Signal flashlight on solar cells. Scheme, description

Free technical library

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

Signal flashlight on solar cells. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

Comments on the article

Have you ever been in a situation where you would have needed any device that warned of danger, but there was none? For example, you dug a ditch around a flower garden or dug up a lawn in the spring and suddenly remembered that you had guests in the evening. Maybe you're building a pool or have a large pothole at the entrance to your property. Regardless of the specific situation, there are times when a device is required to warn of danger.

The purpose of a warning system is to attract attention; flashes of light rather than constantly burning lights attract human attention most effectively, because the human eye perceives them as movement (change). We all know that human vision is much more sensitive to moving objects than to stationary ones.

The flashing warning light described in this chapter is designed specifically to attract attention in the event of any danger.

The principle of operation of the circuit

The security circuit is built using a single integrated circuit LM3909. This microcircuit is a unique pulse generator that consumes very little power and requires a minimum of additional elements. The simplicity of the device of a flashing flashlight can be judged from the diagram in Fig. 1, requiring only four attachments.

Solar signal flashlight
Ris.1

The microcircuit is essentially a negative resistance oscillator, the pulse repetition period of which is determined by the internal elements and the capacitance of the capacitor C1. At the moment the power is turned on, the capacitor C1 begins to charge. The charge rate and hence the time constant is set and controlled by IC1. When the voltage on the capacitor reaches the set trigger level, IC1 turns on and discharges the capacitor C1 to the LED LED1.

When the capacitance is discharged through the diode, the current flows through the base of the transistor Q1, which goes into saturation mode. Resistor R1 limits the discharge current of capacitor C1 and determines the time constant of the discharge cycle, which in turn determines the on-time of the transistor. With a large resistance of the resistor, the capacitor discharges more slowly and the time constant increases, and with a small resistance, it decreases.

A warning lamp is connected in series with the switching transistor, therefore it lights up when the transistor conducts current.

When the voltage on the capacitor falls to the set lower limit, IC1 goes into its initial state and the capacitor C1 begins to charge again. The cycle of work is repeated.

The ratio of on and off durations (duty cycle) is determined by the ratio R1/C1 Our circuit is designed so that the lamp is on for approximately 6% of the full cycle time. This corresponds to about 15 flashes of light in 1 minute.

Source of power

Although the flashlight's circuitry is powered by a solar panel, its main purpose is to warn of danger at night, when our vision is much less efficient and it is quite possible to run into any obstacle. Therefore, it is necessary to store energy during the day for later use at night.

For this, nickel-cadmium batteries were selected, which are preferable to lead-acid batteries due to the presence of a relatively constant discharge voltage. It would be very inappropriate if the brightness of the light decreased at night as the battery was discharged. When using nickel-cadmium batteries, the illumination remains bright until deep discharge.

In total, five AA nickel-cadmium batteries with soldered leads are required to power the circuit, each of which can store 0,5 Ah of electricity.

The elements are soldered to each other with opposite leads: the positive lead of one element is soldered to the negative lead of the next. Then a sheet of thick paper serving as a case is wrapped around the battery and the entire product is filled with a suitable polymer composition in order to provide reliable moisture insulation.

Solar battery

Nickel-cadmium batteries are solar charged. For this design, crescent-shaped elements are selected, obtained by cutting segments of a round element with a diameter of 10 cm, in order to give it a square shape. The output current of these elements lies in the range of 50 - 80 mA, although there are elements that develop a current of 125 mA or more.

The main task solved by this solar battery design is to maintain nickel-cadmium batteries in a constantly charged state without recharging. As shown in Chap. 10, Nickel-cadmium batteries are easily damaged when overcharged.

The disk batteries used in this design can be charged with a current of 50 mA without fear of damaging them. Thus, we will make a solar battery that generates a current of about 50 mA.

The danger warning flashlight is small in size, so it is better to make a small solar panel. For this purpose, crescent-shaped elements should be selected that develop a current of 90 - 100 mA.

Divide the crescent elements in half. This is easily done by sharply pressing the cross-shaped blade of a knife on the area near the straight edge of the element. The original round elements, from which the crescent-shaped elements were chipped off, were obtained from a crystalline material in which the cleavage lines are perpendicular to the straight edges of the crescent-shaped elements. If you click on this edge, the element will split into two parts. The dimensions of the resulting elements are determined by where the click is made. If you click in the middle, you will get two identical elements.

As you know, the division of the element into segments does not destroy it, but only reduces the output current. Therefore, when the element is divided in half, each half will generate a current of 45-50 mA.

It is not necessary to divide the elements into parts, you can use whole sickle-shaped elements that generate a current of only 50 mA. For the selection of such elements, it is useful tester. It must be remembered that low-current cells will take up more space in the battery.

Connect 14 elements in series - and you get a solar battery. Place them on a small piece of plastic or glass and seal them against the environment.

The blocking diode (D1) protects the batteries from being discharged by the solar panel at night. It is a germanium diode with a low forward voltage of about 0,3 V and a maximum current of 200 mA.

Signal light design

The electronic circuit is made using printed wiring. The printed circuit board is shown in fig. 2, placement of parts - in fig. 3. There is nothing complicated in manufacturing, just carefully observe the polarity of the terminals of all semiconductor devices and carefully solder the connections.

Solar signal flashlight
Ris.2

Solar signal flashlight
Ris.3

A flashing lamp must be placed in a glass container to protect it from the effects of the external environment. In addition, the glass bulb helps diffuse the light of the lamp over a wide range of angles. For this purpose, a spherical diffuser, previously used in the parking lights of some cars, is perfect. Covered with a similar cap, the lamp is visible from all directions.

