Receivers of pulsed infrared radiation. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Receivers of pulsed infrared radiation. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / infrared technology

Comments on the article

Of the photosensitive devices, not all have sufficient speed to respond to each flash of the IR diode. Typically, photodiodes are used in photodetectors of pulsed radiation (see Appendix 2)*.

Pulse microcurrents arising in the photodiode during its irradiation must be amplified and brought to the digital standard, i.e. convert each IR flash into a voltage pulse suitable for direct control of a digital microcircuit of one type or another.

The high input impedance and gain, the significant bandwidth of the amplifier, suitable for solving such a problem, make it sensitive to electrical pickups of various origins. Including the work of the electronic "stuffing" of the device, in which he enters himself. Therefore, the photodiode and its amplifier are usually carefully shielded.

The sensitivity of the photodetector can be noticeably reduced by parasitic illumination. Therefore, its photodiode is covered, as a rule, with a hood - a segment of a metal or plastic pipe blackened inside, fencing it off from light sources located away from the optical axis.

The direct, coaxial illumination of the photodiode is reduced by filters that attenuate the visible part of the illumination spectrum. It is better, of course, to use a special infrared filter for this with a transparency band that coincides with the emission spectrum of the IR diode. But experience shows that thin ebonite, getinax, colored polystyrene, dark plastic wallpaper can be a good IR filter. However, by almost completely "cutting off" visible light, such materials introduce a noticeable attenuation into the IR signal as well.

Although a modern photodiode, as a rule, has built-in optics concentrating the photoflux at its pn junction, its efficiency is relatively low due to its small size. The sensitivity of the photo head will increase significantly if its photodiode is placed at the focus of a lens with a diameter of 20...40 mm or more, concentrating a much larger light flux on it. In this capacity, you can use, for example, the condenser of a photo enlarger. Or a lens from an old camera with focusing "by meters", which will also allow you to fine-tune the optical channel in the best possible way.

*) Unsuitable, for example, photoresistors. Vacuum photocells and photomultipliers (PMTs) have sufficiently high speed. But for their power supply, high voltage sources are required: for photocells 50 ... 300 V, for photomultipliers - up to 1 kV and more (see Appendix 6). Considerable dimensions and fragility also limit the scope of their application.

Publication: cxem.net

See other articles Section infrared technology.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Alcohol content of warm beer 07.05.2024

Beer, as one of the most common alcoholic drinks, has its own unique taste, which can change depending on the temperature of consumption. A new study by an international team of scientists has found that beer temperature has a significant impact on the perception of alcoholic taste. The study, led by materials scientist Lei Jiang, found that at different temperatures, ethanol and water molecules form different types of clusters, which affects the perception of alcoholic taste. At low temperatures, more pyramid-like clusters form, which reduces the pungency of the "ethanol" taste and makes the drink taste less alcoholic. On the contrary, as the temperature increases, the clusters become more chain-like, resulting in a more pronounced alcoholic taste. This explains why the taste of some alcoholic drinks, such as baijiu, can change depending on temperature. The data obtained opens up new prospects for beverage manufacturers, ... >>

Major risk factor for gambling addiction 07.05.2024

Computer games are becoming an increasingly popular form of entertainment among teenagers, but the associated risk of gaming addiction remains a significant problem. American scientists conducted a study to determine the main factors contributing to this addiction and offer recommendations for its prevention. Over the course of six years, 385 teenagers were followed to find out what factors may predispose them to gambling addiction. The results showed that 90% of study participants were not at risk of addiction, while 10% became gambling addicts. It turned out that the key factor in the onset of gambling addiction is a low level of prosocial behavior. Teenagers with a low level of prosocial behavior do not show interest in the help and support of others, which can lead to a loss of contact with the real world and a deepening dependence on virtual reality offered by computer games. Based on these results, scientists ... >>

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Random news from the Archive

Series of ceramic diodes CeraDiode 23.01.2004

EPCOS launched the production of a series of ceramic diodes CeraDiode. The instruments are available in 0603 surface mount housings. They are about half the price of silicon diodes and are highly resistant to external electromagnetic influences.

Ceramic diodes operate with reverse voltages from 5,6 to 22 V, response time is 0,5 ns. A set of 1206 diodes is also available in the 4 package.

Other interesting news:

▪ With a load on my head

▪ Cheap ICs - Signal Generators

▪ Miniature proximity sensor based on vein pattern

▪ Fusion reactor five times brighter than the sun

▪ The influence of lunar cycles on human sleep

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Lecture notes, cheat sheets. Selection of articles

▪ article Man is a social animal. Popular expression

▪ article What are the signs of the onset of bad weather? Detailed answer

▪ article A mechanical assembly fitter, busy preparing the frames of the spring block and the mullion for the frame. Standard instruction on labor protection

▪ article Programmable code lock. Encyclopedia of radio electronics and electrical engineering

▪ article Broadband PA for television broadcasting. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews