Patent Application
20070171647
This disclosure relates generally to control systems, and more particularly, to control systems used to control various features of illuminated product display cases.
Commercial retailers frequently display their wares on shelves in display cases. Often, these display cases are fitted with light sources that direct light toward to the display case shelves, thereby illuminating the products being offered for sale. Frequently, the light sources are fluorescent lamps, which are more energy efficient that incandescent lamps.
Sometimes display cases are also refrigerated, for example, as used in markets, restaurants, food vending operations, liquor stores and other locations, to preserve freshness as well as providing an attractive display of products to the consumer. Typically, refrigerated display cases have a enclosure with an opening that is sealed by a door that the consumer can easily open to retrieve the desired product.
Of course, the energy required to operate such refrigerated display cases can be substantial, and providing interior display lighting only adds to this need. For example, fluorescent lamps require the excitement of gases, which can generate heat up to approximately 100° F. to produce a maximum light output.
Thus, it is certainly desirable to improve the efficiency of any such display case system by reducing the amount of energy consumed, and likewise, reduce the amount of heat generated unnecessarily by product illumination systems, particularly in refrigerated display cases.
A control system is disclosed for use with an LED illumination system of the type used in a commercial display case. In several embodiments, the display case includes a sensor that is used as either a switch or as a controller to adjust the amount of power being provided to the LED's. Alternatively, a timer may be used as a control function. A number of control or switching techniques may be employed to provide for an efficient lighting control scheme.
The invention may be more readily understood by referring to the accompanying drawings in which:
Like numerals refer to like parts throughout the several views of the drawings.
This disclosure relates to the use of control systems to monitor and control selected features of an illuminated display case system. Although preferred embodiments are described below, it should be understood that various modifications can be accomplished within the parameters of the present invention.
Referring now to
Light sources 31 are affixed to the frame 14 inside the display case 10 to provide illumination for items 18 stocked on shelves 20. As better illustrated in
Advantageously, the use of LED's as a lighting source provides virtually instantaneous turn on for lighting. This feature can be combined with well known control techniques to provide improved efficiency and reduced costs in a large number of different possible ways. For example, a number of advantages can be realized by routinely dimming or turning off the LED's through a control scheme, including: (1) lower energy costs; (2) longer lamp life; (3) lower maintenance costs; and (4) reduced equipment wear. This can be a marketing advantage in restricted markets where the availability of energy is limited due to regulation, consumption, or other reason.
For example, as shown in
The enclosure 44 preferably includes a self-contained controller 45 available off the shelf, and suitable for providing some degree of control or adjustment over the feature being controlled, such as on/off control to the LED power. As used herein, the term “control” should be construed broadly to refer to any type of scheme that is useful for monitoring a system parameter and providing some degree of adjustment, either manual or automatic, to a controlled feature, such as voltage or current, for example.
In a first embodiment, the sensor 40 is a light meter that senses the ambient light level inside the display case10. For example, Extech Instruments Corporation makes a number of light meters that include a PC interface. A control scheme is implemented wherein the light meter is coupled to the controller 45, and wherein the amount of ambient light inside the display case 10 which is detected by the light meter determines how much voltage to provide to the light sources 31. In a simple arrangement, the light meter is coupled to a programmable controller. The use of a dimming circuit is advantageous since it is not necessary to have the light level of a retail display operating at maximum brightness all the time. There may be times during the day, given a good location, when the amount of daylight present in a store location is sufficient such that it would be acceptable to reduce the amount of artificial illumination provided to the product in the display case. Since reduction in illumination goes hand in hand with a reduction in power consumption, use of dimming results in an operating cost savings for the store owner.
For example, if amount of lumens detected by the light meter falls below a minimum level L1, then full voltage is provided to the light sources 31 in order to obtain full illumination. If the amount of lumens detected by the light meter is between the minimum level L1 and a preset level L2, then half the normal voltage is provided to the light sources 31. If the amount of lumens detected by the light meter exceeds preset level L2, then the voltage is set to 0. The design of a controller using a simple logic scheme with a conventional dimmer circuit is within the skill of the artisan. An alternative control scheme would set the voltage to a level that is inversely proportional to the amount of lumens detected by the light meter.
Advantageously, the dimming circuit may be implemented to provide manual or automatic control. In manual operation, input from the light meter is bypassed, for example, by turning a bypass switch on the controller. The operator then manually adjusts the LED controls to set a desired light level. In automatic operation, the bypass switch is returned to the normal position, and the control circuitry is designed to automatically adjust the LED light level in response to one or more input sources.
In a second embodiment, the sensor 40 is an occupancy sensor. Since there is no need for an illuminated display when there are no customers observing the display case, a control scheme is implemented wherein the lack of motion detected by the sensor 40 causes voltage to the light sources 31 to be reduced or cut entirely. For example, the sensor may be set to detect motion or occupancy within 15 feet of the door 12. If nothing is detected for 60 seconds, for example, the power to the light sources 31 is reduced to half. If the condition persists, and nothing is detected to 240 seconds, for example, then the power to the light sources is cut off. When motion is finally detected, the light sources 31 are again provided with full power. In this embodiment, the controller 45 may be a Watt Stopper FS-PP controller or similar, and the motion sensor may be an infrared (optical) device, such as the Watt Stopper HB-100-1 sensor or similar.
In a third embodiment, the sensor 40 is a temperature sensor such as a simple thermocouple or bayonet sensor made by Thermometric Corporation, or similar. For example, if there is a malfunction in the refrigerated display case, and the temperature rises, the presence of lighting inside the case will add to the problem. Therefore, a control scheme is implemented wherein voltage to the light sources 31 is shut off when the sensor detects that the temperature inside the display case exceeds a predetermined temperature T1. This condition could also be used to trip an alarm. When the temperature inside the display case returns to acceptable levels, the light sources 31 are provided with power.
In a fourth embodiment there is no sensor, but the controller 45 includes a timer, and most programmable controllers included a programmable timer function. A control scheme is implemented wherein voltage to the light sources 31 is provided in accord with a schedule programmed in the timer. For example, the timer may be set to provide voltage only during regular store hours.
A simple block diagram of a control system in accord with the present invention is shown in
Several well known circuit methods could be used to change or adjust the power consumption, such as (1) reduce the current using a current controlled circuit; (2) reduce the voltage using a constant voltage circuit; and (3) switching circuits by adding and subtracting active LED regions. Each of these techniques is well known to the artisan and a detailed explanation thereof is deemed unnecessary.
These and other well known control techniques may be used either alone or in combination to provide a suitable control scheme. For example, pulse width modulation is a preferred and well known power supply method to maximize life and efficiency of LED lighting sources. Voltage or current adjustment is also possible, but is less preferred. The use of a ramp up or ramp down time for the dimming circuit to change the light level from minimum to maximum and visa versa can be adjusted, from an instantaneous on time, to a ramp up time of several seconds, depending on adjustment and preference by store owner.
