Do-it-yourself LED flashlight. Let's make an LED lamp together with our own hands. Required elements for manufacturing
LED strips are now used everywhere and sometimes pieces of such strips, strips with LEDs burned out in places, fall into the hands. And there are a lot of whole, working LEDs and it’s a pity to throw away such goodness, I want to use them somewhere. There are also various types of batteries. In particular, we will consider the elements of a "dead" Ni-Cd (nickel-cadmium) battery. From all this rubbish, you can build a solid home-made lantern, with a high probability better than the factory one.
LED strip how to check
As a rule, LED strips are rated for 12 volts and consist of many independent segments connected in parallel to form a strip. This means that if any element fails, only the corresponding element loses its functionality, the remaining segments of the LED strip continue to work.
Actually, you just need to apply a supply voltage of 12 volts to special contact points that are on each piece of tape. In this case, the voltage will go to all segments of the tape and it will become clear where the non-working sections are.
Each segment consists of 3 LEDs and a current limiting resistor connected in series. If you divide 12 volts by 3 (number of LEDs), you get 4 volts per LED. This is the supply voltage of one LED - 4 volts. I emphasize, since the resistor limits the entire circuit, a voltage of 3.5 volts is enough for the diode. Knowing this voltage, we can directly test any LED on the tape individually. This can be done by touching the leads of the LED with probes connected to a power supply with a voltage of 3.5 volts.
For these purposes, you can use a laboratory, regulated power supply or mobile phone charger. The charger is not recommended to be connected directly to the LED, because its voltage is about 5 volts and theoretically the LED can burn out from a large current. To prevent this from happening, you need to connect the charger through a 100 ohm resistor, so we will limit the current.
I made myself such a simple device - charging from a mobile with crocodiles instead of a plug. It is very convenient for turning on cell phones without a battery, recharging batteries instead of a "frog" and other things. Good for testing LEDs too.
For the LED, the polarity of the voltage is important, if you confuse the plus with the minus, the diode will not light up. This is not a problem, the polarity of each LED is usually indicated on the tape, if not, then you need to try this and that. From the confused pluses or minuses, the diode will not deteriorate.
LED lamp
For a flashlight, it is necessary to make a light-emitting unit, a lamp. Actually, you need to dismantle the LEDs from the tape and group them according to your taste and color, by quantity, brightness and supply voltage.
To remove from the tape, I used a utility knife, carefully cutting off the LEDs directly with pieces of the conductive wires of the tape. I tried to solder, but something I did badly succeeded. Having picked 30-40 pieces, I stopped, more than enough for a flashlight and other crafts.
Connect the LEDs according to a simple rule: 4 volts per 1 or several diodes in parallel. That is, if the assembly is powered from a source of no more than 5 volts, no matter how many LEDs there are, they must be soldered in parallel. If you plan to power the assembly from 12 volts, you need to group 3 consecutive segments with an equal number of diodes in each. Here is an example of an assembly that I soldered from 24 LEDs, dividing them into 3 consecutive sections of 8 pieces. It is rated for 12 volts.
Each of the three sections of this element is designed for a voltage of about 4 volts. The sections are connected in series, so the entire assembly is powered by 12 volts.
Someone writes that LEDs should not be connected in parallel without an individual limiting resistor. Maybe this is correct, but I do not focus on such trifles. For a long service life, in my opinion, it is more important to choose a current-limiting resistor for the entire element and it should be selected not by measuring the current, but by feeling the working LEDs for heating. But more on that later.
I decided to make a flashlight powered by 3 nickel-cadmium cells from a used screwdriver battery. The voltage of each element is 1.2 volts, therefore 3 elements connected in series give 3.6 volts. We will focus on this tension.
By connecting 3 battery cells to 8 parallel diodes, I measured the current - about 180 milliamps. It was decided to make a light-emitting element of 8 LEDs, just as it fits successfully into a reflector from a halogen spot lamp.
As a base, I took a piece of foil fiberglass about 1cmX1cm, it will fit 8 LEDs in two rows. I cut 2 separating strips in the foil - the middle contact will be "-", the two extreme ones will be "+".
