This solar photovoltaic power supply unit for breadboard circuit experiments, the circuit is shown in the figure. 
A solar cell, also called a solar photovoltaic film, is a device that converts solar energy directly into electrical energy due to the photovoltaic effect, and is also a semiconductor photodiode. At present, solar photovoltaic wafers on the market are generally silicon solar cells, and the conversion efficiency is about 10%.
There are a variety of solar PV chips available under amateur conditions. This circuit power supply is mainly used for breadboard experimental circuit, the output voltage is required to be 3 ~ 6V, the output current is generally about 10mA; therefore, a 9V voltage, nominal 100mA current photovoltaic chip is used for power supply.
The principle of the power supply is to convert solar energy into electrical energy and store it for use in circuit experiments. Generally, the battery can be charged.
Considering that this circuit is mainly used for breadboard circuit experiments, capacitors are used to store electrical energy.
Supercapacitor is called super capacitor, also known as Farad capacitor and gold capacitor. It is a special capacitor specially used for energy storage. It has a large capacitance of 0.1 to 5000F. This circuit uses a capacitor with a withstand voltage of 5.5V and a capacity of 1F. Compared with the battery, the main advantages of the super capacitor are: low impedance; long life, more than 400,000 charge and discharge, no "memory effect"; fast charging speed, more than 95% of its rated capacity after charging for 10 seconds to 10 minutes; The circuit is simple and requires no maintenance or maintenance.
The circuit outputs 3 to 6V DC voltage. Why use 9V, 100mA PV chips? This is mainly because the machine is mainly used indoors, the light is weak; in order to be able to charge near the window during the day and charge under the electric light at night, the use of photovoltaic chips with higher output voltage can meet the needs.
The supercapacitor has a withstand voltage of 5.5V. In order not to cause the voltage to exceed the upper limit of the capacitor's withstand voltage when the light is strong for a long time, the circuit adopts a voltage stabilization measure. The circuit is connected in parallel with two blue LED lights connected in series at both ends of the photovoltaic chip. The operating voltage of the blue LED is 3.3V, and the two series are 6.6V. This voltage is applied to the super capacitor through the diode D1, which can stabilize the upper limit of the charging voltage to about 6V; although the voltage resistance of the supercapacitor exceeds 0.5V, But it does not affect the normal use of the circuit.
The current that the circuit can supply is inversely proportional to the power supply time. The higher the current, the shorter the power supply time. If 2F storage capacitor is used, the discharge current is 10mA, and the discharge voltage is reduced from 6V to 3W. How long can it be supplied? It can be calculated using the following formula:
Time T=C(U1-U2)/1 where T is time and the unit is s; C is the capacitor capacity, the unit is F; U1 is the voltage at which the capacitor discharge starts, the unit is V; U2 is the voltage at the end of the capacitor discharge, The unit is V; I is the discharge current, and the unit is A. Then there are:
Time T = 2 (6-3) / 0.01 = 600 (seconds) = 10 (minutes) The answer is that it can be powered for 10 minutes. It should be noted that the above is the result of assuming that the discharge current in the circuit is kept constant at 10 mA; if the actual situation is different, the discharge time is corrected according to various factors.
Although the super capacitor can provide instantaneous high current to the load, its DC internal resistance is still relatively large; if it is used in an AC circuit, a bypass capacitor should be added; the function of the electrolytic capacitor C3 in the circuit can improve the AC performance of the super capacitor power supply.
First, assembly and assembly of breadboard solar photovoltaic power supply, should choose a cylindrical super capacitor, it has two parallel pins, can be directly inserted on the breadboard.
A 90mm x 42mm photovoltaic sheet can be used in amateur conditions. On the back there are two copper-clad plates with the polarity of the battery.
On the back side of the solar photovoltaic sheet, two red and black leads are respectively soldered on the positive and negative electrodes of the battery, and then the photovoltaic sheet is pasted on a KT board with double-sided tape.
1/4 of the breadboard can be used according to the size of the components installed; cut the breadboard and keep a lower strip with a dovetail hook and stick it in place on the KT board.
The voltage regulator uses two 3mm LEDs to assemble the breadboard solar photovoltaic power supply according to the circuit. Then it is placed in the sun, and after a few minutes, it will be found that the blue LED is bright, indicating that it is charging; the degree of charging can be judged according to the brightness of the LED. The device can be charged in the sun for about 5 minutes.
Second, the application experiment will be successfully assembled breadboard circuit with dovetail slot and solar photovoltaic power supply device fixed, and then use the bread line from the solar photovoltaic power supply connected to the experimental breadboard, you can carry out solar photovoltaic power supply Experimented.
The experimental circuit for power supply of solar photovoltaic power supply is shown in the figure below. The operating current is about 3 mA, and the device can provide about 40 minutes of experimentation. This is basically consistent with the calculation results. If you want to increase the power supply time of the photovoltaic power supply, you can increase the capacity of the capacitor.
It has been found that the continuous working time of the device cannot be compared with the battery, but it can be charged at any time under daylight or light.
The shortcomings of current solar photovoltaic power supplies are relatively expensive.
Third, the PV chip measurement If you get a nominal 9V, 100mA solar photovoltaic film, you can use the meter to measure its output voltage and short-circuit current. The voltage can be measured directly from the DC limit of the voltmeter. The short-circuit current can be measured with a 200 mA block. A set of measured results is: at noon on sunny days, the photovoltaic film is perpendicular to the sunlight, and the short-circuit current is at most 55 mA. The maximum operating current of a photovoltaic wafer is generally slightly smaller than the short-circuit current, but the phase is similar; the short-circuit current is an important basis for designing a solar photovoltaic power source.
In addition, you can also measure the data of the following sets of photovoltaics: the output voltage under the illumination of the indoor window and the short-circuit current: the output voltage under various lighting fixtures, short-circuit current, etc.
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