Retrofit LED lamp assembly in a vending machine

Abstract

A retrofit LED lamp assembly and retrofitting method for use in a vending machine. The retrofit LED assembly having a plurality of light emitting diodes (LEDs) and a power connector adapted to connect to a source of power within a vending machine. A power regulating circuit adjustably controls the amount of power provided to the LEDs in response to control signals received by a communication circuit in the lamp assembly.

Claims

1. A lamp assembly designed to illuminate products in a vending machine, the lamp assembly comprising one or more light emitting diodes, and a control circuit connected to the one or more light emitting diodes and connectable to a source of power in the vending machine, the one or more light emitting diodes and the control circuit housed in a lamp housing having power connectors adapted to be mounted into a vending machine socket for a fluorescent lamp, the control circuit comprising a communications circuit for receiving control signals, the control circuit selectively controlling adjustment of the illumination provided by the one or more light emitting diodes based upon said control signals, wherein the control circuit communicates with a vending machine controller and receives the control signals from the vending machine controller.

2. The lamp assembly of claim 1 wherein the lamp assembly is employed as a retrofit replacement for a fluorescent lamp of a preexisting vending machine without having to re-wire an existing lighting system.

3. The lamp assembly of claim 1 wherein the lamp assembly is employed as a retrofit replacement for a fluorescent lamp of a preexisting vending machine without having to replace an existing fluorescent ballast.

4. The lamp assembly of claim 1 further comprising a wireless interface utilized in conjunction with a wireless remote control.

5. The lamp assembly of claim 1 wherein the vending machine socket is a standard fluorescent socket, and the lamp assembly further comprises pin terminals at each end compatible with mounting into the standard fluorescent socket.

6. The lamp assembly of claim 1 wherein the control circuit further comprises a current regulator circuit which eliminates variations between different fluorescent ballasts.

7. A method of retrofitting a fluorescent lamp mounted in a fluorescent lamp socket in a vending machine, the method comprising: removing the fluorescent lamp; and replacing the fluorescent lamp with a lamp assembly comprising one or more light emitting diodes, and a control circuit connected to the one or more light emitting diodes and to a source of power, the one or more light emitting diodes and the control circuit housed in a lamp housing having terminations adapted to be mounted in the fluorescent lamp socket, the control circuit comprising a communications circuit for receiving control signals, the control circuit selectively controlling adjustment of the illumination provided by the one or more light emitting diodes based upon said control signals; and providing the control signals by a vending machine controller.

8. The lamp assembly of claim 1 wherein the communication circuit further comprises a serial communication interface.

9. The lamp assembly of claim 1 wherein the communication circuit further comprises a vending industry standard interface.

10. The lamp assembly of claim 1 wherein the communication circuit further comprises an interface including both transmit and receive circuitry.

11. The lamp assembly of claim 1 wherein the communication circuit further comprises at least one of a serial interface, an optical interface or a wireless interface.

12. The lamp assembly of claim 1 wherein the communication circuit further comprises a connector and interface protocol implementing a vending industry standard.

13. The lamp assembly of claim 1 wherein the communication circuit implements an MDB interface.

14. A lamp assembly designed to illuminate products in a vending machine, the lamp assembly comprising one or more light emitting diodes, and a control circuit connected to the one or more light emitting diodes and connectable to a source of power in the vending machine, the one or more light emitting diodes and the control circuit housed in a lamp housing having power connectors adapted to be mounted into a vending machine socket for a fluorescent lamp, the control circuit comprising a communications circuit for receiving control signals, the control circuit selectively controlling adjustment of the illumination provided by the one or more light emitting diodes based upon said control signals; and power management circuitry to utilize an unregulated input voltage of 34 VDC supplied by the source of power in the vending machine, wherein the control circuit communicates with a vending machine controller and receives the control signals from the vending machine controller.

15. The lamp assembly of claim 14 wherein the power management circuitry is also compatible with a low voltage alternating current supply without any adjustments to the power management circuitry.