For soldering such small parts, my 15-watt soldering iron is too much, or rather too big a sting. You can make a tip for soldering SMD components from a piece of 2.5mm electrical wire. To keep the new tip in place in the large hole in the heater, you can bend the wire in half or add additional pieces of wire to the large hole.
The base is tinned with rosin solder and the LEDs are soldered with polarity. Cathodes ("-") are soldered to the middle strip, and anodes ("+") to the extreme ones. The connecting wires are soldered, the extreme strips are connected by a jumper.
You need to check the soldered structure by connecting it to a 3.5-4 volt source or through a resistor to the phone charger. Do not forget about the polarity of the inclusion. It remains to come up with a flashlight reflector, I took a reflector from a halogen lamp. The light element must be securely fixed in the reflector, for example with glue.
Unfortunately, the photo cannot convey the brightness of the glow of the assembled structure, I’ll say from myself: it doesn’t blind very well!
Battery
To power the flashlight, I decided to use rechargeable batteries from a "dead" screwdriver battery. I took out all 10 elements from the case. The screwdriver worked on this battery for 5-10 minutes and sat down, according to my version, the elements of this battery may well be suitable for the flashlight to work. After all, a flashlight needs currents that are much smaller than for a screwdriver.
I immediately unhooked three elements from the common bundle, they will just give a voltage of 3.6 volts.
I measured the voltage on each element individually - all were about 1.1 V, only one showed 0. Apparently this is a faulty bank, it's in the trash. The rest will still work. Three cans will be enough for my LED assembly.
Having studied the Internet, I brought out important information for myself about nickel-cadmium batteries: the nominal voltage of each cell is 1.2 volts, the bank should be charged to a voltage of 1.4 volts (the voltage on the bank without load), it should be discharged at least 0.9 volts - if several cells are composed in series, then not less than 1 volt per element. You can charge with a current of a tenth of the capacity (in my case 1.2A / h = 0.12A), but in fact it can be large (the screwdriver is charged for no more than an hour, which means the charging currents are at least 1.2A). For training / recovery, it is useful to discharge the battery to 1 V with some load and charge again, so several times. At the same time, estimate the approximate operating time of the flashlight.
So, for three elements connected in series, the parameters are as follows: charging voltage 1.4X3=4.2 volts, nominal voltage 1.2X3=3.6 volts, charge current - which will give a mobile charger with a stabilizer of my manufacture.
The only not clear moment: how to measure the minimum voltage on discharged batteries. Before connecting my lamp, there was a voltage of 3.5 volts on three elements, when connected - 2.8 volts, the voltage is quickly restored when disconnected again to 3.5 volts. I decided this: at the load, the voltage should not fall below 2.7 volts (0.9 V per element), without load it is desirable that there be 3 volts (1 V per element). However, it will take a long time to discharge, the longer you discharge, the more stable the voltage, it stops dropping quickly on the lit LEDs!
I discharged my already discharged batteries for several hours, sometimes turning off the lamp for several minutes. As a result, it turned out 2.71 V with a connected lamp and 3.45 V without a load, I did not dare to discharge further. I note that the LEDs continued to shine, albeit dimly.
Charger for nickel-cadmium batteries
Now you should build a charger for a flashlight. The main requirement is that the output voltage should not exceed 4.2 V.
If you plan to power the charger from any source of more than 6 volts, a simple circuit on KR142EN12A is relevant, this is a very common microcircuit for regulated, stabilized power. Foreign analogue of LM317. Here is a diagram of the charger on this chip:
But this scheme did not fit into my idea - versatility and maximum convenience for charging. After all, for this device you will need to make a transformer with a rectifier or use a ready-made power supply. I decided to make it possible to charge batteries from a mobile phone charger and a computer USB port. For implementation, a more complicated scheme is required:
The field effect transistor for this circuit can be taken from a faulty motherboard and other computer peripherals, I cut it off from an old video card. There are plenty of such transistors on the motherboard near the processor and not only. To be sure of your choice, you need to drive the transistor number into the search and make sure from the datasheets that this is a field transistor with an N-channel.
As a zener diode, I took the TL431 chip, it is found in almost every charger from a mobile phone or in other switching power supplies. The outputs of this microcircuit must be connected as in the figure:
I assembled the circuit on a piece of textolite, immediately provided a USB socket for connection. In addition to the circuit, I soldered one LED near the socket to indicate charging (that voltage is being supplied to the USB port).
