
         [0056]    When the door is commanded to move, either through a signal from a remote transmitter received through antenna  32  and processed by receiver  80 , or through an optional wall switch, the microprocessor  300  commands the work light to turn on. Microprocessor  300  sends a worklight enable signal from pin P 07 . The worklight enable signal is applied to the base of transistor Q 3 , which drives relay K 3 . AC power from a signal U provides power for operating the worklight  210 .  
         [0057]    Microprocessor  300  reads from and writes data to an EEPROM  302  via its pins P 25 , P 26  and P 27 . EEPROM  302  may be a 93C46. Microprocessor  300  provides a light enable signal at pin P 21  which is used to enable a learn mode indicator yellow LED D 15 . LED D 15  is enabled or lit when the receiver is in the learn mode. Pin P 26  provides double duty. When the user selects switch S 1 , a learn enable signal is provided to both microprocessor  300  and EEPROM  302 . Switch S 1  is mounted on the head unit  12  and is part of switch module  39 , which is used by the installer to operate the system.  
         [0058]    An optional flasher module provides an additional level of safety for users and is controlled by microprocessor  300  at pin P 22 . The optional flasher module is connected between terminals  308  and  310 . In the optional flasher module, after receipt of a door command, the microprocessor  300  sends a signal from P 22  which causes the flasher light to blink for 2 seconds. The door does not move during that 2 second period, giving the user notice that the door has been commanded to move and will start to move in 2 seconds. After expiration of the 2 second period, the door moves and the flasher light module blinks during the entire period of door movement. If the operator does not have a flasher module installed in the head unit, when the door is commanded to move, there is no time delay before the door begins to move.  
         [0059]    Microprocessor  300  provides the signals which start motor  116 , control its direction of rotation (and thus the direction of movement of the door) and the speed of rotation (speed of door travel). FETs Q 11  and Q 12  are used to start motor  118 . Microprocessor  300  applies a pulsed output signal to the gates of FETs Q 11  and Q 12 . The lengths of the pulses determine the time the FETs conduct and thus the amount of time current is applied to start and run the motor  118 . The longer the pulse, the longer current is applied, the greater the speed of rotation the motor  118  will develop. Diode D 11  is coupled between the 28 volt power supply and is used to clean up flyback voltage to the input bridge D 4  when the FETs are conducting. Similarly, Zener diode D 19  (see FIG. 5A) is used to protect against overvoltage when the FETs are conducting.  
         [0060]    Control of the direction of rotation of motor  118  (and thus direction of travel of the door) is accomplished with two relays, K 1  and K 2 . Relay K 1  supplies current to cause the motor to rotate clockwise in an opening direction (door moves UP); relay K 2  supplies current to cause the motor to rotate counterclockwise in a closing direction (door moves DOWN). When the door is commanded to move UP, the microprocessor  300  sends an enable signal from pin P 05  to the base of transistor Q 1 , which drives relay K 1 . When the door is commanded to move DOWN, the microprocessor  300  sends an enable signal from pin P 06  to the base of transistor Q 2 , which drives relay K 2 .  
         [0061]    Door-in-door contacts  13  and  15  are connected to terminals  304  and  306 . Terminals  304  and  306  are connected to relays K 1  and K 2 . If the signal between contacts  13  and  15  is broken, the signal across terminals  304  and  306  is open, preventing relays K 1  and K 2  from energizing. The motor  118  will not rotate and the door  24  will not move until the user closes pedestrian door  11 , making contact between contacts  13  and  15 .  
         [0062]    The pass point signal  220  from the pass point module  40  (see FIG. 21) of motor  118  is applied to pin P 23  of microprocessor  300 . The RPM signal  224  from the RPM sensor module in motor  118  is applied to pin P 31  of microprocessor  300 . Application of the pass point signal and the RPM signal is described with reference to the flow charts.  
         [0063]    An optional wall control, which duplicates the switches on remote transmitter  30 , may be connected to controller  200  at terminals  312  and  314 . When the user presses the door command switch  39 , a dead short is made to ground, which the microprocessor  300  detects by the failure to detect voltage. Capacitor C 22  is provided for RF noise reduction. The dead short to ground is sensed at pins P 02  and P 03 , for redundancy.  
         [0064]    Switches S 1  and S 2  are part of switch module  39  mounted on head unit  12  and used by the installer for operating the system. As stated above, S 1  is the learn switch. S 2  is the door command switch. When S 2  is pressed, microprocessor  300  detects the dead short at pins P 02  and P 03 .  
         [0065]    Input from an obstacle detector (not shown) is provided at terminal  316 . This signal is voltage divided down and provided to microprocessor  300  at pins P 20  and P 30 , for redundancy. Except when the door is moving and less than an inch above the floor, when the obstacle detector senses an object in the doorway, the microprocessor executes the auto-reverse routine causing the door to stop and/or reverse depending on the state of the door movement.  
