Flashlight on the elements of a solar battery and methods for its improvement. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

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On fig. 1.8 shows the appearance of a decorative lamp with 4 RS5415.5 elements connected in series, a 1400 mAh AA battery and a charging control device.

There are other designs that differ in appearance (for example, designed for "sticking" (vertical mounting) directly into the ground in a summer cottage. The purpose of different types of lamps may be different, the capacity of the batteries and their type (as well as the power of the solar battery) is different depending on the design, but the principle of operation is the same for all.In clear weather with high solar activity (during the day), the device, using the photocells of the solar battery, converts solar energy into electric current, which charges low-power batteries.When it gets dark, natural solar activity decreases, charging batteries are terminated.

Fig.1.8 Decorative luminaire with 4 elements connected in series RS5415 5

The internal circuit "feels" the onset of dusk and enables the flickering of the light element, which is the orange LED. Structurally, the LED is made in a tube of matte plastic so that it seems as if a candle is flickering inside the lamp housing. On fig. 1.9 shows the design of the matte tube in the flashlight housing, in which the orange LED is "hidden".

Thanks to the design features of the case, successful aesthetic solutions, as well as the electronic circuit of the device that controls the LED with chaotic bursts of pulses, it was possible to obtain the effect of a flickering candle.

Progress in the field of new light elements is irreversible. About 10 years ago, special lamps were on sale everywhere (calculated for the E27 cartridge and the voltage of the lighting network was 220 V), which produced a similar effect of a flickering candle due to the inert (neon) gas in the lamp bulb. Today, the same effect can be obtained from the LED.

The cost of such lanterns-lamps is small and ranges from 3 to 10 € (Euro). In Russia and neighboring countries, such lamps are sold in the departments of electrical goods, souvenirs and hypermarkets.

Fig.1 9. Design of a frosted tube with an orange LED

Consider the electrical circuit of the device and its main elements.

Principle of operation of the device

The electrical circuit of the device is shown in fig. 1.10.

Fig.1 10. Electrical diagram of a flashlight with a flickering light and automatic recharging from solar panels

Chip DA1 is structurally "flooded" and on the printed circuit board is a drop of a solid composition with three pins. The function of this microcircuit is the generation of pulses with a chaotic repetition rate and duty cycle. As soon as it receives power by closing the electrical circuit with the SB1 switch, chaotic pulses of positive polarity with an amplitude of 3-1,5 V are present at pin 1,6 DAI "OUT" (with normally charged batteries). The limiting resistor R3 limits the current through the HL1 LED, which performs the energy-saving function of the device in the evening.

Pulses of a chaotic order from the output of the microcircuit enter the base of the transistor VT3, on which the current amplifier is implemented.

In turn, on transistors VT1, VT2, a photosensitive assembly (photo relay) is assembled that controls the operation of the current amplifier by recharging from solar panels.

VT2 and LED HL1. In clear weather or noticeable solar activity on a cloudy day (in short, in the daytime), the solar battery on the FB1-FB4 elements is a DC generator. The maximum total voltage on its elements (measured at the cathode of the VD1 diode and the common wire) is at least 3,4 V. This voltage enters the base of the transistor VT1 (connected together with VT2 according to the Darlington circuit - with the maximum voltage multiplication factor) through a voltage divider on resistors Rl, R4. That is, while it is light, the voltage on the solar battery is sufficient to open the transistor VT1, and, accordingly, lock VT2. No current flows through the transistor VT3, the LED does not flicker.

Batteries GB1, GB2 connected in series, when SB1 is closed, are charged with a small current through the VD1 diode, the second function of which is to prevent the batteries from discharging at night through the solar cells.

In the evening (dark) time of the day, when there is not enough natural light to charge the batteries, the photo relay on transistors VT1, VT2 allows current through the transistor VT3, the HL1 LED flickers, resembling a burning candle. In this case, a current of about 8 mA flows through the LED.

When the LED is off, the device practically does not consume current. Accordingly, well-charged batteries, provided that the LED is lit only in the evening and at night (that is, 1/2 day), would be enough for three days (approximately 88 hours).

However, the batteries are charged during the daytime, so in practice the operating time of a new flashlight increases a lot and depends (mostly) on solar activity during the daytime, that is, the battery charge current.

As a rule, the lantern is installed in the room on the window, so that it is better charged during the day. In practice, it is impossible to install a flashlight in the depths of the room, and even more so in dark interiors, since it will not be possible to obtain the desired level of battery charge and the possibilities of "endless operation" declared in the manual (operating instructions), since the LED resource is at least 100 hours "are not true. Of course, not because of the LED, but simply the device requires constant solar energy for recharging, which in a dark corner or room will have nowhere to get, and the batteries do not have an endless charge-discharge cycle. We will come to other noted shortcomings of the device and ways to localize them below.

On fig. 1.11 shows a view of the installation of solar cells inside the case.

Fig.1.11. Installation of solar cells inside the housing

About details

The device is equipped with AA Ni-Cd batteries with a nominal voltage of 1,2 V and a capacity of 700 mAh.

Transistors VT1-VT3 can be replaced with domestic devices such as KT312, KT343 with any letter index and similar.

Recommendations for improving work

To improve the operation of the device, which includes long-term uninterrupted operation for several months in a row (and not several days, as before completion), it is necessary to make a number of simple changes in the circuit.

• In parallel with the VD1 diode, install 2 more similar diodes to increase the battery charge current. The main thing is that all three diodes are similar.
• Replace batteries with Ni-Mh (this will extend their useful life) in the same AA package, but with a capacity of 1400 mAh or more.
• Remove resistor R4 from the circuit. In this case, the photorelay will work earlier, already at minimum illumination and turn on the LED later (at dusk), which contributes to a longer charge of batteries, especially with a larger capacity than standard ones.
• During the day, it is better to operate the lantern (as already noted above) in the most illuminated places (for example, on the window), and by night, on the eve of a romantic dinner, you can move it deep into the room, which will add romance and originality to the atmosphere of human communication.

On fig. 1.12 presents portable solar-powered lamps with a built-in battery.

Rice. 1.12. Solar-powered portable lamps with built-in battery

Range of application

The range of application in everyday life and outdoors of solar cells and miniature solar batteries based on them is very diverse.

For example, 2-3 solar panels built into the shoulder strap of a digital camera or camera will not allow you to fully charge the battery of the device, but they will be enough to power the battery and not allow the traveler to be left without the opportunity to take pictures in nature, far from civilization , where there is simply nothing to recharge a miniature battery, except for natural sunlight.

To do this, the strap is attached to the camera in the usual way. A small wire is taken away from it, which is connected to the camera through the DC-out connector for external power supply. Such a belt can be used to recharge the battery for 10-12 hours, subject to solar activity.

Author: Kashkarov A.P.

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