16. A lamp assembly designed to illuminate products in a vending machine, the lamp assembly comprising one or more light emitting diodes, and a control circuit connected to the one or more light emitting diodes and connectable to a source of power in the vending machine, the one or more light emitting diodes and the control circuit housed in a lamp housing having power connectors adapted to be mounted into a vending machine socket for a fluorescent lamp, the control circuit comprising a communications circuit for receiving control signals, the control circuit selectively controlling adjustment of the illumination provided by the one or more light emitting diodes based upon said control signals; and power management circuitry compatible with a 24 VAC supply, wherein the control circuit communicates with a vending machine controller and receives the control signals from the vending machine controller.

17. A lamp assembly designed to illuminate products in a vending machine, the lamp assembly comprising one or more light emitting diodes, and a control circuit connected to the one or more light emitting diodes and connectable to a source of power in the vending machine, the one or more light emitting diodes and the control circuit housed in a lamp housing having power connectors adapted to be mounted into a vending machine socket for a fluorescent lamp, the control circuit comprising a communications circuit for receiving control signals, the control circuit selectively controlling adjustment of the illumination provided by the one or more light emitting diodes based upon said control signals, wherein the control circuit communicates with a vending machine controller and receives the control signals from the vending machine controller, wherein the adjustment of the illumination comprises varying color temperature of white light produced by the lamp assembly to highlight colors of products illuminated in the vending machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 depicts a perspective view of a presently preferred embodiment of a LED based lamp suitable as a replacement fluorescent lamp in accordance with the present invention.

(2) FIG. 2 depicts an exploded view of a preferred configuration of the mounting pins to allow adjustability when mounting in existing lamp sockets.

(3) FIG. 3 depicts an arrangement of fixed length LED lamp strips suitable to be interconnected to create lamps of increased length.

(4) FIG. 4 depicts a block diagram of a standard fluorescent ballast and lamp wiring arrangement.

(5) FIG. 5 depicts a block diagram of the control circuit electronics associated with the LED based lamp to be used as a replacement for fluorescent lamps in accordance with the present invention.

(6) FIG. 6 depicts an electronics schematic for a preferred embodiment of the LED based lamp to be used as a replacement for fluorescent lamps in accordance with the present invention.

(7) FIGS. 7, 7-1, 7-2, 7-3, 7-4, 7-5, 7-6, 7-7 and 7-8 (collectively FIG. 7) depict an electronic schematic for a preferred embodiment of the LED based lamp with color control.

(8) FIG. 8 depicts a chart of typical color LED specifications.

(9) FIG. 9 depicts an LED lamp of the present invention with the vending industry standard MDB connectors.

(10) FIG. 10 depicts an alternate configuration of LEDs suitable for use in a fluorescent lamp replacement which has the ability to change colors.

(11) FIGS. 11A and 11B depict a vending machine utilizing the LED based lamp of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(12) Referring to FIG. 1, a perspective view, 100, of a presently preferred embodiment of the current invention is shown. An array of white LEDs, 102, are mounted to a printed circuit board, 103, that is then mounted to a metal extrusion, 104. A natural translucent white polystyrene lens, 106, is used to cover the LEDs and act as a diffusing lens. The assembly is terminated on both sides with pin terminals, 110, suitable to mount into standard fluorescent sockets. This allows standard fluorescent bulbs to be replaced by the LED lamp designed for this purpose and described in detail below. The terminals at the end of each of ends of the fluorescent lamp replacement assembly can be adjusted so the orientation of the lamp in the sockets is adjustable. This is best shown in FIG. 2. By positioning the end terminals 122a and 122b of the LED lamp, the light output from the lamp can be directed in any position in increments determined by the positioning wheel, 120a and 120b, from the standard mounting position. In a preferred embodiment of the fluorescent lamp mounting arrangement, the end terminals, 122a and 122b, are screw machined parts with threads, 123, which screw into the positioning wheels, 120a and 120b. The wires, 125,126 which are used to connect the end terminals, 122a and 122b, to the circuit board, 103, are terminated with ring terminals, 127 and 128, at one end and a connector, 129, at the other end. The connector, 129, will plug into its mate on the printed circuit board, 103. The terminal assembly is keyed to the mounting plates, 124a and 124b by pins shown in mounting plate 124b at 132 and then fastened by screws, 130 and 131. In a similar manner, other standard fluorescent lamp sizes and terminations can be emulated to allow the lamp of the current invention to be used as a replacement for most fluorescent lamp styles.