A few explanations for the diagram Since the charging circuit will be connected to the battery all the time, the VD2 diode is necessary so that the battery does not discharge through the stabilizer elements. By selecting R4, you need to achieve a voltage of 4.4 V at the specified control point, you need to measure it with the battery unhooked, 0.2 volts is a margin for drawdown. And in general, 4.4 V does not go beyond the recommended voltage for three battery cans.
The charger circuit can be greatly simplified, but it will only have to be charged from a 5 V source (the USB port of the computer meets this requirement), if the charger of the phone produces a higher voltage, it cannot be used. According to a simplified scheme, theoretically, batteries can be recharged, but in practice, batteries are charged this way in many factory products.
LED current limit
To prevent overheating of the LEDs, and at the same time reduce the current consumption from the battery, you need to select a current-limiting resistor. I picked it up without any devices, estimating the heat by touch and controlling the brightness of the glow by eye. The selection must be made on a charged battery, you should find the optimal value between heating and brightness. I got a 5.1 ohm resistor.
Working hours
I made several charges and discharges and got the following results: charging time - 7-8 hours, with the lamp continuously on, the battery is discharged to 2.7 V in about 5 hours. However, when turned off for a few minutes, the battery recovers a little and can work for another half an hour, and so on several times. This means that the flashlight will work for a long time if it does not shine all the time, but in practice it does. Even if you use it practically without turning it off, it should be enough for a couple of nights.
Of course, a longer time without interruption was expected, but do not forget that the batteries were taken from a "dead" screwdriver battery.
housing for lantern
The resulting device needs to be placed somewhere, to make some kind of convenient case.
I wanted to place batteries with an LED flashlight in a polypropylene water pipe, but the cans did not even fit into a 32 mm pipe, because the inner diameter of the pipe is much smaller. As a result, I settled on couplings for 32 mm polypropylene. I took 4 couplings and 1 plug, glued them together with glue.
By gluing everything into one structure, we got a very massive lantern, about 4 cm in diameter. If you use any other pipe, you can significantly reduce the size of the lantern.
Having wrapped the whole thing with electrical tape for a better look, we got this lantern:
Afterword
In conclusion, I would like to say a few words about the resulting review. Not every USB port of a computer can charge this flashlight, it all depends on its load capacity, 0.5 A should be enough. For comparison, cell phones, when connected to some computers, may show charging, but in fact there is no charge. In other words, if the computer charges the phone, then the flashlight will also charge.
The FET circuit can be used to charge 1 or 2 battery cells from USB, you just need to adjust the voltage accordingly.
The issue of energy saving is more relevant today than ever. Incandescent lamps consume a large amount of electricity, but they do not always provide proper lighting. They were replaced by LED street lights, home and car lights. Read on to learn how to make your own LED flashlight.
Tools:
Materials:
One of the easiest ways to make an LED lamp is to use a broken old housing and install separate LEDs into it. This allows you to make LED lights with your own hands without additional effort. But when the work is done from scratch, you have to work more carefully and responsibly. We bring to your attention three schemes at once, according to which you can make a powerful and economical diode lamp. In each of the proposed schemes, we recommend using LEDs with a power of 3 watts. You can choose the color of the glow at your discretion (warm or cold). But for the home, a warm color will be more pleasant, giving the room pastel colors. On the street, it is better to use a cold one - it will be a little brighter. Scheme of the LED lamp No. 1
Within 3.7-14 volts, this circuit shows excellent stability in operation. Note that efficiency may drop as voltage increases. At the output, you can set the voltage to 3.7 and maintain it throughout the entire range. Use resistor R3 to set the output voltage, but do not reduce it too much. It is necessary to calculate the maximum current on LED1-LED, as well as the maximum allowable voltage on LED2. If your flashlight is powered by a Li-ion battery, then the efficiency will be 90-95%. 4.2 volts provide efficiency within 90%. 3.8 - 95%. You can calculate with a simple formula: P \u003d U x I. The selected LED will draw 0.7 A at 3.7 volts. We make a miscalculation: 0.7 x 3.7 \u003d 2.59 watts. Subtract the battery voltage from the resulting number and multiply by the current consumption: (4.2 - 3.7) x 0.7 \u003d 0.35 W. And now you can easily find out the exact efficiency: (100 / (2.59 + 0.37)) x 2.59 = 87.5%. Powerful LEDs must be installed on the radiator. It can be taken from a computer power supply. You can use the following arrangement of parts:
Please note that the transistor does not touch the board. Do the following:
Scheme of the LED lamp No. 2
The second option is quite economical. You will need KT819, KT315 and KT361. Using them, you can make a good stabilizer, although the losses will be slightly larger than in the previous version. The scheme is quite similar to the first, but everything is done exactly the opposite. The voltage is supplied by capacitor C4. The main difference is that the output transistor is opened by resistor R1 and KT315. In the first scheme, only KT315 closes and opens. All parts should be located as follows:
An additional LED provides good stabilization. The following information will help you create other low voltage regulators.
