US-20260129732-A1 - DYNAMIC THRESHOLDING FOR AMBIENT LIGHT-BASED LOAD CONTROL

US20260129732A1US 20260129732 A1US20260129732 A1US 20260129732A1US-20260129732-A1

Abstract

Approaches for controlling supply of power to a load in an environment based on ambient light sensing and dynamic thresholding include, based on an ambient light level in the environment decreasing to a turn-on threshold light level, controlling a switch of an electrical load controller to couple the supply of electrical power to the lighting load, sensing a current ambient light level in the environment after lapse of a predetermined amount of time subsequent to controlling the switch to couple the supply of electrical power to the lighting load, and adjusting a turn-off threshold light level using the current ambient light level.

Inventors

Brian Anthony YOKUM
Ronald James GUMINA

Assignees

LEVITON MANUFACTURING CO., INC.

Dates

Publication Date: 20260507
Application Date: 20260105

Claims (20)

1 . An electrical load controller for controlling conduction of a supply of electrical power to a lighting load in an environment, the electrical load controller including: a line input terminal and a load output terminal, the line input terminal configured to be electrically coupled to the supply of electrical power, and the load output terminal configured to be electrically coupled to the lighting load; a switch electrically coupled in series between the line input terminal and the load output terminal, the switch being controllable to selectively couple the supply of electrical power to the lighting load and decouple the supply of electrical power from the lighting load; and a processing circuit configured to perform: maintaining a light/dark state indicating a current ambient condition of the environment as being either daytime or nighttime; maintaining a first timer that dictates a minimum amount of time to lapse between consecutive transitions of the switch between coupling the supply of electrical power to the lighting load and decoupling the supply of electrical power from the lighting load; maintaining a second timer that dictates an amount of time to lapse, after controlling the switch to couple the supply of electrical power to the lighting load, before setting a turn-off threshold light level; and iteratively performing, over multiple iterations: determining a representative current ambient light level based at least in part on sensed current ambient light level sensed by one or more sensors; and adjusting the first timer and the second timer.
2 . The electrical load controller of claim 1 , wherein the iteratively performing further includes determining whether the first timer has lapsed, and wherein the processing circuit is further configured to perform: based on determining at an iteration of the multiple iterations that the first timer has lapsed, determining a current ambient condition as indicated by the light/dark state.
3 . The electrical load controller of claim 2 , wherein the processing circuit is further configured to perform at the iteration, based on determining that the current ambient condition is daytime: determining whether the representative current ambient light level has decreased to a turn-on threshold light level.
4 . The electrical load controller of claim 3 , wherein the processing circuit is further configured to perform at the iteration, based on determining that the representative current ambient light level has decreased to the turn-on threshold light level: setting the light/dark state to indicate the ambient condition as nighttime; and controlling the switch to couple the supply of electrical power to the lighting load; wherein based on controlling the switch to couple the supply of electrical power to the lighting load, the adjusting includes resetting the first timer and the second timer.
5 . The electrical load controller of claim 4 , wherein the processing circuit is further configured to perform, at a subsequent iteration of the multiple iterations, and based on the second timer lapsing, adjusting the turn-off threshold light level using the representative current ambient light level determined at the subsequent iteration, wherein the adjusting the turn-off threshold light level sets the turn-off threshold light level to be higher than the representative current ambient light level such that ambient light level in the environment must be brighter than the representative current ambient level for the processing circuit to control the switch to couple the supply of electrical power to the lighting load.
6 . The electrical load controller of claim 5 , wherein the adjusting the turn-off threshold light level sets the turn-off threshold light level to be: a fixed percentage above the representative current ambient light level; or a greater of light level of (i) the fixed percentage above the representative current ambient light level and (ii) a predefined minimum turn-off threshold light level.
7 . The electrical load controller of claim 2 , wherein the processing circuit is further configured to perform at the iteration, based on determining that the current ambient condition is nighttime: determining whether the representative current ambient light level has increased to a turn-off threshold light level.
8 . The electrical load controller of claim 7 , wherein the processing circuit is further configured to perform at the iteration, based on determining that the representative current ambient light level has increased to the turn-off threshold light level: setting the light/dark state to indicate the ambient condition as daytime; and controlling the switch to decouple the supply of electrical power from the lighting load; wherein based on controlling the switch to couple the supply of electrical power to the lighting load, the adjusting includes resetting the first timer.
9 . The electrical load controller of claim 2 , wherein the iteratively performing further includes, at an iteration of the multiple iterations: determining that (i) the first timer has lapsed, (ii) the current ambient condition is daytime and the representative current ambient light level has not decreased to a turn-on threshold light level, or (iii) the current ambient condition is nighttime and the representative current ambient light level has not increased to a turn-off threshold light level; and checking whether to adjust the turn-off threshold light level; wherein the adjusting includes incrementing or decrementing the first timer and incrementing or decrementing the second timer.
10 . The electrical load controller of claim 1 , wherein the iteratively performing is performed periodically at a sample frequency at which to sense a then-current ambient light level and determine an updated representative current ambient light level.
11 . The electrical load controller of claim 10 , wherein the iteratively performing is performed periodically using sleep and resume commands as part of a process to perform the multiple iterations.
12 . The electrical load controller of claim 1 , wherein, at each iteration of the multiple iterations, the determining the representative current ambient light level at the iteration includes determining the representative current ambient light level as a function of: the sensed current ambient light level at the iteration; and either (i) a plurality of previously-sensed current ambient light levels at a plurality of prior iterations of the multiple iterations or (ii) a plurality of previously-sensed current ambient light levels at a plurality of non-consecutive prior iterations of the multiple iterations, in which one or more previously-sensed current ambient light levels at other iterations of the multiple iterations are disregarded based on weather data indicating that low ambient light level readings are expected.