         [0066]    Force and speed of door travel are determined by two potentiometers. Potentiometer R 33  adjusts the force and speed of UP travel; potentiometer R 34  adjusts the force and speed of DOWN travel. Potentiometers R 33  and R 34  act as analog voltage dividers. The analog signal from R 33 , R 34  is further divided down by voltage divider R 35 /R 37 , R 36 /R 38  before it is applied to the input of comparators  320  and  322 . Reference pulses from pins P 34  and P 35  of microprocessor  300  are compared with the force input from potentiometers R 33  and R 34  in comparators  320  and  322 . The output of comparators  320  and  322  is applied to pins P 01  and P 00 .  
         [0067]    To perform the A/D conversion, the microprocessor  300  samples the output of the comparators  320  and  322  at pins P 00  and P 01  to determine which voltage is higher: the voltage from the potentiometer R 33  or R 34  (IN) or the voltage from the reference pin P 34  or P 35  (REF). If the potentiometer voltage is higher than the reference, then the microprocessor outputs a pulse. If not, the output voltage is held low. The RC filter (R 39 , C 29 /R 40 , C 30 ) converts the pulses into a DC voltage equivalent to the duty cycle of the pulses. By outputting the pulses in the manner described above, the microprocessor creates a voltage at REF which dithers around the voltage at IN. The microprocessor then calculates the duty cycle of the pulse output which directly correlates to the voltage seen at IN.  
         [0068]    When power is applied to the head unit  12  including controller  200 , microprocessor  300  executes a series of routines. With power applied, microprocessor  300  executes the main routines shown in FIGS. 6A and 6B. The main loop  400  includes three basic functions, which are looped continuously until power is removed. In block  402  the microprocessor  300  handles all non-radio EEPROM communications and disables radio access to the EEPROM  302  when communicating. This ensures that during normal operation, i.e., when the garage door operator is not being programmed, the remote transmitter does not have access to the EEPROM, where transmitter codes are stored. Radio transmissions are processed upon receipt of a radio interrupt (see below).  
         [0069]    In block  404 , microprocessor  300  maintains all low priority tasks, such as calculating new force levels and minimum speed. Preferably, a set of redundant RAM registers is provided. In the event of an unforeseen event (e.g., an ESD event) which corrupts regular RAM, the main RAM registers and the redundant RAM registers will not match. Thus, when the values in RAM do not match, the routine knows the regular RAM has been corrupted. (See block  504  below.) In block  406 , microprocessor  300  tests redundant RAM registers. Several interrupt routines can take priority over blocks  402 ,  404  and  406 .  
         [0070]    The infrared obstacle detector generates an asynchronous IR interrupt signal which is a series of pulses. The absence of the obstacle detector pulses indicates an obstruction in the beam. After processing the IR interrupt, microprocessor  300  sets the status of the obstacle detector as unobstructed at block  416 .  
         [0071]    Receipt of a transmission from remote transmitter  30  generates an asynchronous radio interrupt at block  410 . At block  418 , if in the door command mode, microprocessor  300  parses incoming radio signals and sets a flag if the signal matches a stored code. If in the learn mode, microprocessor  300  stores the new transmitter codes in the EEPROM.  
         [0072]    An asynchronous interrupt is generated if a remote communications unit is connected to an optional RS-232 communications port located on the head unit. Upon receipt of the hardware interrupt, microprocessor  300  executes a serial data communications routine for transferring and storing data from the remote hardware.  
         [0073]    Hardware timer  0  interrupt is shown in block  422 . In block  422 , microprocessor  300  reads the incoming AC line signal from pin P 24  and handles the motor phase control output. The incoming line signal is used to determine if the line voltage is 50 Hz for the foreign market or 60 Hz for the domestic market. With each interrupt, microprocessor  300 , at block  426 , task switches among three tasks. In block  428 , microprocessor  300  updates software timers. In block  430 , microprocessor  300  debounces wall control switch signals. In block  432 , microprocessor  300  controls the motor state, including motor direction relay outputs and motor safety systems.  
         [0074]    When the motor  118  is running, it generates an asynchronous RPM interrupt at block  434 . When microprocessor  300  receives the asynchronous RPM interrupt at pin P 31 , it calculates the motor RPM period at block  436 , then updates the position of the door at block  438 .  
         [0075]    Further details of main loop  400  are shown in FIGS. 7A through 7H. The first step executed in main loop  400  is block  450 , where the microprocessor checks to see if the pass point has been passed since the last update. If it has, the routine branches to block  452 , where the microprocessor  300  updates the position of the door relative to the pass point in EEPROM  302  or non-volatile memory. The routine then continues at block  454 . An optional safety feature of the garage door operator system enables the worklight, when the door is open and stopped and the infrared beam in the obstacle detector is broken.  
         [0076]    At block  454 , the microprocessor checks if the enable/disable of the worklight for this feature has been changed. Some users want the added safety feature; others prefer to save the electricity used. If new input has been provided, the routine branches to block  456  and sets the status of the obstacle detector-controlled worklight in non-volatile memory in accordance with the new input. Then the routine continues to block  458  where the routine checks to determine if the worklight has been turned on without the timer. A separate switch is provided on both the remote transmitter  30  and the head unit at module  39  to enable the user to switch on the worklight without operating the door command switch. If no, the routine skips to block  470 .  