Scheme of the LED lamp No. 3
The last considered scheme allows you to significantly increase the efficiency, get a higher brightness of the glow. In this case, you will need four batteries with a total capacity of at least 13 Ah and an additional focus lens for LEDs. In this case, there is no need for an additional LED. Everything is done in SMD design without transistors, which consume additional energy. Thanks to this, the battery life is significantly increased. The stabilizer can be TL431. In this case, the efficiency can vary from 90 to 99 percent, which is more than good. At the output, it is best to set the power to 3.9 volts. In this case, the LEDs will not burn out for many months, or even years. Although it is quite possible a slight heating of the radiator. But it normal. Make a flashlight from 1.5 VIf you do not need to understand complex circuits to get a powerful lighting fixture, we also offer an easy way to make the simplest (albeit rather weak) LED lights for your home. This lamp is enough for home use. To simplify the task, you can take an old flashlight with an incandescent lamp and work with it. The procedure is as follows:
When the circuit is ready, the diode shines with maximum brightness and everything works, you can proceed to the finishing work.
The made flashlight can work fully and for a long time even on a discharged battery. If there is no battery at all, the light will light up even from a non-standard battery. For example, if you insert two wires from different metals into a potato and connect an LED. Not the fact that you will need this method, but the cases are different. LED lights have received good reviews from customers due to their low power consumption, low cost and reliability. Incandescent lamps are far from the best option today. And now you know how to make an LED flashlight yourself from improvised means. |
More recently, the word LED was associated only with indicator devices. Since they were quite expensive and emitted only a few colors, they also shone faintly. With the development of technology, the price of LED products has gradually decreased, the scope of application has expanded in leaps and bounds.
Today they are used in various devices, they are used almost everywhere where lighting devices are needed. Headlights and lamps in cars are equipped with LEDs, advertising on billboards is highlighted by LED strips. At home, they are also no less often used.
Reasons for using LEDs
Not spared and lanterns. Thanks to powerful LEDs, it became possible to assemble a heavy-duty and at the same time quite autonomous flashlight. Such lanterns can emit very strong and bright light over a long distance or over a large area.
In this article, we will tell you about the main advantages of high power LEDs, and tell you how to fold an LED flashlight with your own hands. If you have already encountered this, then you can supplement your knowledge, for beginners in this area, the article will answer many questions related to LEDs and lanterns with their application.
If you want to save money by using an LED, there are a few things to consider. Since sometimes the price of such a lamp can exceed all the savings. If, on the other hand, you have to spend a lot of money and time maintaining lights, and the total amount of them consumes a lot of electricity, then you should consider whether an LED would be a better replacement.
Compared to conventional lamps, the LED has a number of advantages that elevate it:
- There is no need for maintenance.
- Significant energy savings, sometimes saving up to 10 times.
- High quality light output.
- Very high service life.
Necessary components
If you decide to assemble an LED flashlight with your own hands, for moving in the dark or for working at night, but do not know where to start? You will help you with this. The first thing to do is to find the necessary elements for assembly.
Here is a preliminary list of required parts:
- Light-emitting diode
- Winding wire, 20-30 cm.
- Ferrite ring approximately 1-.1.5 cm in diameter.
- Transistor.
- 1000 ohm resistor.
