日期：2012年8月6日

shop led lights and led drivers

We developed an array of signal processing systems (led lights), due to the array antenna must be placed in the surrounding open area, and array signal processing unit is located in a circular array antenna central location, which requires a computer outside of the array signal processing unit in 1 ~ 2km between the duplex communication. Proportion in the time index in the entire system in order to reduce the data transmission time, the data transfer rate should be not less than the rate of E1 (2.048Mb / s), and ask the communications link is safe, reliable. Analysis of various data communication technologies, the final choice of a fiber-optic key road, and achieved satisfactory results.

A copper media data link

Also requires a higher data transmission rates and longer communication distance in the copper media link coding and modulation is difficult to meet the index requirements, but the high-speed modem is not only expensive, but the handshake process time-consuming random real-time requirements field of the transmission data will obviously not apply. The most important thing is that the traditional copper media link produces both electromagnetic interference signals, and also easily affected by electromagnetic interference, and difficult to meet the requirements of the EMC (electromagnetic compatibility) and EMI (electromagnetic interference) standards.

Analysis of two fiber-optic link

The traditional image of the people, the fiber used in short-distance communication is not economical, but it has a copper media key road incomparable advantages: ① fiber link is neither emit electromagnetic wave, is not affected, there is no interference between the fiber error rate is greatly reduced. The designers do not consider the incoming ambient noise may be coupled; ② fiber to provide a communication link between the two electrically isolated to eliminate the problems caused by ground potential between the long-distance equipment. Designers no longer have to impedance matching and a headache; ③ fiber-optic transmitter can be digital modulation driving circuit. Digital baseband signal through a simple line coding, you can directly drive the fiber optic transmitter.

Now, the price of fiber optic devices than ever before has been a sharp decline, With the cable price increases and the fiber-optic device prices to decline further in the future, when people choose fiber is no longer first consider the price factor. Therefore, considering the speed and distance indicators, select the appropriate type of fiber transceiver and its drive circuit, high performance and low cost fiber-optic communication key road, this is the focus of this paper to.

The choice of optical fiber communication devices

A basic fiber-optic communication system is very simple: an LED panel emitter electrical signals into optical signals, and the coupling into the transmission fiber, the optical signal through the fiber to reach the optical receiver, the received optical signal back into the original the electrical signal output.
· Cable options: general, quartz glass fiber due to its low loss, high bandwidth for long-distance communications links, such as Ethernet and FDDI standard specifies multimode 62.5/125μm quartz glass fiber. Thin core fiber requires high-precision connectors to reduce the coupling loss, low-cost cables and connectors for industrial applications. 1mm POF (Plymer Optical Fibers) and 200μm HCS (Hard Clad Silica) fiber is the best choice, they are the step-index multimode fiber.
1mm POF typical loss value at 650nm wavelength is 0.2dB / m, 200μm HCS fiber to only 8dB/km 650mm wavelength typical loss value, less in the 820nm wavelength. HCS fiber is the core of the quartz glass cladding is a patented high-strength polymers, not only increased the intensity of the optical fiber, and moisture, pollution prevention and the outer sheath of PVC 2.2mm. HCS fiber can work in a 40 ℃ ~ +85 ℃ temperature range, the erection of a temperature range of 20 ℃ to +85 ° C, in both performance and price to meet the system requirements.
· Operating wavelength choice: fiber optic communication system design must take into account the impact of fiber loss and dispersion of the system, due to loss and dispersion are related to the operating wavelength of the system, the operating wavelength choose to become a major problem in system design. Consider the system specifications and selected fiber, select the 820nm wavelength enables HCS fiber loss as low as 6dB/km dispersion has reached the minimum.
· Choice of light source: LED can be selected in the 820m wavelength light compared with the semiconductor laser, the LED drive circuit is simple and low cost.

shop led lights and led drivers
In summary, the cable selection 200μm HCS fiber optical transceiver device selection of the 820nm wavelength of the HP’s HFBR-0400 series. In the 1500m distance in the series HFBR-14X2/HFBR- 24X2 reach 5MBd rate of the operating temperature range from 40 ℃ to +85 ° C, ST, SMA, SC and FC, multiple port models to choose from. HFBR-14XZ type AlGaAs LED tubes with 820nm wavelength HFBR-24XZ internal integration of an IC chip including PIN photo detector, the DC amplifier, and the open collector output Schottky transistor, its output directly with popular TTL and CMOS IC connected.