         [0077]    If yes, the routine checks at block  460  to see if the one-shot flag has been set for an obstacle detector beam break. If no, the routine skips to block  470 .. If yes, the routine checks if the obstacle detector controlled worklight is enabled at block  462 . If not, the routine skips to block  470 . If it is, the routine checks if the door is stopped in the fully open position at block  464 . If no, the routine skips to block  470 . If yes, the routine calls the SetVarLight subroutine (see FIG. 8) to enable the appropriate turn off time (4.5 minutes for 60 Hz systems or 2.5 minutes for 50 Hz systems). At block  468 , the routine turns on the worklight.  
         [0078]    At block  470 , the microprocessor  300  clears the one-shot flag for the infrared beam break. This resets the obstacle detector, so that a later beam break can generate an interrupt. At block  472 , if the user has installed a temporary password usable for a fixed period of time, the microprocessor  300  updates the non-volatile timer for the radio temporary password. At block  474 , the microprocessor  300  refreshes the RAM registers for radio mode from non-volatile memory (EEPROM  302 ). At block  476 , the microprocessor  300  refreshes I/O port directions, i.e., whether each of the ports is to be input or output. At block  478 , the microprocessor  300  updates the status of the radio lockout flag, if necessary. The radio lockout flag prevents the microprocessor from responding to a signal from a remote transmitter. A radio interrupt (described below) will disable the radio lockout flag and enable the remote transmitter to communicate with the receiver.  
         [0079]    At block  480 , the microprocessor  300  checks if the door is about to travel. If not, the routine skips to block  502 . If the door is about to travel, the microprocessor  300  checks if the limits are being trained at block  482 . If they are, the routine skips to block  502 . If not, the routine asks at block  484  if travel is UP or DOWN. If DOWN, the routine refreshes the DOWN limit from non-volatile memory (EEPROM  302 ) at block  486 . If UP, the routine refreshes the UP limit from non-volatile memory (EEPROM  302 ) at block  488 . The routine updates the current operating state and position relative to the pass point in non-volatile memory at block  490 . This is a redundant read for stability of the system.  
         [0080]    At block  492 , the routine checks for completion of a limit training cycle. If training is complete, the routine branches to block  494  where the new limit settings and position relative to the pass point are written to non-volatile memory.  
         [0081]    The routine then updates the counter for the number of operating cycles at block  496 . This information can be downloaded at a later time and used to determine when certain parts need to be replaced. At block  498  the routine checks if the number of cycles is a multiple of 256. Limiting the storage of this information to multiples of 256 limits the number of times the system has to write to that register. If yes it updates the history of force settings at block  500 . If not, the routine continues to block  502 .  
         [0082]    At block  502  the routine updates the learn switch debouncer. At block  504  the routine performs a continuity check by comparing the backup (redundant) RAM registers with the main registers. If they do not match, the routine branches to block  506 . If the registers do not match, the RAM memory has been corrupted and the system is not safe to operate, so a reset is commanded. At this point, the system powers up as if power had been removed and reapplied and the first step is a self test of the system (all installation settings are unchanged).  
         [0083]    If the answer to block  504  is yes, the routine continues to block  508  where the routine services any incoming serial messages from the optional wall control (serial messages might be user input start or stop commands). The routine then loads the UP force timing from the ROM look-up table, using the user setting as an index at block  510 . Force potentiometers R 33  and R 34  are set by the user. The analog values set by the user are converted to digital values. The digital values are used as an index to the look-up table stored in memory. The value indexed from the look-up table is then used as the minimum motor speed measurement. When the motor runs, the routine compares the selected value from the look-up table with the digital timing from the RPM routine to ensure the force is acceptable.  
         [0084]    Instead of calculating the force each time the force potentiometers are set, a look-up table is provided for each potentiometer. The range of values based on the range of user inputs is stored in ROM and used to save microprocessor processing time. The system includes two force limits: one for the UP force and one for the DOWN force. Two force limits provide a safer system. A heavy door may require more UP force to lift, but need a lower DOWN force setting (and therefore a slower closing speed) to provide a soft closure. A light door will need less UP force to open the door and possibly a greater DOWN force to provide a full closure.  
         [0085]    Next the force timing is divided by power level of the motor for the door to scale the maximum force timeout at block  512 . This step scales the force reversal point based on the maximum force for the door. The maximum force for the door is determined based on the size of the door, i.e. the distance the door travels. Single piece doors travel a greater distance than segmented doors. Short doors require less force to move than normal doors. The maximum force for a short door is scaled down to 60 percent of the maximum force available for a normal door. So, at block  512 , if the force setting is set by the user, for example at 40 percent, and the door is a normal door (i.e., a segmented door or multi-paneled door), the force is scaled to 40 percent of 100 percent. If the door is a short door (i.e., a single panel door), the force is scaled to 40 percent of 60 percent, or 24 percent.  