Of course, this list also needs to be supplemented with a battery, but this is an element that can be easily found in any home and does not require special preparation. You should also choose a case or some kind of base on which the entire circuit will be installed. A good case would be an old non-working flashlight or one that you are going to modify.
How to assemble with your own hands
When assembling the circuit, we will need a transformer, but it was not added to the list. We will make it with our own hands from a ferrite ring and wire. It is very simple to do this, we take our ring and start winding the wire forty-five times, this wire will be connected to the LED. We take the next wire, and wind it thirty times already, and send it to the base of the transistor.
The resistor used in the circuit must have a resistance of 2000 ohms, only using such a resistance, the circuit will be able to work without failure. When testing the circuit, replace the resistor R1 with a similar one with adjustable resistance. Turn on the entire circuit and adjust the resistance of this resistor, adjust the voltage to around 25mA.
As a result, you will find out what resistance should be at this point, and you will be able to choose a suitable resistor, with the resistance value you need.
If the circuit is drawn up in full accordance with the above requirements, then the lamp should work immediately. If it doesn't work, then you may have made the following mistake:
- The ends of the winding are connected in reverse.
- The number of turns is not correct.
- If there are less than 15 wound turns, then the current generation in the transformer ceases to be carried out.
Assembling a 12 volt LED flashlight
If the amount of light from the flashlight is not enough, then you can assemble a powerful flashlight powered by a 12 volt battery. Such a flashlight is still portable, but much larger in size.
To assemble the circuit of such a lantern with our own hands, we need the following parts:
- Plastic pipe, about 5 cm in diameter and PVC glue.
- Threaded fitting for PVC, two pieces.
- Threaded plug.
- Tumbler.
- Actually the LED lamp itself, designed for 12 volts.
- Battery for powering the LED, 12 volts.
Insulating tape, heat shrink tubing and small clamps to tidy up the wiring.
The battery can be made by hand, from small batteries that are used in radio-controlled toys. You may need 8-12pcs, depending on their power, so that in total you get 12 volts.
To the contacts on the light bulb, solder two wires, the length of each should exceed the length of the battery by several centimeters. Everyone is carefully isolated. When connecting the lamp and battery, install the toggle switch in such a way that it is located at the opposite end from the LED lamp.
At the ends of the wires coming from the lamp and from the battery pack, which we made with our own hands, we install special connectors for easy connection. We collect the entire circuit and check its performance.
Assembly diagram
If everything works, then proceed to the creation of the case. Having cut off the required length of the pipe, we insert our entire structure into it. Accumulator We carefully fix it inside with glue so that it does not damage the light bulb during operation.
We install a fitting at both ends, fasten it with glue, so we will protect the lantern from accidental moisture getting inside. Next, we bring our toggle switch to the opposite edge from the lamp, and also carefully fix it. The rear fitting must completely cover the switch with its walls, and when the plug is screwed in, prevent moisture from entering there.
To use, just unscrew the cap, turn on the flashlight and tighten it again tightly.
price issue
The most expensive thing you will need is a 12 volt LED lamp. It costs about 4-5 dollars. After digging through old toys of children, batteries from a broken car will be free for you.
A toggle switch and a pipe can also be found in the garage; cuts of such pipes constantly remain after repairs. If there are no pipes and batteries, you can ask friends and neighbors or buy in a store. If you buy absolutely everything, then such a flashlight can cost you about $ 10.
Summarize
LED technology is gaining more and more popularity. Having good characteristics, they can soon completely displace all competitors in the field of lighting. And to assemble a powerful portable flashlight with an LED lamp with your own hands will not be difficult for you.
A flashlight is a necessary thing when traveling to nature or out of town to the country. At night, on a personal plot or near a tent, only he will create a ray of light in a dark kingdom. But even in a city apartment, sometimes you just can’t do without it. As a rule, it is difficult to get something small and rolled under a bed or sofa without a flashlight. And although there are devices nowadays that are multifunctional and can be a source of light, some of our readers will surely want to know how to make a flashlight with their own hands. How to make a small device from improvised items will be described later.
Classic form
The most convenient design, which, in principle, has remained unchanged for flashlights for many years, is a design that contains:
- cylindrical body with batteries of the same shape;
- a reflector with a light bulb at one end of the housing;
- removable cover from the other end of the case.
