Title of Invention

A DEVICE FOR AUTOMATIC AND/OR DIMMING OF LAMPS AT A PRE-DETERMINED AMBIENT LIGHT

Abstract

A device for automatic switching and/or dimming of lamps at a predetermined ambient light. It comprises of an infra-red light sensor with a pre-determined field of view, to provide input signals to an amplifier depending upon the level of illumination exposed to the said infrared sensor. The amplifier output is connected through an analog to digital converter to obtain digital output corresponding to the signal from the said infrared sensor. The digital output is connected to a signal processor having a programmable memory, an oscillator to generate timing pulses to the said processor, receiving means to receive required manually controlled, selectable inputs to said processor, an actuator drive to actuate actuators connected to the lamps for switching on and off or dimming of the said lamps.

Full Text

The invention relates to a device for automatic switching and/or dimming of lamps at a pre-determined ambient light. Outdoors places like roads, yards, campuses, gardens, public places, private yards, offices, factories and all such places where human vision needs to be aided artificially are provided with luminaries working on electrical energy. The illuminance level required at the targeted area also varies depending on the purpose and timing. These luminaries are controlled through switches, which are manually operated for making of breaking the electrical circuit. The requirement of the duration for which these luminaries are to function each day depend on the user's requirements. For example, streetlights are switches ON at dusk and are switched OFF generally by dawn. Lights intended to illuminate advertisement boards are switched ON at dusk and switched OFF some time late in the night itself instead of waiting till dawn. Similarly a few luminaries can be operated at different wattage at different times depending on the need. For example general road lighting level can be reduced in the late night when the traffic density reduces which leads to saving in the energy consumption for illumination purposes. The manual operation of the switches at the appropriate time needs dedicated human attention and this involves costs and is prone to errors leading to energy wastage and sometimes non-provision of the required illumination when it is needed. Similarly changing the wattage rating of the luminaries involves altering the switching route which is to be operated manually is prone to errors and delays. The basis purpose of the invention is to provide a substitute for manual switching of luminaries based on natural light levels, Additional capabilities of switching off based on duration elapsed from dusk is contemplated to further help the user in saving energy. Additional capability of changing the wattage of the lamp is provided to further help the user to realise the goal of energy saving. The invention provides various options to offer flexibility to the user. A device based on mere visible light as input for automatic operation may not serve the total requirement as some times fights need to be switched OFF during night time itself at a particular physical time. The other limitation of visible light sensor based automation is that the sensor may mistake the lamp's output it is controlling as natural light. Similarly a device based on pure real time also may not serve the purpose totally as the solar radiation levels vary in terms of time depending on seasons in the year. Weather conditions will also have a bearing on the visibility levels on a particular day irrespective of the time. A device with a capability of taking both natural light and time expressed as duration elapsed from dusk instead of real time as inputs and performing based on integration of both will serve the purpose better. This duration based time concept also eliminates the need to set and/or correct the real time clock by the user, which means simplicity in operation. The construction technique of the device is such that the light sensor part will be unaffected by bird droppings, dust settlements, etc. The construction technique also provides accessible flexible choice of settings to the user to opt for switching OFF based on dawn or time elapsed from dusk. The selection procedure also facilitates the user to select the duration for each of the wattage of the luminary that is controlled by the invention. Hence the object of the present invention is to provide a device for automatically operating the circuit of luminaries both outdoors and indoors with flexible operational features to meet the field requirements of a variety of users of luminaries. The device according to this invention is provided with atleast one light sensor, which may be a PIN silicon photo diode, or any other opto sensor. A main's transformer will isolate the input and provide the reduced voltage to the circuit. A surge suppressor provides the needed protection against high voltage. A bridge rectifier rectifies the AC into DC. A voltage regulator is employed to control the input voltage to the circuit. The light sensor is connected to current -to-voltage converter and to at least one amplifier that amplifies the signals further. A comparator with built-in hysterisis is used to convert the analog light signal into a digital output form. The comparator will have the flexibility to select the transitional light levels to recognize the dusk and dawn levels in regular production. An oscillator of known frequency enables the microprocessor to keep track of physical time expressed in common units of hour or part there of, elapsed from the sensing of dusk. A Switch is provided to enable the user to select the duration elapsed after dusk at which the device shall switch OFF the load lamps or alternatively to change the wattage levels. Option is also provided for the user to select switching OFF of the lamps at dawn based on ambient light level irrespective of the time. The needed logic is built into the micro controller to process all the inputs like light level, time elapsed, mains' power status, user selection, etc. to