(13) An alternate assembly approach of the current invention is shown in FIG. 3. In this arrangement, individual strings of LEDs or arrays of LEDs are mounted on a single printed circuit board as shown. Groups of these circuit boards can be interconnected to allow larger lamps to be created from a group of LED arrays, 140, 141 and 142, such as the arrays of LEDs of FIG. 6, for example. Details related to the strings of LEDs and arrays of LEDs will be discussed below. These connectors are positioned so that a second LED assembly can be interconnected to the first making an assembly twice as long. Additional assemblies can be interconnected to provide increasing lengths of LED assemblies. This is particularly useful to allow replacement LED lamps to be designed with standard LED assemblies to produce 18, 24, 32 and other longer fluorescent bulb equivalents as well as in new design applications which are not bound by having to mount in standard fluorescent tube sockets, as in designing the LED lamp into equipment using a low voltage interface such as the MDB interface used in vending machines. This will be discussed in greater detail below.

(14) Referring to FIG. 4, a typical standard fluorescent ballast and fluorescent lamp block diagram is shown. Fluorescent lamps use a ballast to limit the voltage and current to the lamp once the lamp is on. Initially, the ballast provides filament current to start the lamp along with the use of a starter 206. The starter 206 effectively shorts the lamp until the filaments are powered and a supply of electrons is generated, at which time the starter 206 becomes an open circuit allowing the electrons to flow through the fluorescent tube. The electrons bombard the fluorescent material coating the lamp turning on the light. The details of operation of a fluorescent lamp are well understood and are only presented in summary foil for reference. Other ballast arrangements are also used and will not be discussed here as these are well known in the art. This typical arrangement is shown for illustrative purposes.

(15) Typically, an 18 watt fluorescent lamp 203 would use a fluorescent ballast 202 sourcing about 0.3 amps of current and having an inductance of approximately 0.5 Henries. This ballast limits the voltage to the fluorescent lamp to approximately 60 volts when the lamp is on as its reactance is approximately 200 ohms at 60 Hz. When the lamp is in the starting mode, the full line voltage of 120 volts 201 appears across the lamp, and, a starter device energizes the filaments at both ends of the lamp to ionize the gas within the lamp. As the filaments ignite the gases in the lamp, the rapid excitation of the gas causes the lamp to turn on while acting as negative impedance. The ballast now limits the voltage due to the inductive reactance of the ballast. An example of such a ballast is the Advance Transformer Company catalogue number LC-14-20C-20W.

(16) A preferred mode of the current invention is an LED based device that would be able to be fitted into a standard Fluorescent lamp socket. When using the LED lamp of the present invention, the starter 206 is removed from the fluorescent fixture. The LED fluorescent lamp replacement as shown in FIG. 5, in one embodiment would be mechanically compatible with a 24 tube such as the F18T8/CW/K24 fluorescent lamp. This control circuit consists in its simplest form, of an AC to DC Converter 301 or Bridge Rectifier, and a group of LEDs 303 connected in a series and/or parallel combination, depending upon the light output (power) desired. Further discussion on how these combinations are matched to the desired functionality of the replaced Fluorescent Lamp follows below. In order to have complete control over the light output of the LED replacement lamps, a current regulator circuit 302 can be added to the control circuit of the current invention to ensure the required current is determined by the lamp eliminating variations between ballasts. The current regulator circuit may be limited to a simple voltage limit to limit the maximum current drawn by the LED devices in the LED lamp. This will be discussed below in detail.

