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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Modernization of a flashlight or circuitry of voltage converters. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Lighting Lyrical introduction This article will consider the modernization of a flashlight using the example of a device from the notorious Philips company. So what are its disadvantages? As with all flashlights, this device was noticed a significant decrease in the brightness of the glow of the incandescent lamp when the batteries were "planted". And of course, low efficiency and service life. And, nevertheless, the solution of these eternal problems exists. LEDs! But is it enough to replace only the light source? No. Most flashlights use the now classic circuit, in which two 1,5 volt batteries are connected in series. But a voltage of 3 volts is not enough for the LED to glow brightly, therefore, it is worth including a converter in the circuit. The converter has a more stable output current, when the input can be 0,5 V or less. What happens to a lamp lantern if its batteries are discharged to such a limit? That's right, it doesn't work. Therefore, the converter is the most successful move in solving this problem. A new problem arises: where to place it? After all, there is often no space in the lantern body. If you have open-frame components, you can mark them directly in the lamp base, but if not? This article will help you figure it out. On this, the lyrics can be considered finished. Let's move on to the circuitry. Circuitry As I said, there is a solution. Quite original, I think. Consider the converter circuit:
The diagram shows a blocking generator. Excitation is achieved by transformer coupling on transformer T1. The voltage pulses that occur in the right (according to the scheme) winding are added to the voltage of the power source and fed to the VD1 LED. Of course, it would be possible to exclude the capacitor and resistor in the base circuit of the transistor, but then VT1 and VD1 may fail when using branded batteries with low internal resistance. The resistor sets the operating mode of the transistor, and the capacitor passes the RF component. The circuit used a KT315 transistor (as the cheapest), an ultra-bright LED (as the brightest). Let's talk about the transformer separately. For its manufacture, a ferrite ring is required (approximate size 10x6x3 and a permeability of about 1000 HH). The wire diameter is about 0,2 mm. Two coils of 20 turns each are wound on the ring. If you do not have a ring, then you can use a cylinder similar in volume and material. You just have to wind 60-100 turns for each of the coils. An important point: you need to wind the coils in different directions. At worst, you can use a nail, but a large nail, and it takes about 150 turns for one coil. In addition, the efficiency of a nail is much lower than that of ferrite. Let's move on to practice now. Practice Consider a photo of a flashlight. This is necessary to understand the meaning of my research. There is nothing futuristic here, I will only note that the switch is located in the "fountain pen" button, and the gray cylinder is metal and conducts current.
So, step one. We create the "case" of the device.
We make a cylinder according to the size of the battery. For example, the size of the batteries in my flashlight is AAA. It can be made from paper (like me), or you can use a piece of any rigid tube. For gluing, we use "rubber" glue, as it is a good dielectric. We make holes along the edges of the cylinder, wrap it with a tinned conductor, and pass the ends of the wire into the holes. We fix both ends, but leave a piece of conductor at one of the ends: so that you can connect the converter to the spiral. (The nut shown in the picture is not needed yet)
Now let's assemble the converter itself. I did not have a ferrite ring (and it would not fit into a flashlight), so a cylinder of a similar material was used.
The cylinder was taken from an inductor from an old TV. The first coil is carefully wound on it. The threads are held together with glue. I got about 60 turns. Then the second, it is wound in the opposite direction. I got 60 or so again; I didn’t count exactly - I couldn’t wind it neatly. We fix the edges with glue. We dry. During the drying process, the coil can be slightly warmed up. I put it on a piece of paper on the ceiling of a table lamp. Let it dry. And we move on. We assemble the converter according to the scheme:
Everything is located as in the figure: a transistor, a capacitor, a resistor, etc. We assembled the passive and active elements, solder the spiral on the cylinder, the coil. The current in the coil windings must go in different directions! That is, if you wound all the windings in one direction, then swap the conclusions of one of them, otherwise generation will not occur. We rejoice, because we got the following:
We insert everything inward, and use nuts as side plugs and contacts. We solder the coil leads to one of the nuts, and the VT1 emitter to the other. Glue. we mark the conclusions: where we will have an output from the coils, we put "-", where the output from the transistor with the coil we put "+" (so that everything is like in a battery). All. You have got something similar to what is shown in the previous figure. Now you should make a "lamp diode". We take an ordinary base from a light bulb that has served its purpose, and ...
One moment: there should be a minus of the LED on the base. Otherwise, nothing will work. There was another solution to the problem. Of course, it is possible to create a converter module directly with an LED in one package. In this case, as you probably already noticed, only two contacts are needed. You can do that too. But in this solution, you can not easily change the LEDs. Why change? Very simple, because you can use an ultraviolet LED, and check the authenticity of banknotes and much more. In addition, I find that my way of solving the problem is more ergonomic and interesting. Assembly technique
As is clear from the figure, the converter is a "substitute" for the second battery. But unlike it, it has three points of contact: with the plus of the battery, with the plus of the LED, and the common body (through the spiral). However, its location in the battery compartment is specific: it must be in contact with the positive of the LED. Simply put, the assembly sequence in the picture cannot be changed. Otherwise, as you may have guessed, the device will not work. Upgraded lantern in operation
Such a flashlight is more economical, ergonomic and, due to the absence of a second battery, is light. And the main advantage! All details can be found in the trash! Author: radioxoma, Vitebsk; Publication: cxem.net
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