         [0086]    At block  514 , the routine loads the DOWN force timing from the ROM look-up table, using the user setting as an index. At block  516 , the routine divides the force timing by the power level of the motor for the door to scale the force to the speed.  
         [0087]    At block  518  the routine checks if the door is traveling DOWN. If yes, the routine disables use of the MinSpeed Register at block  524  and loads the MinSpeed Register with the DOWN force setting, i.e., the value read from the DOWN force potentiometer at block  526 . If not, the routine disables use of the MinSpeed Register at block  520  and loads the MinSpeed Register with the UP force setting from the force potentiometer at block  522 .  
         [0088]    The routine continues at block  528  where the routine subtracts 20 from the MinSpeed value. The MinSpeed value ranges from 0 to 63. The system uses 64 levels of force. If the result is negative at block  530 , the routine clears the MinSpeed Register at block  532  to effectively truncate the lower 38 percent of the force settings. If no, the routine divides the minimum speed by 4 to scale 8 speeds to 32 force settings at block  534 . At block  536 , the routine adds 4 into the minimum speed to correct the offset, and clips the result to a maximum of 12. At block  538  the routine enables use of the MinSpeed Register.  
         [0089]    At block  540  the routine checks if the period of the rectified AC line signal (input to microprocessor  300  at pin P 24 ) is less than 9 milliseconds (indicating the line frequency is 60 Hz). If it is, the routine skips to block  548 . If not, the routine checks if the light shut-off timer is active at block  542 . If not, the routine skips to block  548 . If yes, the routine checks if the light time value is greater than 2.5 minutes at block  544 . If no, the routine skips to block  548 . If yes, the routine calls the SetVarLight subroutine (see FIG. 8), to correct the light timing setting, at block  546 .  
         [0090]    At block  548  the routine checks if the radio signal has been clear for 100 milliseconds or more. If not, the routine skips to block  552 . If yes, the routine clears the radio at block  550 . At block  552 , the routine resets the watchdog timer. At block  554 , the routine loops to the beginning of the main loop.  
         [0091]    The SetVarLight subroutine, FIG. 8, is called whenever the door is commanded to move and the worklight is to be turned on. When the SetVarLight subroutine, block  558  is called, the subroutine checks if the period of the rectified power line signal (pin P 24  of microprocessor  300 ) is greater than or equal to 9 milliseconds. If yes, the line frequency is 50 Hz, and the timer is set to 2.5 minutes at block  564 . If no, the line frequency is 60 Hz and the timer is set to 4.5 minutes at block  562 . After setting, the subroutine returns to the call point at block  566 .  
         [0092]    The hardware timer interrupt subroutine operated by microprocessor  300 , shown at block  422 , runs every 0.256 milliseconds. Referring to FIGS.  9 A- 9 C, when the subroutine is first called, it sets the radio interrupt status as indicated by the software flags at block  580 . At block  582 , the subroutine updates the software timer extension. The next series of steps monitor the AC power line frequency (pin P 24  of microprocessor  300 ). At step  584 , the subroutine checks if the rectified power line input is high (checks for a leading edge). If yes, the subroutine skips to block  594 , where it increments the power line high time counter, then continues to block  596 . If no, the subroutine checks if the high time counter is below 2 milliseconds at block  586 . If yes, the subroutine skips to block  594 . If no, the subroutine sets the measured power line time in RAM at block  588 . The subroutine then resets the power line high time counter at block  590  and resets the phase timer register in block  592 .  
         [0093]    At block  596 , the subroutine checks if the motor power level is set at 100 percent. If yes, the subroutine turns on the motor phase control output at block  606 . If no, the subroutine checks if the motor power level is set at 0 percent at block  598 . If yes, the subroutine turns off the motor phase control output at block  604 . If no, the phase timer register is decremented at block  600  and the result is checked for sign. If positive the subroutine branches to block  606 ; if negative the subroutine branches to block  604 .  
         [0094]    The subroutine continues at block  608  where the incoming RPM signal (at pin P 31  of microprocessor  300 ) is digitally filtered. Then the time prescaling task switcher (which loops through 8 tasks identified at blocks  620 ,  630 ,  640 ,  650 ) is incremented at block  610 . The task switcher varies from 0 to 7. At block  612 , the subroutine branches to the proper task depending on the value of the task switcher.  
         [0095]    If the task switcher is at value 2 (this occurs every 4 milliseconds), the execute motor state machine subroutine is called at block  620 . If the task is value 0 or 4 (this occurs every 2 milliseconds), the wall control switches are debounced at block  630 . If the task value is 6 (this occurs every 4 milliseconds), the execute 4 ms timer subroutine is called at block  640 . If the task is value 1, 3, 5 or 7, the 1 millisecond timer subroutine is called at block  650 . Upon completion of the called subroutine, the 0.256 millisecond timer subroutine returns at block  614 .  