13 . The electrical load controller of claim 1 , wherein the electrical load controller is communicatively coupled to a plurality of ambient light sensors in the environment, and wherein the determining the representative current ambient light level includes averaging a plurality of sensed current ambient light levels sensed by the plurality of ambient light sensors in the environment.
14 . The electrical load controller of claim 1 , wherein the environment is an indoor environment, and wherein the processing circuit is further configured to control the switch to couple the supply of electrical power to the lighting load and decouple the supply of electrical power from the lighting load based on (i) an ambient light condition of an outdoor environment adjacent to the indoor environment, (ii) an ambient light condition of the indoor environment and factoring-out contribution of ambient light of the outdoor environment to a sensed ambient light in the indoor environment, or (iii) a combination of the ambient light condition of the indoor environment and the ambient light condition of the outdoor environment.
15 . A method for controlling conduction of a supply of electrical power to a lighting load in an environment, the method including: maintaining a light/dark state indicating a current ambient condition of the environment as being either daytime or nighttime; maintaining a first timer that dictates a minimum amount of time to lapse between consecutive transitions of a switch between coupling the supply of electrical power to the lighting load and decoupling the supply of electrical power from the lighting load; maintaining a second timer that dictates an amount of time to lapse, after controlling the switch of an electrical local controller to couple the supply of electrical power to the lighting load, before setting a turn-off threshold light level, the switch being controllable to selectively couple the supply of electrical power to the lighting load and decouple the supply of electrical power from the lighting load; and iteratively performing, over multiple iterations: determining a representative current ambient light level based at least in part on sensed current ambient light level sensed by one or more sensors; and adjusting the first timer and the second timer.
16 . The method of claim 15 , wherein the iteratively performing further includes determining whether the first timer has lapsed, and wherein the method further includes: based on determining at an iteration of the multiple iterations that the first timer has lapsed, that a current ambient condition as indicated by the light/dark state is daytime, and that the representative current ambient light level has decreased to a turn-on threshold light level: setting the light/dark state to indicate the ambient condition as nighttime; and controlling the switch to couple the supply of electrical power to the lighting load; wherein based on controlling the switch to couple the supply of electrical power to the lighting load, the adjusting includes resetting the first timer and the second timer; and performing, at a subsequent iteration of the multiple iterations, and based on the second timer lapsing, adjusting the turn-off threshold light level using the representative current ambient light level determined at the subsequent iteration, wherein the adjusting the turn-off threshold light level sets the turn-off threshold light level to be higher than the representative current ambient light level such that ambient light level in the environment must be brighter than the representative current ambient level for the processing circuit to control the switch to couple the supply of electrical power to the lighting load.
17 . The method of claim 15 , wherein the iteratively performing further includes determining whether the first timer has lapsed, and wherein the method further includes: based on determining at an iteration of the multiple iterations that the first timer has lapsed, that a current ambient condition as indicated by the light/dark state is nighttime, and that the representative current ambient light level has increased to a turn-off threshold light level: setting the light/dark state to indicate the ambient condition as daytime; and controlling the switch to decouple the supply of electrical power from the lighting load; wherein based on controlling the switch to couple the supply of electrical power to the lighting load, the adjusting includes resetting the first timer.
18 . The method of claim 15 , wherein the iteratively performing is performed periodically at a sample frequency at which to sense a then-current ambient light level and determine an updated representative current ambient light level.
19 . The method of claim 15 , wherein, at each iteration of the multiple iterations, the determining the representative current ambient light level at the iteration includes determining the representative current ambient light level as a function of: the sensed current ambient light level at the iteration; and either (i) a plurality of previously-sensed current ambient light levels at a plurality of prior iterations of the multiple iterations or (ii) a plurality of previously-sensed current ambient light levels at a plurality of non-consecutive prior iterations of the multiple iterations, in which one or more previously-sensed current ambient light levels at other iterations of the multiple iterations are disregarded based on weather data indicating that low ambient light level readings are expected.
20 . An electrical load controller for controlling conduction of a supply of electrical power to a lighting load in an environment, the electrical load controller including: a line input terminal and a load output terminal, the line input terminal configured to be electrically coupled to the supply of electrical power, and the load output terminal configured to be electrically coupled to the lighting load; a switch electrically coupled in series between the line input terminal and the load output terminal, the switch being controllable to selectively couple the supply of electrical power to the lighting load and decouple the supply of electrical power from the lighting load; and a processing circuit configured to iteratively perform, at each iteration of multiple iterations: determining a representative current ambient light level based at least in part on sensed current ambient light level sensed by one or more sensors; adjusting a first timer that dictates a minimum amount of time to lapse between consecutive transitions of the switch between coupling the supply of electrical power to the lighting load and decoupling the supply of electrical power from the lighting load; determining whether the first timer has lapsed; selecting first processing to perform based on whether the first timer has lapsed, the selected first processing being selected between (i) performing a switching determination based on the representative current ambient light level as to whether to control the switch to couple the supply of electrical power to the lighting load or decouple the supply of electrical power from the lighting load, and (ii) bypassing the switching determination; adjusting a second timer that dictates an amount of time to lapse, after controlling the switch to couple the supply of electrical power to the lighting load, before setting a turn-off threshold light level; and selecting second processing to perform based on whether the second timer has lapsed, the selected second processing being selected between (i) performing turn-off threshold light level processing that adjusts the turn-off threshold light level using the representative current ambient light level determined at the iteration to set the turn-off threshold light level to be higher than the representative current ambient light level such that ambient light level in the environment must be brighter than the representative current ambient level for the processing circuit to control the switch to couple the supply of electrical power to the lighting load, and (ii) bypassing the turn-off threshold light level processing.