And this design can be obtained using unnecessary household items. If you make a lantern with your own hands, of course, there will be no beauty of forms like that of an industrial design. But it will be functional and a lot of positive emotions will be received from a working homemade product.
So, the main problem, which at first glance is difficult to solve, is the reflector. But it just seems complicated. In fact, we are surrounded by many objects that can become a blank for a number of reflectors of different sizes. These are ordinary plastic bottles. Their inner surface near the neck is very close in shape to that which has a reflector made at the factory. And the lid is as if created to mount an LED in it, which today is the best light source. It is brighter and more economical than a miniature light bulb.
We make a reflector
It is not a problem that you can not find a tube of suitable dimensions for making a case. It can be glued from individual parts. For example, from unnecessary disposable ballpoint pens. To spring the contacts, you can use a spiral, which is used for page bindings, and make contacts from thin sheet metal, the raw material for which will be a tin can. Therefore, we start by choosing a plastic bottle of the desired size and selecting the remaining elements. The smaller the bottle, the more rigid and strong the reflector will be. Fastening parts during assembly is easiest to do on the basis of building sealant.
So, let's start making a flashlight with our own hands. Cut off the neck and the parabolic part of the body from the bottle with a sharp knife and trim the edges with scissors.
For effective reflection, we use the foil in which chocolate bars are wrapped. If its size is not enough, you can cut a larger blank from a roll of foil intended for baking products. To keep the foil on the surface, apply a thin layer of sealant. Then we press and level the foil over it. If she frowns, it's not a problem. The main thing is that there are no swellings, and she repeats the shape of the base.
We press the foil with our fingers and, smoothing out the bumps, form the most even surface. We trim the foil along the edges with scissors flush with the plastic base. Along the contour of the neck, we make a cutout with a knife for the LED, which will subsequently be installed in this place on the panel.
We make it from the bottom of the bottle cap, cutting off the threaded edges with a sharp knife and, if necessary, trimming them with scissors. Then, having made two holes in the socket with an awl or the tip of a knife, we pass the legs of the LED through them, pressing its base to it. For the correct installation of the LED lamp in the center of the cover, it is necessary to correctly select the distance between the holes according to the location of the legs at the base of the LED.
We bend the LED leads to the sides until they stop against the edges of the panel. We twist the conductors to them. If the twist turns out to be unreliable due to the properties of the wire cores or for other reasons, soldering is used. The conclusions after attaching the wires are bent along the panel. It is recommended to check the performance of the received part with the batteries used in the flashlight.
Then we cut out a contact pad for the battery from the tin sheet, which rests against the socket with the LED. By twisting or soldering we connect the pad - the terminal with a shorter wire. We attach the terminal to the spring, which in turn we attach to the socket. We use sealant to fasten the elements.
Then we glue the socket with the LED into the reflector.
Bottom and battery case
The part of the flashlight housing opposite to the reflector is also made from a part of a bottle with a neck. But only from the very neck with a lid. A terminal made of tin sheet is glued to its inner wall. A wire is also attached to it. This wire and the second wire from the LED will be used to control the flashlight. The terminal contacts the battery, being pressed by a cover that is screwed onto the neck.
The two main parts are ready. Now we need to make a battery case. To do this, we use dried and therefore no longer needed felt-tip pens. We leave only the body from them, which we shorten in length and cut along the ends along the axis, making two protrusions for gluing. Before cutting, make marks with a marker, applying the body of the felt-tip pen to the parts to be glued.
We apply glue to the protrusions and glue them, respectively, to the reflector and the back.
Then we cut out the details of the switch from the tin sheet. We mount the wires to them and glue the parts to the body.
We insert batteries into the flashlight and use it. This, of course, is not a factory-made flashlight with a high-quality reflector and high beam. But on the other hand, it is handmade, it is your own product, which gives good close-range lighting and gives great pleasure, and money cannot buy it. Now you have a visual representation of how easily you can make a lantern yourself.