drive the final actuator as per the selection exercised by the user. The user selection is fed and read by the microcontroller. The resolution of the light and time processing capability of the microcontroller will be tuned as per user requirements to provide the needed calibration and tolerance. An actuator is used to switch ON and switch OFF the luminaries to be controlled by the device. Additional actuator will be employed to change the wattage selection. The actuator is a relay and relay driver. The relay could be an Electro-mechanical or solid state type. Electro-mechanical type will be economical while the solid-state type will endure better. Signal received from the micro controller enables the actuator to switch ON and switch OFF the load or to change the wattage tapings. The device will be connected to the LT mains supply operating at 230V AC 50 Hz or at 110V AC and will automatically control the switching circuit(s) of luminaries meant for operation on the selected mains voltage. The control and drive circuits as distinct from the actuator will use the regulated DC derived from the 230V AC internally by the device. A back-up rechargeable battery will provide the needed power supply during mains power failure to enable continued processing of both light and time inputs so as to maintain the integrity and reliability of the judgement of the device. The optosensor according to this invention may be near infrared sensor with spectral response in the IR range of 800nm to 1100nm to ensure that the sensor will be highly immune to low pressure mercury, high pressure mercury and high pressure sodium vapor lamps. The field of view of the sensor is also restricted and aimed at the desired direction so that it does not receive the light emitted by sources located below its height, when installed in the field. The electronic and processing circuit of the device is housed in a contained in such a way that, when installed in outdoors as per the procedure, the rainwater will drop down and does not enter into the circuit area of the device. Visual indications can be provided as an option to indicate the functional state of the device. Accordingly the present invention provides a device for automatic switching and/or dimming of lamps at a pre-determined ambient light comprising an infra-red light sensor with a pre-determined field of view to provide input signals to an amplifier depending upon the level of illumination exposed to the said infrared sensor, the said amplifier output being connected through an analog to digital converter to obtain digital output corresponding to the signal from the said infrared sensor, characterised in that the said digital output is connected to a signal processor having a programmable memory; an oscillator to generate timing pulses to the said processor; receiving means to receive required manually controlled, selectable inputs to said processor; an actuator drive to actuate actuators connected to the lamps for switching on and off or dining of t\ip $aid lamps and the said signal processor is provided with a rechargeable secondary battery to ensure that the processing of the processor is immune to mains power interruptions. The device according to the invention will now be described with reference to the accompanying drawings wherein: Figure 1 shows the block diagram Figure 2 shows the voltage control system Figure 3 shows the opto sensing system Figure 4 shows the timing and logic system and the display system Figure 5 shows the actuator drive and actuator system Figure 6 shows the manual control system ,i a., Referring to Figure - 1: The block diagram indicates the outline of the device wherein the voltage control system provides the needed regulated rectifier DC to the other systems. The opto-sensing system senses the ambient light and supplies the logic system with the converted and amplified electrical signal in analogue form. The timing and logic system keeps physical time record and processes the signals of opto sensing system and he manual control system. The same system controls the actuator drive system and the display system. The actuator handles the load of the luminaries anr* trmVpc nr hr^Vc th** ^wtnV r\r™\t nf th** luminaries controlled by the device. Referring to Figure -2 It shows the voltage control system. The transformer is to isolate the mains supply and to provide the stepped down AC voltage. The varistor is to protect the transformer from spikes and surges. The full wave bridge rectifier is to provide DC. The capacitor is to minimize the ripples and the zenor diode is to regulate the level of DC voltage. The rechargeable secondary battery is to ensure the necessary back up in the event of power failure. R2 limits the charge current of the battery. 'A' is connected to the logic system to monitor the presence or absence of the mains voltage and to enable the memory regarding mains power interruptions. This capability is to ensure that the user's intention of maintaining the lamp output for a particular duration from dusk is realized irrespective of the mains power interruptions on any day. 'B' powers the logic system. 'C is fed to the coil of the relay. Referring to Figure - 3 !t shows the Optosensing circuit. OS1 is a PIN silicon photodiode with spectral response in the near IR zone. This spectral response ensures that the sensing element is immune to light emitted by normal artificial light sources like low pressure mercury vapor lamps, high pressure mercury vapor lamps and high pressure sodium vapor lamps. As the solar radiation consists of emissions in the near IR zone the device will still be able to recognize the level of ambient solar radiation levels and so can judge the day/night situation. Ua is the basic photocurrent to voltage converter. R1 and R2 are to enable the fixation of photo current conversion ratio. Ub is an amplifier with an amplification ratio of 1 + (R7/R6). Uc is a non inverting amplifier with zero gain to ensure that the reference of the non inverting input of Ua is not referenced to the ground but at an elevated level of say 200 Millie volts. The output of Ua will be in direct proportion to the incident light and the same is amplified in proportion of 1+R7/R6 of Ub. The photosensitive area and the light conversion efficiency of the OS1 coupled with the window size and the field of view will take into account the calibration parameters of the light sensing circuit. The amplified output of Ub represented as 'C will be fed to the logic processor for further processing as per the set program. 