         [0096]    Details of the 1 ms timer subroutine (block  650 ) are shown in FIGS.  10 A- 10 C. When this subroutine is called, the first step is to update the A/D converters on the UP and DOWN force setting potentiometers (P 34  and P 35  of microprocessor  300 ) at block  652 . At block  654 , the subroutine checks if the A/D conversion (comparison at comparators  320  and  322 ) is complete. If yes, the measured potentiometer values are stored at block  656 . Then the stored values (which vary from 0 to 127) are divided by 2 to obtain the 64 level force setting at block  658 . If no, the subroutine decrements the infrared obstacle detector timeout timer at block  660 . In block  662 , the subroutine checks if the timer has reached zero. If no, the subroutine skips to block  672 . If yes, the subroutine resets the infrared obstacle detector timeout timer at block  664 . The flag setting for the obstacle detector signal is checked at block  666 . If no, the one-shot break flag is set at block  668 . If yes, the flag is set indicating the obstacle detector signal is absent at block  670 .  
         [0097]    At block  672 , the subroutine increments the radio time out register. Then the infrared obstacle detector reversal timer is decremented at block  674 . The pass point input is debounced at block  676 . The 125 millisecond prescaler is incremented at block  678 . Then the prescaler is checked if it has reached 63 milliseconds at block  680 . If yes, the fault blinking LED is updated at block  682 . If no, the prescaler is checked if it has reached 125 ms at block  684 . If yes, the 125 ms timer subroutine is executed at block  686 . If no, the routine returns at block  688 .  
         [0098]    The 125 millisecond timer subroutine (block  690 ) is used to manage the power level of the motor  118 . At block  692 , the subroutine updates the RS-232 mode timer and exits the RS-232 mode timer if necessary. The same pair of wires is used for both wall control switches and RS-232 communication. If RS-232 communication is received while in the wall control mode, the RS-232 mode is entered. If four seconds passes since the last RS-232 word was received, then the RS-232 timer times out and reverts to the wall control mode. At block  694  the subroutine checks if the motor is set to be stopped. If yes, the subroutine skips to block  716  and sets the motor's power level to 0 percent. If no, the subroutine checks if the pre-travel safety light is flashing at block  696  (if the optional flasher module has been installed, a light will flash for 2 seconds before the motor is permitted to travel and then flash at a predetermined interval during motor travel). If yes, the subroutine skips to block  716  and sets the motor's power level to 0 percent.  
         [0099]    If no, the subroutine checks if the microprocessor  300  is in the last phase of a limit training mode at block  698 . If yes, the subroutine skips to block  710 . If no, the subroutine checks if the microprocessor  300  is in another part of the limit training mode at block  700 . If no, the subroutine skips to block  710 . If yes, the subroutine checks if the minimum speed (as determined by the force settings) is greater than 40 percent at block  704 . If no, the power level is set to 40 percent at block  708 . If yes, the power level is set equal to the minimum speed stored in MinSpeed Register at block  706 .  
         [0100]    At block  710  the subroutine checks if the flag is set to slow down. If yes, the subroutine checks if the motor is running above or below minimum speed at block  714 . If above minimum speed, the power level of the motor is decremented one step increment (one step increment is preferably 5% of maximum motor speed) at block  722 . If below the minimum speed, the power level of the motor is incremented one step increment (which is preferably 5% of maximum motor speed) to minimum speed at block  720 .  
         [0101]    If the flag is not set to slow down at block  710 , the subroutine checks if the motor is running at maximum allowable speed at block  712 . If no, the power level of the motor is incremented one step increment (which is preferably 5% of maximum motor speed) at block  720 . If yes, the flag is set for motor ramp-up speed complete.  
         [0102]    The subroutine continues at block  724  where it checks if the period of the rectified AC power line (pin P 24  of microprocessor  300 ) is greater than or equal to 9 ms. If no, the subroutine fetches the motor's phase control information (indexed from the power level) from the 60 Hz look-up table stored in ROM at block  728 . If yes, the subroutine fetches the motor's phase control information (indexed from the power level) from the 50 Hz look-up table stored in ROM at block  726 .  
         [0103]    The subroutine tests for a user enable/disable of the infrared obstacle detector-controlled worklight feature at block  730 . Then the user radio learning timers, ZZWIN (at the wall keypad if installed) and AUXLEARNSW (radio on air and worklight command) are updated at block  732 . The software watchdog timer is updated at block  734  and the fault blinking LED is updated at block  736 . The subroutine returns at block  738 .  
         [0104]    The 4 millisecond timer subroutine is used to check on various systems which do not require updating as often as more critical systems. Referring to FIGS. 12A and 12B, the subroutine is called at block  640 . At block  750 , the RPM safety timers are updated. These timers are used to determine if the door has engaged the floor. The RPM safety timer is a one second delay before the operator begins to look for a falling door, i.e., one second after stopping. There are two different forces used in the garage door operator. The first type force are the forces determined by the UP and DOWN force potentiometers. These force levels determine the speed at which the door travels in the UP and DOWN directions. The second type of force is determined by the decrease in motor speed due to an external force being applied to the door (an obstacle or the floor). This programmed or pre-selected external force is the maximum force that the system will accept before an auto-reverse or stop is commanded.  