Description

BACKGROUND Many electronic load controllers control the switching on and off of a load based on environmental conditions. In the example of a controller for an outdoor lighting load like a floodlight or landscape light, the controller might turn the light on and off in response to changes in ambient light level in the environment in which the light is situated. Often such controllers operate using a fixed light threshold, by which the lighting load is turned on when the ambient light in the environment is darker than the fixed light threshold, and is turned off when the ambient light in the environment is brighter than the fixed light threshold. Sometimes a fixed hysteresis is applied to the threshold such that the ambient light level in the environment must change by a certain amount above or below the fixed light threshold before the light state (on/off) is changed. SUMMARY The design or application of these controllers typically requires that an ambient light sensor be positioned such that the ambient light level being sensed/measured by the sensor is not significantly impacted by the light emitted from the light when it is switched on. Otherwise, switching on the light results in the ambient light sensor reading an artificially high ambient light level because the lighting load itself is contributing to the sensed level. This can cause the controller to switch off the lighting load as if the true ambient light level has risen above the threshold. Aspects described herein improve operation of ambient light sensor-based load control by adjusting a control threshold, for instance a turn-off threshold light level (also referred to herein as a “turn-off threshold”), based on the ambient light level as it is (or may be) affected by the controlled lighting load when switched on. In embodiments, after switching on the controlled lighting load and awaiting lapse of an amount of time thereafter, a process measures the then-current ambient light level and uses that measured, then-current ambient light level to determine and adjust/set a turn-off threshold light level. In some examples, the current ambient light level just sensed is, alone, taken as a good representation of the current ambient situation and is used as a “representative” current ambient light level based on which to set the turn-off threshold light level. In other examples, that current ambient light level is used in conjunction with one or more prior-sensed ambient light levels to form the ‘representative’ current ambient light level that is taken as the good representation of the current ambient situation and used to set the turn-off threshold light level. In either of these two situations, the current ambient light level is used in adjusting the turn-off threshold light level, which is the threshold used for determining whether to switch off the lighting load, i.e., cut the supply of electrical power to the lighting load. The turn-off threshold can be set such that ambient light level in the environment must be brighter than the representative current ambient light level (either the current ambient light level itself or another representative current ambient light level based thereon) by a certain amount before the light will be turned off. Without dynamically adjusting/setting the turn-off threshold in this manner, a situation of constant on/off cycling might result. If the ambient light sensor is impacted by the increased brightness caused by the controlled light turning on, the controller might turn back off the light soon after it turned on the load. This could cause the controller to turn back on the light and repeat this cycling on and off until true ambient light level is sufficiently high that it is above the turn-on threshold. Aspect can advantageously be applied in applications where an ambient light sensor is used to sense ambient light levels in an environment for use by a microcontroller or other processing circuit in determining when to switch on and off a lighting load in response to changes in the ambient light level. Examples of such applications are outdoor lighting controls that turn on lights when ambient light decreases sufficiently low (i.e., dark, nighttime) and subsequently turn off lights when ambient light increases sufficiently high (i.e., light, daytime). Shortcomings of the prior art are overcome and additional advantages are provided through the provision of an electrical load controller for controlling conduction of a supply of electrical power to a lighting load in an environment. The electrical load controller includes a line input terminal and a load output terminal, the line input terminal configured to be electrically coupled to the supply of electrical power, and the load output terminal configured to be electrically coupled to the lighting load. The electrical load controller also includes a sensor configured to sense ambient light levels in the environment, a switch electrically coupled in series between the