LONG LIFE BATTERY-Most optoelectronic devices
Most optoelectronic devices
Most optoelectronic devices can react to visible light like human eyes.Some photoelectric devices can be used as energy sources when they are irradiated by sunlight or artificial light sources.Some optoelectronic devices are powered by conventional power sources.As an electronic control device, its various actions are excited and controlled by the presence, absence, strength, weakness or various frequencies of light waves.
In many ways, light is similar to the propagation of radio waves, photoelectric devices are similar to radio receivers, and can directly respond to received information.After understanding this series of properties of light, it will be easier to master the working principle of the photoelectric device, and make further experiments on the functions and electronic circuits of the photoelectric device by controlling the intensity, optical path and propagation of light.
Chapter II Solar Cells and Related Devices
When people talk about solar cells, it often means a device that converts sunlight into voltage.However, there are many other devices that have similar characteristics, so to be more precise, they are called " photocells".One thing they have in common is that when a specific light is input to these devices, a reaction corresponding to the input light will occur.Therefore, photovoltaic cells can also be called transducers, which can convert energy from one form to another.A common audio speaker is the best example of energy conversion, which converts energy from one form ( electrical energy ) to another ( audio output ).Photovoltaic cells use light from the sun or other light sources as their input.There are many output forms, depending on the type of device used.
Most people say solar cells are actually more specifically photovoltaic cells, because solar cells are made of photovoltaic materials and generate voltage when exposed to light.The main substances exhibiting this effect are selenium, germanium and silicon.Fig. 2 - 1 is a typical graph 2 - 1 describing how a photovoltaic cell or a solar cell works. the working principle of the photovoltaic cell is shown in fig. 2 - 1
The rheostat in the diagram represents the electrical load. When light strikes the surface of the battery, the current starts to flow. The magnitude of the current is related to the light's intensity.I degree is proportional to frequency.Current flows from the negative electrode to the positive electrode of the battery. Solar cells, like dry cells, are polar devices. For this reason, solar cells can be directly used as substitutes for ordinary cells, but their load cannot exceed the rated capacity of solar cells.Photovoltaic cells convert light energy into electrical energy, so it is also a transducer that converts energy from one form to another.
Another device to be introduced in this book is called " photoelectric conduit", which is often called photocell when it is sold on the market, but readers must not confuse this photocell with the photovoltaic cell described above, which is often also called solar cell, and the working principle of the two is completely different.
Generally, the photoelectric tube is made of cadmium sulfide, and its surface is treated. When light is irradiated, its resistance is variable, and the change of resistance is proportional to the intensity of light.Therefore, cadmium sulfide [ CDS ] is a device whose resistance varies with the intensity of the irradiation light.When light I impinges on its surface, the resistance of the device drops;When the intensity of light decreases, its resistance increases.Therefore, it can be considered that resistance is inversely proportional to the intensity of light, and conductance is directly proportional to the intensity of light.As the light intensity increases, the conductance also increases.
Fig. 2 - 2 shows the working principle of the typical circuit of the photoelectric catheter. it must be noted that the photoelectric catheter of fig. 2 - 2 is buried in the electronic circuit
Since photovoltaic cells can convert light energy into electrical energy, and cadmium sulfide itself cannot convert or generate electrical energy, a separate power supply must be provided in the circuit.In this example, the power supply is one to one dry cell, and the magnitude of the current is controlled by the internal resistance of the cadmium sulfide element.
In the previous circuit ( fig. 2 - 1 ), the magnitude of the current in the photovoltaic circuit is controlled by light.In the circuit of photoelectric conduit, light can also control the magnitude of current.However, the current is controlled by changing the magnitude of the resistance.The only drawback of the photoelectric conduit circuit is that the power supply will run out sooner or later. As long as the intensity of light changes, the CDS device will continue to change its conductance, but after the dry battery is discharged, the change in resistance will no longer have any effect on the circuit.In the circuit of photovoltaic cells, the circuit will function as long as the surface of the cell is irradiated by fluorine.When the light disappears, control stops.As long as there is some form of light, photovoltaic cells will never stop running.
Just as photovoltaic cells have another name, ODS devices or photoelectric conduits are also commonly referred to as photoresists.It is of course appropriate to call it a photoconductor, but it seems more common to call it a photoresistor.
Both photoelectric devices work according to the photoelectric effect.Photoelectric effect is a phenomenon in which atoms in some substances change temporarily under the action of light.Some materials have resistance changes, like CDS devices;Some materials generate voltages, such as photovoltaic cells.