         [0105]    At block  752  the 0.5 second RPM timer is checked to see if it has expired. If yes, the 0.5 second timer is reset at block  754 . At block  756  safety checks are performed on the RPM seen during the last 0.5 seconds to prevent the door from falling. The 0.5 second timer is chosen so the maximum force achieved at the trolley will reach 50 kilograms in 0.5 seconds if the motor is operating at 100 percent of power.  
         [0106]    At block  758 , the subroutine updates the 1 second timer for the optional light flasher module. In this embodiment, the preferred flash period is 1 second. At block  760  the radio dead time and dropout timers are updated. At block  762  the learn switch is debounced. At block  764  the status of the worklight is updated in accordance with the various light timers. At block  766  the optional wall control blink timer is updated. The optional wall control includes a light which blinks when the door is being commanded to auto-reverse in response to an infrared obstacle detector signal break. At block  768  the subroutine returns.  
         [0107]    Further details of the asynchronous RPM signal interrupt, block  434 , are shown in FIGS. 13A and 13B. This signal, which is provided to microprocessor  300  at pin P 31 , is used to control the motor speed and the position detector. Door position is determined by a value relative to the pass point. The pass point is set at 0. Positions above the pass point are negative; positions below the pass point are positive. When the door travels to the UP limit, the position detector (or counter) determines the position based on the number of RPM pulses to the UP limit number. When the door travels DOWN to the DOWN limit, the position detector counts the number of RPM pulses to the DOWN limit number. The UP and DOWN limit numbers are stored in a register.  
         [0108]    At block  782  the RPM interrupt subroutine calculates the period of the incoming RPM signal. If the door is traveling UP, the subroutine calculates the difference between two successive pulses. If the door is traveling DOWN, the subroutine calculates the difference between two successive pulses. At block  784 , the subroutine divides the period by 8 to fit into a binary word. At block  786  the subroutine checks if the motor speed is ramping up. This is the max force mode. RPM timeout will vary from 10 to 500 milliseconds. Note that these times are recommended for a DC motor. If an AC motor is used, the maximum time would be scaled down to typically 24 milliseconds. A 24 millisecond period is slower than the breakdown RPM of the motor and therefore beyond the maximum possible force of most preferred motors. If yes, the RPM timeout is set at 500 milliseconds (0.5 seconds) at block  790 . If no, the subroutine sets the RPM timeout as the rounded-up value of the force setting in block  788 .  
         [0109]    At block  792  the subroutine checks for the direction of travel. This is found in the state machine register. If the door is traveling DOWN, the position counter is incremented at block  796  and the pass point debouncer is sampled at block  800 . At block  804 , the subroutine checks for the falling edge of the pass point signal. If the falling edge is present, the subroutine returns at block  814 . If there is a pass point falling edge, the subroutine checks for the lowest pass point (in cases where more than one pass point is used). If this is not the lowest pass point, the subroutine returns at block  814 . If it is the only pass point or the lowest pass point, the position counter is zeroed and the subroutine returns at block  814 .  
         [0110]    If the door is traveling UP, the subroutine decrements the position counter at block  794  and samples the pass point debouncer at block  798 . Then it checks for the rising edge of the pass point signal at block  802 . If there is no pass point signal rising edge, the subroutine returns at block  814 . If there is, it checks for the lowest pass point at block  806 . If no the subroutine returns at block  814 . If yes, the subroutine zeroes the position counter and returns at block  814 .  
         [0111]    The motor state machine subroutine, block  620 , is shown in FIG. 14. It keeps track of the state of the motor. At block  820 , the subroutine updates the false obstacle detector signal output, which is used in systems that do not require an infrared obstacle detector. At block  822 , the subroutine checks if the software watchdog timer has reached too high a value. If yes, a system reset is commanded at block  824 . If no, at block  826 , it checks the state of the motor stored in the motor state register located in EEPROM  302  and executes the appropriate subroutine.  
         [0112]    If the door is traveling UP, the UP direction subroutine at block  832  is executed. If the door is traveling DOWN, the DOWN direction subroutine is executed at block  828 . If the door is stopped in the middle of the travel path, the stop in midtravel subroutine is executed at block  838 . If the door is fully closed, the DOWN position subroutine is executed at block  830 . If the door is fully open, the UP position subroutine is executed at block  834 . If the door is reversing, the auto-reverse subroutine is executed at block  836 .  