4 A practical fiber optic LED driver circuit

The fiber optic duplex communication system in which the role of the driver circuit is to convert electrical power into optical power, and modulation of the transmission of electrical signals to the output of the light source, its light while providing the bias current and changes with the digital signal modulation current.

Design LED driver circuit must first consider the peak of the LED drive current, and if more than the peak drive current produced by the optical signal will overshoot phenomenon. Chong, resulting in the receiving device to cause the signal coupled from the amplifier noise, the results may be beyond the detection threshold of the comparator, causing the error. LED has extinguished than the features lit difficulties, it will produce a smearing, This phenomenon is particularly evident when using the serial driver circuit. The parallel drive mode can provide a low resistance channel for the carrier in the LED, thereby reducing the pulse width distortion and slow smearing.

Resistance RSI in the drive circuit is used to adjust the optical output power, be careful not to exceed the peak drive current of the LED, or optical signal will overshoot. Another circuit of the SN75451 with the characteristics of low impedance, high current rate, to avoid the long tail phenomenon.

Pulse width distortion (PWD) is a major factor to limit the rate of fiber-optic link, which is caused by transmission delay between the input and output are not equal. Noted that PWD is always positive, so we can take advantage of the RC circuit to delay the LED is lit.

The optical receiver circuit is an important part of the optical fiber communication system, its performance is good or bad is a comprehensive reflection of the optical fiber communication system performance. Its role is to optical fiber transmission over optical signals into electrical signals, then amplified and balanced, the decision circuit and restore the original signal of the transmitter.

The presence or absence of the commonly used optical signal in optical fiber transmission line, “1” and “0” code in order to avoid the long stream even “0” or long even “one”, conducive to the extraction of the clock, the need for coding circuit. Array signal processor is sent to the parallel data rate and conversion circuits.

Comparisons between conventional tunnel lighting technology and LED tunnel lighting technology

Currently, tunnel lighting still utilized high pressure sodium lamps as lighting sources. But in recent researches, scientists found that high pressure sodium lamps has a relatively high radiation value, which was far exceeds the safety indicator and caused potential damages to human bodies. Besides high pressure sodium lamps have defects in CRI, the visual sensitivity characteristic, power specifications and brightness control. The new developed LED tunnel lighting technology overcame all sorts of disadvantages brought by high pressure sodium tunnel lamps and became the mainstream in tunnel lighting area.

 

Comparisons between conventional tunnel lighting technology and LED tunnel lighting technology

 

Light Emitting Diode is a new lighting technology based on semiconductor technique. In the early stage, LED can only emit red rays, which were mainly used as indicators in electrical appliances. With the development of LED technology, LED can send out multiple color rays. Nowadays, LED technology has been commonly used in many industries, such like display, single lighting, backlighting, street lighting, tunnel lighting, vehicle lighting, outdoor landscape lighting and indoor lighting. The biggest advantage of LED tunnel lighting technology is light dimmable. Many LED manufactures started to think over embedding calculation components within their LED tunneling lighting products to make them more intelligent and more human-based.

 

Properties of LED tunnel lighting technology:

1)       Consume less power. Compared with traditional high pressure sodium lamps, LED tunnel lights can save more than 40% energy.

2)       High longer service life. In ideal conditions, LED tunnel lights can continuously work for 100,000 hours.

3)       Higher reliability. Costs of daily maintenance and repair are quite low. The average normal working (without any faults) time can reach up to 20,000 hours, while high pressure sodium lights can maintain a constant normal working for less than 10,000 hours.

4)       Reduce the costs of power distribution system (cables, transformers, distribution boxes, bridges, etc.). In cases of long distance projects, the costs of power distribution system occupied a large ratio. Applying LED lighting technology can dramatically reduce the costs.

5)       LED tunnel lights can realize “instant-on”, easy for brightness adjustment, with no flickers, with wide start voltage range, embedded with multiple energy-saving modes (like intelligently adjust brightness according to the number of cars within tunnels).

