Electric lamp and discharge devices: systems – Current and/or voltage regulation
Reexamination Certificate
1998-12-17
2003-03-04
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
C315S158000
Reexamination Certificate
active
06528954
ABSTRACT:
DESCRIPTION OF THE RELATED ART
Light emitting diodes are known which, when disposed on a circuit, accept electrical impulses from the circuit and convert the impulses into light signals. LEDs are energy efficient, they give off virtually no heat, and they have a long lifetime.
A number of types of LED exist, including air gap LEDs, GaAs light-emitting diodes (which may be doubled and packaged as single unit offer greater reliability than conventional single-diode package), polymer LEDs, and semi-conductor LEDs, among others. Most LEDs in current use are red. Conventional uses for LEDs include displays for low light environments, such as the flashing light on a modem or other computer component, or the digital display of a wrist watch. Improved LEDs have recently been used in arrays for longer lasting traffic lights. LEDs have been used in scoreboards and other displays. Also, LEDs have been placed in arrays and used as television displays. Although most LEDs in use are red, yellow or white, LEDs may take any color; moreover, a single LED may be designed to change colors to any color in the color spectrum in response to changing electrical signals.
It is well known that combining the projected light of one color with the projected light of another color will result in the creation of a third color. It is also well known that three commonly used primary colors—red, blue and green—can be combined in different proportions to generate almost any color in the visible spectrum. The present invention takes advantage of these effects by combining the projected light from at least two light emitting diodes (LEDS) of different primary colors. It should be understood that for purposes of this invention the term “primary colors” encompasses any different colors that can be combined to create other colors.
Computer lighting networks that use LEDs are also known. U.S. Pat. No. 5,420,482, issued to Phares, describes one such network that uses different colored LEDs to generate a selectable color, primarily for use in a display apparatus. U.S. Pat. No. 4,845,481, issued to Havel, is directed to a multicolored display device. Havel uses a pulse width modulated signal to provide current to respective LEDs at a particular duty cycle. U.S. Pat. No. 5,184,114, issued to Brown, shows an LED display system. U.S. Pat. No. 5,134,387, issued to Smith et al., is directed to an LED matrix display.
Illumination systems exist in which a network of individual lights is controlled by a central driver, which may be a computer-controlled driver. Such illumination systems include theatrical lighting systems. The USITT DMX-512 protocol was developed to deliver a stream of data from a theatrical console to a series of theatrical lights.
The DMX-512 protocol was originally designed to standardize the control of light dimmers by lighting consoles. The DMX-512 protocol is a multiplexed digital lighting control protocol with a signal to control 512 devices, such device including dimmers, scrollers, non-dim relays, parameters of a moving light, or a graphical light in a computerized virtual reality set. DMX-512 is used for control for a network of devices. The DMX-512 protocol employs digital signal codes. When a transmitting device, such as a lighting console, sends digital codes, a receiving device, such as a dimmer, transforms these codes into a function command, such as dimming to a specified level. With digital systems, signal integrity is compromised less over long cable runs, relative to analog control. When a coded string of
0
/
1
digits are sent and received, the device will perform the desired task.
In hardware terms, DMX-512 protocol information is transferred between devices over metal wires using the RS-485 hardware protocol. This involves the use of two wires, known as a twisted pair. The first wire is referred to as a data+wire, and the second wire is referred to as a data−wire. The voltage used on the line is typically positive five volts. By way of example, to transmit a logical one, the data+wire is taken to positive five volts, and the data−wire to zero volts. To transmit a logical zero, the data+wire goes to zero volts, and the data−wire to positive five volts. This is quite different from the more common RS-232 interface, where one wire is always kept at zero volts. In RS-232, a logical one is transmitted by putting between positive six and positive twelve volts on the line, and a logical zero is transmitted by putting a voltage between negative six and negative twelve volts onto the line. RS-485 is generally understood to be better for data transmission than RS-232. With RS-232, the receiver has to measure if the incoming voltage is positive or negative. With RS-485, the receiver only needs to determine which line has the higher voltage on it.
The two wires over which RS-485 is transmitted are preferably twisted. Twisting means that disturbances on the line tend to affect both lines simultaneously, more or less by the same amount, so that the voltage on both lines will fluctuate, but the difference in voltage between the lines remains the same. The result is that noise is rejected from the line. Also, the drive capability of RS-485 drivers is higher than RS-232 drivers. As a result, the RS-485 protocol can connect devices over distances hundreds of times further than would be possible when using RS-232. RS-485 also increases the maximum data rate, i.e., the maximum amount of data which can be transmitted over the line every second. Communication between devices using RS-232 is normally about nine thousand six hundred baud (bits per second). Faster communication is possible, but the distances over which data can be transmitted are reduced significantly if communication is faster. By comparison, DMX-512 (using RS-485) permits data to be sent at two hundred fifty thousand baud (two hundred fifty thousand bits per second) over distances of hundreds of meters without problems. Every byte transmitted has one start bit, which is used to warn the receiver that the next character is starting, eight data bits (this conveys up to two hundred fifty six different levels) and two stop bits, which are used to tell the receiver that this is the end of the character. This means that every byte is transmitted as eleven bits, so that the length of each character is forty-four micro seconds.
The receiver looks at the two incoming signals on a pair of pins and compares the differences. A voltage rise on one wire and the inverse on the other will be seen as a differential and therefore deciphered as a digit. When both signals are identical, no difference is recognized and no digit deciphered. If interference was accidently transmitted along the line, it would impart no response as long as the interference was identical on both lines. The proximity of the two lines assist in assuring that distribution of interference is identical on both wires. The signal driver sends five hundred twelve device codes in a continual, repetitive stream of data. The receiving device is addressed with a number between one and five hundred twelve so it will respond only to data that corresponds to its assigned address.
A terminator resistor is typically installed at the end of a DMX line of devices, which reduces the possibility of signal reflection which can create errors in the DMX signal. The ohm value of the resistor is determined by the cable type used. Some devices allow for self termination at the end of the line. Multiple lines of DMX data can be distributed through an opto-repeater. This device creates a physical break in the line by transforming the electrical signals into light which spans a gap, then it is restored to electrical signals. This protects devices from damaging high voltage, accidentally travelling along the network. It will also repeat the original DMX data to several output lines. The input data is recreated at the outputs, eliminating distortion. The signal leaves the opto-repeater as strong as it left the console.
DMX messages are typically generated through computer software. E
Lys Ihor
Mueller George G.
Color Kinetics Incorporated
Vu David
Wolf Greenfield & Sacks PC
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