         [0113]    When the door is stopped in midtravel, the subroutine at block  838  is called, as shown in FIG. 15. In block  840  the subroutine updates the relay safety system (ensuring that relays K 1  and K 2  are open). The subroutine checks for a received wall command or radio command. If there is no received command, the subroutine updates the worklight status and returns. If yes, the motor power is set to  20  percent at block  844  and the motor state is set to traveling DOWN at block  846 . The worklight status is updated and the subroutine returns at block  850 . If the door is stopped in midtravel and a door command is received, the door is set to close. The next time the system calls the motor state machine subroutine, the motor state machine will call the DOWN direction subroutine. The door must close to the DOWN limit before it can be opened to the full UP limit.  
         [0114]    If the state machine indicates the door is in the DOWN position (i.e. the DOWN limit position), the DOWN position subroutine, block  830 , at FIG. 16 is called. When the door is in the DOWN position, the subroutine checks if a wall control or radio command has been received. If no, the subroutine updates the light and returns at block  858 . If yes, the motor power is set to  20  percent at block  854  and the motor state register is set to show the state is traveling UP at block  856 . The subroutine then updates the light and returns at block  858 .  
         [0115]    The UP direction subroutine, block  832 , is shown in FIGS.  17 A- 17 C. At block  860  the subroutine waits until the main loop refreshes the UP limit from EEPROM  302 . Then it checks if 40 milliseconds have passed since closing of the light relay K 3  at block  862 . If not, the subroutine returns. If yes, the subroutine checks for flashing the warning light prior to travel at block  866  (only if the optional flasher module is installed). If the light is flashing, the status of the blinking light is updated and the subroutine returns at block  868 . If not, the flashing is terminated, the motor UP relay is turned on at block  870 . Then the subroutine waits until 1 second has passed after the motor was turned on at block  872 . If no, the subroutine skips to block  888 . If yes, the subroutine checks for the RPM signal timeout. If no, the subroutine checks if the motor speed is ramping up at block  876  by checking the value of the RAMPFLAG register in RAM (i.e., UP, DOWN, FULLSPEED, STOP). If yes, the subroutine skips to block  888 . If no, the subroutine checks if the measured RPM is longer than the allowable RPM period at block  878 . If no, the subroutine continues at block  888 .  
         [0116]    If the RPM signal has timed out at block  874  or the measured time period is longer than allowable at block  878 , the subroutine branches to block  880 . At block  880 , the reason is set as force obstruction. At block  882 , if the training limits are being set, the training status is updated. At block  884  the motor power is set to zero and the state is set as stopped in midtravel. At block  886  the subroutine returns.  
         [0117]    At block  888  the subroutine checks if the door's exact position is known. If it is not, the door's distance from the UP limit is updated in block  890  by subtracting the UP limit stored in RAM from the position of the door also stored in RAM. Then the subroutine checks at block  892  if the door is beyond its UP limit. If yes, the subroutine sets the reason as reaching the limit in block  894 . Then the subroutine checks if the limits are being trained. If yes, the limit training machine is updated at block  898 . If no, the motor's power is set as zero and the motor state is set at the UP position in block  900 . Then the subroutine returns at block  902 .  
         [0118]    If the door is not beyond its UP limit, the subroutine checks if the door is being manually positioned in the training cycle at block  904 . If not, the door position within the slowdown distance of the limit is checked at block  906 . If yes, the motor slow down flag is set at block  910 . If the door is being positioned manually at block  904  or the door is not within the slow down distance, the subroutine skips to block  912 . At block  912  the subroutine checks if a wall control or radio command has been received. If yes, the motor power is set at zero and the state is set at stopped in midtravel at block  916 . If no, the system checks if the motor has been running for over 27 seconds at block  914 . If yes, the motor power is set at zero and the motor state is set at stopped in midtravel at block  916 . Then the subroutine returns at block  918 .  
         [0119]    Referring to FIG. 18, the auto-reverse subroutine block  836  is described. (Force reversal is stopping the motor for 0.5 seconds, then traveling UP.) At block  920  the subroutine updates the 0.5 second reversal timer (the force reversal timer described above). Then the subroutine checks at block  922  for expiration of the force-reversal timer. If yes, the motor power is set to 20 percent at block  924  and the motor state is set to traveling UP at block  926  and the subroutine returns at block  932 . If the timer has not expired, the subroutine checks for receipt of a wall command or radio command at block  928 . If yes, the motor power is set to zero and the state is set at stopped in midtravel at block  930 , then the subroutine returns at block  932 . If no, the subroutine returns at block  932 .  
         [0120]    The UP position routine, block  834 , is shown in FIG. 19. Door travel limits training is started with the door in the UP position. At block  934 , the subroutine updates the relay safety system. Then the subroutine checks for receipt of a wall command or radio command at block  936  indicating an intervening user command. If yes, the motor power is set to 20 percent at block  938  and the state is set at traveling DOWN in block  940 . Then the light is updated and the subroutine returns at block  950 . If no wall command has been received, the subroutine checks for training the limits at block  942 . If no, the light is updated and the subroutine returns at block  950 . If yes, the limit training state machine is updated at block  944 . Then the subroutine checks if it is time to travel DOWN at block  946 . If no, the subroutine updates the light and returns at block  950 . If it is time to travel DOWN, the state is set at traveling DOWN at block  948  and the system returns at block  950 .  