(17) A more detailed look at a preferred embodiment of the present invention is shown in FIG. 6. Referring to the lamp fixture 590, the existing fluorescent ballast 202 receives line voltage power 201 from a standard 120 VAC power source (US standards are used in this preferred embodiment). The output of the ballast 202 and 120 VAC power source 201 is supplied to the fluorescent lamp sockets 550 and 552. For the ballast type shown, a starter 206 is used as described above and is shown terminating at the second terminal pins at each fluorescent sockets 550 and 552. The present invention interfaces with the ballast 202 and power source 201 through the existing lamp sockets 550 and 552. The output of the ballast 202 and power source 201 is an AC signal as discussed above. FIG. 6 includes a schematic representation of two LED lamp assemblies, 140, 141 as earlier described in FIG. 3. A full wave diode bridge, 524 and 534 is used in each of these LED lamp assemblies to convert the AC signal to a DC signal to source the array of LEDs denoted by 520 a-p and 530 a-p for each of the two LED assemblies shown. The use of a full wave bridge for this application is well known in the art and is not explained further. A current balancing resistor 523 and 533 is in series with the diode bridges 524 and 534 respectively to balance the current to be supplied to each of the LED arrays. As seen, voltage limiter 522 and 532 limits the voltage to 60 volts using standard zener diodes as shown. The current supplied by the power source 201 and ballast 202 combination is determined by the ballast 202 which acts as a current limiting inductor of 0.5 Henry. At the line frequency of 60 Hz, the current capability of the ballast in the example of FIG. 6 is about 300 mA. Since this current supplies two LED arrays 140 and 141, each of these have about 150 mA of current available. The voltage limiters 522, 532 shown are 60 volt 5 watt zener diodes. These zener diodes assure the voltage across the array of LEDs does not exceed their voltage specifications. The typical voltage drop of white LEDs is 3.6V as shown in the chart in FIG. 8. The fifteen LEDs shown in each LED assembly 140 and 141 will therefore drop 153.6V or 54 Volts. The voltage source of the ballast 202 and power source 201 supply will be able to support this voltage as the inductor (ballast 202) will absorb the excess voltage available. The use of inductors and ballasts for current limiting is well known in the art and not further discussed here. The array of LEDs are shown in the preferred embodiment as two parallel combinations of 15 LEDs, 140 and 141, each parallel combination having current balancing resistors 523 and 533 to ensure the current through each of the parallel combinations of LEDs is approximately equal. Without these resistors, the current would divide based on the impedances differences of the arrays of LEDs which can be quite variable. The series combinations of LEDs are shown as 520a through 520p and 530a through 530p. Each of the LEDs in the preferred embodiment is watt rated and drop about 3.6 volts. The two parallel combinations of LEDs are shown drawing about 150 mA of current each.

(18) As described above in reference to FIG. 3, the LED arrays can be partitioned into individual assemblies to be interconnected to allow a family of products of varying lengths to be easily made. The two LED arrays of FIGS. 6, 140 and 141 each have their own diode bridge, 524 and 534, as well as their own voltage limiters 522 and 532, optional fuses, 525 and 535 as well as male and female connectors 526, 528, 536, 538 to allow for this interconnection. The lamp sockets, 129 in both are shown connected to a male connector, 546 in 560. This male connector 546 would interconnect to one of the female connectors 528 or 538 of the LED arrays. If the female connector 528 were used, the male connector from this LED array would be interconnected to the female connector 538 of the second LED array. The male connector 536 of this second LED array can then be interconnected to a third LED array, not shown, or to the socket 548 of assembly 580 which then interconnects to the other end lamp connector 129.

(19) The current invention provides an LED lamp which can be controlled in a number of ways including light intensity and color. The control circuit electronics can be embedded inside the lamp or provided externally through an interface unit, or even implemented in the controller system of the vending machine itself. FIG. 7 shows a preferred electronics schematic for controlling the multicolor LED lamp. Three arrays of color LEDs are used. To achieve full color capability it is well known in the art to use Red, Green and Blue to produce the color spectrum. In addition to production of colored light, various color temperatures of white light may be produced to highlight the colors of products illuminated in the vending machine.

(20) In this design, there are three constant current supplies 701, 721 and 741, one for each of the LED color arrays, namely Red 720, Green 730 and Blue 740 respectively. Each of these constant current supplies is independently controlled to allow the proper mix of each of the colors to produce any color required as described below. In order to allow the range of colors that may be desired from an LED RGB arrangement, some unique control techniques are required. The emitted wavelength from the chosen LED has to be known and consistent over the range of control required. As specified, the wavelength of a specific LED as determined by its manufacturer is at a specific current level. It is critical to ensure the specified current is used for each LED type chosen for each of the Red, Green and Blue LED arrays. The sample LED data sheet summary shown in FIG. 8 shows the characteristics and specifications of each of the Red, Green and Blue LED's used in the preferred embodiment. Additionally, the specifications for an Amber LED are shown. Amber and other colors can be used in addition to or in place of three colors used in the preferred embodiment. Each of these LED specifications indicate the wavelength specified is at a current of 140 mA. The constant current supplies 701, 721, and 741 will each be set for 140 mA per LED string to meet the manufacturer's specifications. An example LED string is shown in FIG. 7 for the Red array 720 as including LED 722, LED 724, and LED 726. Current balancing resistor 770 is also part of this LED string. Depending on the number of such strings controlled by the constant current supply 701, the total current required by the supply can be determined. The circuit shown in 701 is designed to supply up to 1 Amp of current, although the resistor ratio of resistor 707 and resistor 708 anticipates three LED strings with a required current up to 420 mA maximum.

(21) The current to each LED string and to each LED array will be fixed at this designed current so that when the switching supply 701 is conducting, independent of duty cycle, the current supplied is the specified current. This current is supplied to the source voltage on the LED array and is determined by the constant current supply 701 at output VREG RED. The duty cycle therefore determines what percent of the time this fixed current is supplied. The duty cycle is controlled by the Pulse Width Modulation Channel Controller 750 described below. Each of the three color LED analysis controlled similarly, optimized to ensure the fixed current used is per the manufacturer's specifications independent of the duty cycle.

(22) The details of the control of the current and duty cycle are further described. The constant current switch-mode supplies are similar for each of the three color LED arrays. The following description will be relative to the Red LED array 720 constant current switch-mode supply 701, but applies to each of the other two supplies as well. The constant current switch-mode supply is comprised of a Linear Technologies LT3474 device 702, inductor 703 and diode 704 configured as a conventional switching supply well known in the art and not described in detail here. This circuit is capable of supplying 12 watts of power to an array of LEDs. The device provides precise pulse by pulse current limiting, and also provides an input for PWM modulation. This input cuts off all current to the LED array during the PWM off time. So, when the LEDs are on, they receive their rated optimum operating current. In this design, each series leg of LEDs receives 140 milliamps of current when any current flows. The total current supplied by the constant current switch-mode supply is determined by the resistors 707 and 708.

(23) To control the intensity, a Microchip PIC16F737, 750 microcontroller with three PWM (Pulse Width Modulator) controllers is used. Each of the PWM controllers is delegated to a color, and, by changing the duty cycle of the PWM, the intensity of its corresponding color can be changed. PWM 751 controls the Red LED array 720, PWM 752 controls the Green LED array 730, and PWM 753 controls the Blue LED array 740.

(24) The wavelengths of the LEDs used in the preferred embodiment are shown in FIG. 8. By no means is this device limited to the above wavelengths. By using a longer wavelength blue, for instance 485 nanometers, a higher efficiency Lamp can be made. Amber is given as an alternate to Red, as it can also enhance the efficiency of the Lamp if the deep red color (which the eye is not very sensitive to) is not required, or desired.

(25) Small series resistance, nominally 5 ohms 770 through 778, is used to balance the current in each leg of LED's. This balancing resistor is needed so as to keep a leg of LED's with a low forward voltage from robbing all of the current of a series of LED's with a larger forward voltage. This eliminates having to select LED's with the same forward voltage drops to achieve the current balancing which would add to the cost of the LED's.

(26) The electronic circuit described can be embedded in the LED circuit assembly so that the LED lamp is an integrated smart product. Communications to the smart LED lamp can be through any number of generic or industry standard protocols. The LED replacement lamp of the current invention can be used as a replacement for a fluorescent lamp as described above, so long as the means to control the LED replacement lamp is provided. Alternatively, the lamp can be designed to work as a replacement for a fluorescent lamp and its ballast assembly by providing a power source directly to the lamp. This power source can be low voltage such as 24 VDC.

