LEDs are long and are widely used in various devices. Nevertheless, this time now open their new capabilities that allow the use of LEDs in several "non-traditional" modes and schemes.
Depending on the type of led light crystals Dov (LED) light emitted in the visible or infra red part of the spectrum. If radiation is carried out in the visible part of the spectrum of the human eye, it is perceived by humans as glow a certain color LED. For example, domestic agricultural type LEDs AL 307 BM emit red light.
If Crystal led to illuminate the outside light, optical radiation quanta PRONI cabins in its zone p-n-junction. This results in a sharp decrease in reverse resistance PE Central and education potential difference between areas with different crystal MI conduction. Occurs, the so-called fotoJeDS, and on the findings LED potential difference appears.
Ток, который может развить во внешней цепи освещенный светом кристалл светодиода, очень мал, но разность потенциалов на выводах светодиода может составлять 0.6… 1.3 В. Конкретная величина ЭДС зависит от цвета свечения LED, его типа и величины нагрузочного сопротивления.
When the greatest impact experiments provide pechivali Red LEDs glow, in particular, domestic type LEDs AL 307 BM and AL 307 KM. Slightly less EMF develop green LEDs, for example, Al 307 VM (AL 307). It is a very wide range of values of EMF even among SWE todiodov of the same type.
On Fig.1 shows a schematic diagram of the [1]. The voltage generated by the indicator led lit LED, calls from the piranie transistor T1 type BC548B. The voltage on the collector of that transistor decreases. With a view to obtaining a more pronounced effect of operation of the appliance it can include multiple LEDs in series. However, the input resistance ing base transition of bipolar tranzisto RA T1 is small, and it is quite strongly and bypassing LED clearance, he fotoJeDS source.
Figure. 1
In Scheme Fig. 2 [1] fotoJeDS, developed with their light illumination LEDs will be much more. This is because field-effect transistor T1 has very high input resistance. LED, BU DUT work as a source of EMF in a holo tions for empty door. Two voltage red led diode if their coverage is enough for high-intensity light more naturally than od. Select the type of field-effect transistor T1 Pro data will be decrypted! lowest magnitude threshold voltage it unlocking. Among imported transistors such parameters have, for example, BS108, BS170 BSS138. If found to have a slight pain transistor circuits voltage cutoff you can instead of two "adoptive" LEDs use three or more. Relay RE1, included in the circuit flow field first transistor triggers illumination LEDs and can be used to include instruction on/off lighting or other electrical appliances.
Fig. 2
The use of LEDs as as Photodetectors were also dealt with in articles in [1-4].
Literature
- РЕ-AR. – 2016. – №4. – 30.
- Geoff Nicholls, LEDs double as photosensors // – 2009. – №12. – P.56.
- – 2010. – №1. – P.56.
- Евгений Яковлев. LED фотоприемник-индикатор для систем охранной сигнализации // Электрик. – 2011. – №4. – С.84-85.
Author: Andrei Nikolaev, Zaporozhye
Source: Radioamator No. 4/2017