Ready flashlight and light from it
As a rule, from electric lamps it is desirable to obtain the maximum brightness of the glow. However, sometimes lighting is required that will minimally disrupt vision adaptation to darkness. As you know, the human eye can change its photosensitivity over a fairly wide range. This allows, on the one hand, to see at dusk and in poor light, and on the other hand, not to go blind on a bright sunny day. If at night you go out of a well-lit room into the street, then for the first moments almost nothing will be visible, but gradually your eyes will adapt to new conditions. Full adaptation of vision to the dark takes about one hour, after which the eye reaches its maximum sensitivity, which is 200 thousand times higher than daylight. In such conditions, even short-term exposure to bright light (turning on a flashlight, car headlights) greatly reduces the sensitivity of the eyes. However, even with full adaptation to the dark, it may be necessary, for example, to read a map, illuminate the scale of the device, and the like, and this requires artificial lighting. Therefore, lovers of astronomy, as well as anyone who needs to consider something in poor lighting conditions, do not need a bright flashlight.
In the manufacture of an astronomical lantern, one should not strive for excessive miniaturization. The body of an astronomical flashlight should be light and large enough so that in poor lighting conditions it can be easily found (otherwise you will drop it under your feet and look for a flashlight for half an hour). A road soap dish was used as a case. Switches should be such that they can be easily operated by touch and with gloves.
The eye is maximally sensitive to light from a long wavelength of 550 nm (green light), and in the dark, the maximum sensitivity of the eye shifts towards short wavelengths up to 510 nm (effect Purkinje). Therefore, it is preferable to use red LEDs in an astronomical lantern, and not blue, or even more so green. To red light, the sensitivity of the eyes is less, which means that red lighting will less disrupt adaptation to the dark.
In addition to the main lantern, you can make several simple beacons to illuminate various objects. The fact is that few astronomy lovers can afford to have a full-fledged amateur observatory. Most are watching from the balcony. And in a tight space, and even in the dark, you can easily catch your foot and fill up the tripod of a telescope or camera. In addition, suddenly meet in the dark knee with the corner of a drawer or bedside table, the same pleasure is small. Therefore, it is advisable to use the simplest mini flashlights to illuminate tripod legs, sharp corners of furniture, shelves with accessories, and so on. In principle, just an LED fixed with adhesive tape on a 3 V battery of the type 2032 or similar. But, firstly, without a current-limiting resistor, the LED glow is too bright, and secondly, it is desirable to have a switch even in the simplest flashlight. Guided by these considerations, several such beacons were made.
A reed switch paired with a magnet is used as a switch. The 3 V battery mount is self-made. A current-limiting resistor is switched on in series with the LED, its value must be selected so that in the dark, with a direct look at the LED lens, the light does not blind the eyes even at close range. In different beacons, you can use LEDs of different colors to facilitate identification, while remembering that the eye does not have the same sensitivity to light with different wavelengths. You can use flashing LEDs.
In addition, a couple more designs of simple LED lights. The structures specifically described below were not intended for astronomical purposes, but they can easily be adapted for such use.
A simple waterproof flashlight can be made from a film can. We will need: a new jar of film, a 3 V LED, 2-3 reed switches, a 3 V lithium battery 2032 , cotton wool (case filler), a block for a battery from an old flashlight. To ensure water resistance, it is necessary that there are no holes in the body of the flashlight. So as a switch, you can use sealed contacts. For reliable operation, it is better to take 2-3 reed switches, since when turning along the longitudinal axis, the sensitivity of the reed switch changes. So, we collect a flashlight according to the scheme.
We bend the wires so that everything fits in the case, I filled the empty space with cotton so that nothing dangles. We place the circuit in the case. It is important that the film jar is new, i.e. so that the lid closes as tightly as possible. Any magnet will work as a switch. The flashlight of this design continued to work after 10 hours in the water. The cotton wool remained dry. So, long-term lying in a puddle will not damage such a device.
Surely radio amateurs have pads from failed 9 V batteries of the Krona type. On the basis of such a block, you can assemble a simple flashlight that does not actually need a body. An LED is connected to the contacts of the block through a current-limiting resistor.
Outside, the LED and resistor are wrapped with several layers of insulating tape. In the position put on the battery, the flashlight forms a single unit with it.
Thus, it is possible to adapt almost any suitable case and battery for a homemade flashlight, although below 3.5 V you will already need to install LEDs. Thank you for your attention. Author Denev.
Discuss the article LED FLASHLIGHTS WITH YOUR HANDS