It is also possible to place the lamp between two lenses, a design commonly used in roadside guard lights. Lenses don't have to be round, any shape will do. It will not be difficult to protect the lamp in accordance with the recommendations given.

I myself, however, specifically needed a small signal torch that would shine in only one direction. As a result of the search, I found a cheap illuminator for sale that exactly met my requirements (see the parts list for more details). It was intended for use in a car and was equipped with a magnetic holder (very convenient for attaching to metal surfaces) and a connector for plugging into a 12 V cigarette lighter socket.

In order to use this flashlight as a signal light, the first step was to cut the connecting drive with the 12-volt plug so that a piece of wire about 10 cm long was attached. Save the cigarette lighter plug and connecting wire if desired for future construction. Now remove the wire winding handle by unscrewing the screw holding it.

The bulb in this flashlight is rated for 12 V and will not work well in our circuit. To access the bulb, unscrew the outer ring holding the front glass of the flashlight counterclockwise. Replace the lamp with lamp #50 and assemble the flashlight.

The printed circuit board shown in fig. 2 is specially sized to fit exactly in the recess of the 12-volt connector.

The board and all the details on it fit exactly in size, except for the capacitor C1, which must be positioned "lying down".

Finally, solder the leads of the lamp, battery, and solar panels to the appropriate pads on the board. During the final assembly, the flashlight is fixed on the battery. The extra weight of the battery will add stability to the flashlight. The solar battery, which is not attached to the flashlight, can be located in any place illuminated by the sun.

Using a beacon

The flashlight may not be supplied with a toggle switch to turn it off during the daytime. It is not necessary. My experience shows that a freshly charged set of batteries is enough for a week of flashlight operation. Completely discharged nickel-cadmium cells are fully recharged in 10 hours of sunshine, in other words, in a day and a half of solar battery operation.

If this mode of operation does not satisfy you, you should increase the size of the solar array so that it generates a current of 17 mA, and change the old battery cells to cells with a higher capacity (type C). In this case, approximately 3 times more energy will be stored.

The scope of this small portable flashlight is almost unlimited. Of course, the already mentioned applications immediately come to mind: timely light warning of depressions and pits, hedges that are difficult to see and imperceptible obstacles. It is also a good idea to install signal lights on boats, marinas and tall buildings.

If you are a radio amateur, you may want to mount a flashing flashlight with a spherical cap on your antenna mast. Housewives will love using a device like this to alert you to freshly rubbed floors. A flashlight with a magnetic holder can be attached to the roof of a car parked on the side of a highway.

And what a funny mask with twinkling eyes will turn out thanks to such a flashlight!

Author: Byers T.

See other articles Section Alternative energy sources.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Energy from space for Starship 08.05.2024

Producing solar energy in space is becoming more feasible with the advent of new technologies and the development of space programs. The head of the startup Virtus Solis shared his vision of using SpaceX's Starship to create orbital power plants capable of powering the Earth. Startup Virtus Solis has unveiled an ambitious project to create orbital power plants using SpaceX's Starship. This idea could significantly change the field of solar energy production, making it more accessible and cheaper. The core of the startup's plan is to reduce the cost of launching satellites into space using Starship. This technological breakthrough is expected to make solar energy production in space more competitive with traditional energy sources. Virtual Solis plans to build large photovoltaic panels in orbit, using Starship to deliver the necessary equipment. However, one of the key challenges ... >>

New method for creating powerful batteries 08.05.2024

With the development of technology and the expanding use of electronics, the issue of creating efficient and safe energy sources is becoming increasingly urgent. Researchers at the University of Queensland have unveiled a new approach to creating high-power zinc-based batteries that could change the landscape of the energy industry. One of the main problems with traditional water-based rechargeable batteries was their low voltage, which limited their use in modern devices. But thanks to a new method developed by scientists, this drawback has been successfully overcome. As part of their research, scientists turned to a special organic compound - catechol. It turned out to be an important component that can improve battery stability and increase its efficiency. This approach has led to a significant increase in the voltage of zinc-ion batteries, making them more competitive. According to scientists, such batteries have several advantages. They have b ... >>

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, ... >>

Random news from the Archive

Contact lenses with iris scanner 09.06.2015

The United States Patent and Trademark Office (USPTO) has granted Google Patent #9,047,512 for "Contact Lenses".

Behind the common name is an iris scanning system. Integrated sensors collect information about how the iris reflects incident light. This allows you to create a "digital portrait" of the eye for later use as an identifier.

It is assumed that the lenses will consist of several layers. In particular, sensors will be located on one of them, and a microcontroller on the other. A "sandwich" of these layers is proposed to be enclosed in a polymer shell.

It should be noted that the layer with sensors can theoretically contain a wide variety of sensors. They can be used to assess temperature, pH, alcohol content, cholesterol levels, etc.

Of course, contact lenses can simultaneously perform their main function - to correct vision.

Other interesting news:

▪ The ozone hole must disappear

▪ New DVD recording format proposed

▪ Philips Xenium E580 Super Standalone Mobile Phone

▪ Star farthest from Earth discovered

▪ Neolithic art gallery in Somalia

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Electric meters. Article selection

▪ article Man is what he eats. Popular expression

▪ article Who and where managed to survive and not become disabled after his brain was pierced by an iron rod? Detailed answer

▪ article Locksmith of emergency repair work. Standard instruction on labor protection

▪ article Digital multimeter measures temperature. Encyclopedia of radio electronics and electrical engineering

▪ article Recharging the battery 7D-0,125D from the network charger. 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