6)       LED tunnels lights are free of toxic chemical pollution substances, such like mercury, lead and other health-hazard materials.

LED area light source technology found breakthrough in Nanjing

LED lighting technology is more advanced than traditional lighting in energy consuming, environmental protection and health-hazard aspects. The current used lighting source for LED lights is so called “spot lighting source”, which has some defects: inevitable lighting attenuation, higher costs and poor performance of cooling sections. These defects exerted a bad effect on their promotion process. With the becoming mature of LED chip technology, “area light sources” are no longer a myth. Then designers and LED engineers started to realize that replacing spot light sources by LED area light source technology is a key point to overcoming the defects of the existing LED lighting products. Under the support of the “Nanjing 321 plan” issued by Nanjing Government in last month, LED area light source technology found breakthrough in Nanjing.

 

LED area light source technology found breakthrough in Nanjing

 

In the Science and Innovation Park of Nanjing University of Technology reporters found this “area light source”. Nanjing XiongYan Optoelectronics Technology Co., Ltd. demonstrated a recently developed table lamps used LED area light source technology. Only judging from the space, this table lamp has nothing special, just like an ordinary table light. However, it is amazed that this LED table light has no bulbs but still can emit soft yellow white rays.

 

“All light are coming from this small light-emitting sheet.” Introduced by Mr. Guohua Bian, general manager of Nanjing XiongYan Optoelectronics Technology Co., Ltd.. On his palm we found a tiny circular sheet (with a diameter around 4cm, with a wideness about 1mm, and covered with yellow phosphor powder and small black spots), which is rather unnoticeable. “Each black spot is a lighting source. All these 3000 thousand small lighting sources have been evenly arranged on this sheet. We called it are light source. Every sheet consumes a power of 3W, but can replace a 20W traditional table lights. This table light has been installed 10 pieces lighting sheets just like this one, which means this lamps are equivalent to a 100W filament table lights. ”

 

In Mr. Bian’s words, his company spent totally 30 million yuan on developing LED area light source technology. It is a light source technology that more advanced than spot light source, less light attenuation, more easily-be-realized cooling design.

Analysis for LED explosion proof lighting technology

LED explosion proof lighting technology is typically led lights used in places which have relatively high risks in explosion, such like chemical plants, mines and gas stations. These places are full filled with explosive mixtures: explosive gas atmospheres, explosive dust environment and methane gas. Specific measurements should be taken before installing corresponding explosion-proof lamps. One of the most important working principles of LED explosive lights is restrict the contact surface of covers/shells with explosive gases or dusts and meanwhile keep the surface temperature of lamp compartments and electronic components under a safe level. Normally, this safe level is set as the minimum ignition temperature of the surrounding explosive gases. That the reason why measurements and tests should be conducted before installing these lamps. Only in the condition of knowing the major constitutions of the gas mixtures that suitable LED explosion proof lamps can be chosen.

 

LED explosion proof lighting technology is typically used in places which have relatively high risks in explosion, such like chemical plants, mines and gas stations.

 

LED is classified as a type cold solid lighting source, with high eletro-optical conversion efficiency, lower level of heat generation and longer service life. Thus high-power White-ray LED Explosion Proof Lamps are ideal lighting applications. Once promoted, LED explosion proof lighting technology gain a rapid development in this area.

 

LED explosion proof lights are mainly composed of lamp shells, lamp covers mounted in front of metal shells, internal lighting sources and batteries, switches and other compartments. Their major properties:

 

Lighting sources are made up of high-power LED modules. Wide input voltage drives (include constant-current chips, power supplier module) are set between lighting sources and batteries. In most cases, power supplier modules are connected directly with constant-current chips and plastically sealed together with LED modules.

 

The low heat generation of LED lighting sources helped to realize the internal temperature control property to some degrees. Both in battery-fully-charged phases and in battery-nearly-worn-out phases, LED lighting sources can maintain a constant brightness. Low-power LED explosion-proof lights are usually made as portable. It is a recently-developed technology according to the demand of the market. Heat sinks are set on the surface of shells (within lamp covers), which can effectively conduction unwanted heat created during the operation. LED explosive-proof lamps are more reliable than other LED lighting products and were used in a variety of industries, such as coal, petroleum, railway, etc.