         [0121]    The DOWN direction subroutine, block  828 , is shown in FIGS.  20 A- 20 D. At block  952 , the subroutine waits until the main loop routine refreshes the DOWN limit from EEPROM  302 . For safety purposes, only the main loop or the remote transmitter (radio) can access data stored in or written to the EEPROM  302 . Because EEPROM communication is handled within software, it is necessary to ensure that two software routines do not try to communicate with the EEPROM at the same time (and have a data collision). Therefore, EEPROM communication is allowed only in the Main Loop and in the Radio routine, with the Main loop having a busy flag to prevent the radio from communicating with the EEPROM at the same time. At block  954 , the subroutine checks if 40 milliseconds has passed since closing of the light relay K 3 . If no, the subroutine returns at block  956 . If yes, the subroutine checks if the warning light is flashing (for 2 seconds if the optional flasher module is installed) prior to travel at block  958 . If yes, the subroutine updates the status of the flashing light and returns at block  960 . If no, or the flashing is completed, the subroutine turns on the DOWN motor relay K 2  at block  962 . At block  964  the subroutine checks if one second has passed since the motor is first turned on. The system ignores the force on the motor for the first one second. This allows the motor time to overcome the inertia of the door (and exceed the programmed force settings) without having to adjust the programmed force settings for ramp up, normal travel and slow down. Force is effectively set to maximum during ramp up to overcome sticky doors.  
         [0122]    If the one second time has not passed, the subroutine skips to block  984 . If the one second time limit has passed, the subroutine checks for the RPM signal time out at block  966 . If no, the subroutine checks if the motor speed is currently being ramped up at block  968  (this is a maximum force condition). If yes, the routine skips to block  984 . If no, the subroutine checks if the measured RPM period is longer than the allowable RPM period. If no, the subroutine continues at block  984 .  
         [0123]    If either the RPM signal has timed out (block  966 ) or the RPM period is longer than allowable (block  970 ), this is an indication of an obstruction or the door has reached the DOWN limit position, and the subroutine skips to block  972 . At block  972 , the subroutine checks if the door is positioned beyond the DOWN limit setting. If it is, the subroutine skips to block  990  where it checks if the motor has been powered for at least one second. This one second power period after the DOWN limit has been reached provides for the door to close fully against the floor. This is especially important when DC motors are used. The one second period overcomes the internal braking effect of the DC motor on shut-off. Auto-reverse is disabled after the position detector reaches the DOWN limit.  
         [0124]    If the motor has been running for one second, at block  990 , the subroutine sets the reason as reaching the limit at block  994 . The subroutine then checks if the limits are being trained at block  998 . If yes, the limit training machine is updated at block  1002 . If no, the motor's power is set to zero and the motor state is set at the DOWN position in block  1006 . In block  1008  the subroutine returns.  
         [0125]    If the motor has not been running for at least one second at block  990 , the subroutine sets the reason as early limit at block  1026 . Then the subroutine sets the motor power at zero and the motor state as auto-reverse at block  1028  and returns at block  1030 .  
         [0126]    Returning to block  984 , the subroutine checks if the door's position is currently unknown. If yes, the subroutine skips to block  1004 . If no, the subroutine updates the door's distance from the DOWN limit using internal RAM in microprocessor  300  in block  986 . Then the subroutine checks at block  988  if the door is three inches beyond the DOWN limit. If yes, the subroutine skips to block  990 . If no, the subroutine checks if the door is being positioned manually in the training cycle at block  992 . If yes, the subroutine skips to block  1004 . If no, the subroutine checks if the door is within the slow DOWN distance of the limit at block  996 . If no, the subroutine skips to block  1004 . If yes, the subroutine sets the motor slow down flag at block  1000 .  
         [0127]    At block  1004 , the subroutine checks if a wall control command or radio command has been received. If yes, the subroutine sets the motor power at zero and the state as auto-reverse at block  1012 . If no, the subroutine checks if the motor has been running for over 27 seconds at block  1010 . If yes, the subroutine sets the motor power at zero and the state at auto-reverse. If no, the subroutine checks if the obstacle detector signal has been missing for 12 milliseconds or more at block  1014  indicating the presence of the obstacle or the failure of the detector. If no, the subroutine returns at block  1018 . If yes, the subroutine checks if the wall control or radio signal is being held to override the infrared obstacle detector at block  1016 . If yes, the subroutine returns at block  1018 . If no, the subroutine sets the reason as infrared obstacle detector obstruction at block  1020 . The subroutine then sets the motor power, at zero and the state as auto-reverse at block  1022  and returns at block  1024 . (The auto-reverse routine stops the motor for 0.5 seconds then causes the door to travel up.)  
         [0128]    The appendix attached hereto includes a source listing of a series of routines used to operate a movable barrier operator in accordance with the present invention.  
         [0129]    While there has been illustrated and described a particular embodiment of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which followed in the true spirit and scope of the present invention.