(27) The actual color that will be perceived will be determined by the ratio of light power output from each of the three color LED arrays. The light output of each of the LED arrays is also determined by the manufacture at the rated current. Therefore, the light output from each of the LED arrays can be controlled relative to the other LED arrays by controlling their respective PWM duty cycle. Either a formula or look up table can be used to define the duty cycle relationships between LED arrays to create any specific color output. The arrangement of the LED arrays along with the diffusing lens mixes the light outputs to ensure the desired color is produced. FIG. 10 shows a view of three LED array assemblies, 901, 902, and 903 with each assembly having a series of alternating Blue, 906, Green, 905, and Red, 904, LEDs. The configuration of the multicolor LEDs can be in any arrangement suitable to producing overlapping optical fields so they combine to form the desired colors. Alternatively, the LEDs can be multiplexed at high speed to provide the same optical effect although only one LED may be on at a time. This allows for multi die LEDs to be used as well.

(28) The vending industry, by way of example uses an MDB serial interface between peripherals and the vending machine controller. One embodiment of the current invention is a lamp tailored to the vending industry and intended to be controlled by a vending machine controller. The MDB master, or any appropriate serial communication device, can communicate with the Lamp PWM controller through this MDB interface, and change the intensity of each of the three colors, to produce color, change the intensity at a given color (or white) to achieve dimming, create special attention getting effects such as flashing or chasing lights, or control the power to the lamp to turn it off when not required.

(29) The vending industry standard interface, known as MDB is shown schematically in FIG. 7. The interface circuitry 800 provides both power from the MDB interface including an unregulated input voltage, typically 34 VDC, 801 and power return, 802. This power is used to power the LED lamp. The 34 VDC input relative to the power return is input to a voltage regulator 804 preferably an industry standard part such as the LM320 series regulator supplied by multiple sources. A full wave bridge, 304 is provided although not needed for this interface as the MDB input is already DC voltage. However, the inclusion of the full wave bridge allows low voltage AC to be used if insufficient power is available from the MDB source. A low voltage, 24 VAC supply could be used in place of the DC supply without any adjustments to the circuitry.

(30) The MDB interface includes both transmit, 830, and receive, 820, circuitry to isolate these signals from the source vending controller. Opto isolators 811 and 821 are shown for this purpose. The use of opto isolators for this purpose is fully understood in the art. Of course any suitable serial interface, optical interface, wireless interface, or the like can be used to communicate to the smart LED lamp.

(31) Referring to FIG. 9, LED lamp assembly, 800, is depicted with mounting brackets 801 and 802 to allow an alternate mounting arrangement to the standard fluorescent socket interface described above. Key hole, 803 and 804 mounting allows the LED lamp to be mounted in either a vertical or horizontal position. The length of the lamp can vary as discussed above using the inter-connecting LED boards. The electronic interface is adapted to the application with the vending standard MDB connector set 810 and 812 shown. This interface is described above. Clearly any type of connector and interface protocol can be used to adapt the current invention to specific industry applications.

(32) FIGS. 11A and B depict a vending machine 1100 (FIG. 11A) employing a vending controller 1150 (FIG. 11B) mounted inside the vending machine, but shown separately for ease of illustration, to control peripherals 1170, such as coin, bill, and card readers, also mounted internally, but shown externally for ease of illustration, utilizing a communication system 1160 implementing a communication interface, such as the MBD interface, or the like. As seen in FIG. 11B, the vending controller 1150 also communicates with and controls an LED based lamp 1180 in accordance with the present invention as addressed in detail above. Again, the LED based lamp 1180 is mounted internal to the vending machine 1100, but shown in the block diagram of FIG. 11B for ease of illustration. For example, lamp 1180 will typically be mounted above products to be vended by the vending machine 1100. As further seen in FIG. 11B, lamp 1180 has a DC power connector 1182 for connection to an existing source of available DC power 1190 within the vending machine 1100.

(33) While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than of limitation and that changes may be made within the purview of the appended claims without departing from the true scope and spirit of the invention in its broader aspects. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the spirit of the invention. The inventors further require that the scope accorded their claims be in accordance with the broadest possible construction available under the law as it exists on the date of filing hereof (and of the application from which this application obtains priority,) and that no narrowing of the scope of the appended claims be allowed due to subsequent changes in the law, as such a narrowing would constitute an ex post facto adjudication, and a taking without due process or just compensation.