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The present design relates to a manually operated switch such as a wall-mounted light switch for controlling the level of light intensity from a light fixture and more particularly to a light level controller actuated by the switch which includes a microcontroller for initiating control programs to regulate the level of light intensity.
Wall mounted light switches which include a dimmer have become increasingly popular especially for residential applications where it is desired to precisely control the level of light intensity in a particular room. Such light switches usually include a variable resistor which is manually manipulated to control the voltage input to the light, where the variable resistor is connected in series with the household AC power line. A desirable feature in such switches would be the ability to return to predetermined levels of light intensity from conditions of either full power on or full power off. At present, however, such switches have no such memory and formerly established light intensity levels may be reestablished only by manual operation and guesswork.
There are in existence, however, touch actuated dimmer controls which cycle through a dim to a bright cycle and back again, and include a memory function such that removing the hand from the switch will stop the cycle and store the level of light intensity at that point in memory. A subsequent touch will turn the light off and yet a further touch will return the light to its previous intensity level based upon the value of the intensity level stored in memory. While an improvement over the manually-operated variable-resistor type of dimmer, this dimmer may require the user to manually cycle through a complete cycle of dim light to bright light to arrive at a desired intensity level. This latter switch is known as a DECORA.RTM. touch dimmer and is manufactured by Leviton Manufacturing Company, Inc. of Littleneck, N.Y. The DECORA.RTM. touch dimmer, however, lacks the versatility needed for certain aesthetic effects such as an automatic gradual fade from one light level to another.
Moreover, it cannot change the direction, that is, either the increasing (up) or the decreasing (down), of light intensity from one direction to another without completing a full cycle from dim to bright and back again. Also, the touch dimmer has no "remote" capability that would enable one to use its features from a remote location such as a hallway or another room. Full function remotes are common with ordinary two-position light switches, but have not been available for dimmers because of the complexity of the circuitry.
Design of the microcontroller controlled light dimmer
The present design provides a highly versatile microcontroller controlled light level intensity switch which is operated by a pair of non-latching switches which provide inputs to the microcontroller. The non-latching switches may be arranged as upper and lower switches on a rocker panel or independent pair of panels which are normally biased to remain in a neutral position. The switches are each connected in series with the AC mains power line so that when either switch is depressed a signal in the form of a series of sequential pulses is provided to the microcontroller.
When the switch is depressed in either the up or down direction, the microcontroller first determines whether the depression of the switch is momentary, that is, a brief tap, or whether it is being held down for a period of more than transitory duration. When the switch is held, the microcontroller advances the level of light intensity in the direction indicated by the switch, that is, either towards bright or towards dim. When the switch is subsequently released the microcontroller stores that current level of light intensity as a "preset" level in its memory. If the switch is first tapped in either direction with the light intensity at some static level the microcontroller will cause the level of light intensity to automatically advance or "fade" towards a predetermined level, either "full on," "off," or "preset."
The fade may occur at a rate which can be programmed in the microcontroller. If desired, the speed of the fade may vary depending upon whether the fade is from dim to bright or vice versa. For example, it is possible to program all downward fades to occur more gradually than all upward fades. If the switch is tapped again while the light intensity is fading towards the preset level, the microcontroller will halt the fade and cause the light intensity level to abruptly shift to the preset level. If the "up" switch is tapped with light at the preset level, the light intensity will fade to full maximum.
If it is tapped in the downward position when the light intensity level is at the preset position the light intensity will fade towards zero. Thus, the microcontroller interprets the character of the command, that is, a hold or a tap, determines the current control mode, and initiates a light intensity control function accordingly. The three types of programs are preset, automatic fade, and abrupt transition.
The non-latching switches provide a pulse input, which is derived from the AC power source, to the light switch through a clamp and half-wave rectifying network. Thus, the input to the microcontroller is a series of square wave pulses. The microcontroller has an internal program which counts the number of a sequential series of pulses to determine if the switch is being tapped or held and executes a control program mode accordingly.
The microcontroller is connected to a source of light such as an incandescent light bulb of between 40 and 2,000 watts by means of a thyristor solid state switch. The thyristor controls power to the incandescent light source by turning on at a predetermined phase angle relative to the phase of the AC line source. For this purpose the thyristor is responsive to a timed firing signal generated by the microcontroller according to the program in operation.
The firing signal is synchronized with the incoming power supply line by a zero crossing detector which detects the transition in the AC power line from positive to negative. The microcontroller receives the zero crossing information and synchronizes this information with its internal clock which controls the timing of the firing signal for the thyristor. In this way the timing of the thyristor firing signal is calibrated to the desired level of light intensity and represents a phase angle at which the AC line is gated into the incandescent light source.
When either the "up" or "down" switch is held the computer first determines the current level of light intensity. The microcontroller then causes the level of light intensity to increase for "up" or decrease for "down" in predetermined increments by initiating thyristor firing signals which either advance the phase gating of the AC wave or retard it. As long as either switch is held "on," the level of light intensity will gradually advance or decline. Each time an additional increment of light intensity is added it replaces the current level in the memory which continues to be sampled in a closed-loop fashion until the switch is released. When the switch is released the current level of light intensity is stored in memory as a "preset" level.
When either switch is tapped the microcontroller interrogates memory to find out if the current level is equal to the preset level. This determines whether a fade is in progress or whether the light intensity is not changing. The subsequent control modes, "fade" and "abrupt transition," then depend upon whether the new level in memory is preset, full on, or full off, and whether the current level is higher than, lower than, or equal to this level.
The switches are wired in line with the main 120-volt AC line. Since the switches are at all times either "on" or "off" and there are no variable resistors used for the dimming function, a parallel set of remote switches, also wired in line with the AC line, may be provided to give full remote capability. Thus, another switch box may be provided in a hallway or adjacent room which fully duplicates the functions of the primary switch box without the necessity for duplication of the microcontroller and its associated circuitry. The remote switches are wired in parallel with the primary switches through their wall-mounted switch box forming a second parallel input to the microcontroller.
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