'A' provides the positive voltage and 'B' refers to the circuit ground. Referring to Figure - 4 It shows micro controller based logic system. Any general microcontroller with analogue and digital input processing capability can be used. The timing pulse generator can be a part of the processor system or outside. Analogue inputs are fed from 'C of figure 3 and 'A' of figure 6. Digital input is fed from 'A' of figure 2. The processor system will be equipped with the needed program memory and will continue the process irrespective of the presence or otherwise of the mains power. The processor maintains the record of the ambient light levels and the time elapsed from dusk and will maintain the output in accordance with the user selection. The user selection is read by the processor and implemented in accordance with the software program. The processor system controls the actuator drive system and display system. As an example one can use the microcontroller PIC16LC711, which is capable of processing both analogue and digital, and is capable of maintaining it's own clock frequency and can drive digital controls. The logic system also contains delay programs such that short duration variations in the ambient light conditions due to unnatural will not lead to misjudgment. Referring to Figure - 5 It shows a relay (actuator) drive circuit consisting of a resistor, an NPN transistor etc. and the actuator system. 'A' and 'D' represents the drive signals from the processor system. 'B' represents the AC input to the contact of the actuator. The NPN transistors' T1 and 12, when in conduction, will energize the coils of the respective relay system. 'C feeds the coil with the needed voltage level connected to 'C in figure-2. The transistor drive is derived from the logic processor system. The relay system consists of a one normally open contact based Electro mechanical relay which when energized will close the AC circuit of the luminaries intended to be controlled by the device. The above output can be fed to another relay system with one changeover type contact to facilitate the operation of the specific switch circuit in case the wattage selection is also desired. 'E' and 'F' represent the two outputs. The impedance levels to match the wattage can be set outside the device as per field and user requirements. Referring to Figure - 6 It shows the user selection switch system using a one pole 12 way rotary switch and each of the position refers to different selection by the user with regard to the duration for which the load has to be operated by the device. SW1 represents a single pole 12 position rotary switch. 'A' represents the input to the resistor divider network. R1 to R12 divide the voltage and the output level represented by 'B' at any point depends on the position of the switch. These analogue levels can be read and interpreted by the logic processor and controls the output as per user selection. The definition of the settings can be varied as per requirements. One example will be to offer the user a facility to choose the duration for which the device has to keep the lamps on after dusk each day. One of the 12 positions may as an example provide for dawn based switch OFF of the lamps which is appropriate for control of lighting in public places like street, roads etc. Similarly, as an example, 2 of the above 12 positions can be used to enable the user to opt for override purpose of the automatic function of the device to attend to repairs of the circuit which is being controlled by the device. The override may help the user to maintain a dead current zone or to provide a closed circuit for study of a live situation. The description along with the drawings shown here is only illustrative and is only one of the known methods of realizing the invention. This description will not limit the construction methods of the invention or any of the sub-systems or systems. WE CLAIM : 1. A device for automatic switching and/or dimming of lamps at a predetermined ambient light comprising an infra-red light sensor with a predetermined field of view to provide input signals to an amplifier depending upon the level of illumination exposed to the said infrared sensor, the said amplifier output being connected through an analog to digital converter to obtain digital output corresponding to the signal from the said infrared sensor, characterised in that the said digital output is connected to a signal processor having a programmable memory; an oscillator to generate timing pulses to the said processor; receiving means to receive required manually controlled, selectable inputs to said processor; an actuator drive to actuate actuators connected to the lamps for switching on and off or dimming of the said lamps and the said signal processor is provided with a rechargeable secondary battery to ensure that the processing of the processor is immune to mains power interruptions. 2. The device as claimed in claim 1, wherein the said infra-red sensor has a spectral response in the near infra-red zone to ensure insensitivity to the light in the visible spectrum. 3. A device for automatic switching and/or dimming of lamps at a predetermined ambient light, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

2487-mas-1998 abstract-granded.pdf

2487-mas-1998 claims-granded.pdf

2487-mas-1998 description (complete)-granded.pdf

2487-mas-1998 drawings-granded.pdf

2487-mas-1998-abstract.pdf

2487-mas-1998-assignment.pdf

2487-mas-1998-claims.pdf

2487-mas-1998-correspondence others.pdf

2487-mas-1998-correspondence po.pdf

2487-mas-1998-description complete.pdf

2487-mas-1998-drawings.pdf

2487-mas-1998-form 1.pdf

2487-mas-1998-form 26.pdf

2487-mas-1998-form 3.pdf

2487-mas-1998-form 6.pdf