We present to your attention probably the simplest, but most interesting LED flasher circuit. If you have a small Christmas tree made of shiny rain, then a bright 5-7 cd LED mounted in its base that not only lights up, but also blinks is a very simple and beautiful decoration for your workplace. The power supply of the circuit is 3-12 V, can be replaced by power from the USB port. The previous article was also about an LED flasher, but unlike it, this article will talk about a single LED flasher, which in no way narrows its scope, I would say even the opposite. Surely you have seen a winking green, red or blue light more than once, for example, in car alarm. Now you have the opportunity to assemble a simple LED flasher circuit. Below is a table with the parameters of the parts in the circuit for determining the flash frequency.
In addition to this application, you can use the LED flasher as a car alarm emulator. Installing a new car alarm is not a simple and troublesome task, but having the specified parts on hand can be quickly assembled LED flasher circuit and now your car is “protected” for the first time. At least from accidental hacking. Such a “car alarm” - an LED flashing in the crack of the dashboard will scare off inexperienced burglars, because this is the first sign of a working alarm? You never know where else you will need a flashing LED.
The frequency with which the LED lights up depends on the resistance of resistors R1 and R2 and the capacitance of capacitor C1. At the time of debugging, instead of resistors R1 and R2, you can use variable resistors of the corresponding ratings. To slightly simplify the selection of elements, the table below shows the ratings of the parts and the corresponding flash frequency.
If a flasher on an LED refuses to work at certain values, you must first of all pay attention to resistor R1, its resistance may be too low, and also to resistor R2, its resistance may be too high. The duration of the pulses themselves depends on resistor R2, and the duration of the pause between pulses depends on resistor R1.
The LED flasher circuit with minor modifications can become sound pulse generator. To do this, you will need to install a speaker with a resistance of up to 4 ohms in place of resistor R3. Replace LED HL1 with a jumper. Use a transistor of sufficient power as transistor VT2. In addition, it is necessary to select capacitor C1 of the required capacity. The choice is made as follows. Let's say we have elements with parameters from row 2 of the table. Pulse frequency 1Hz (60 pulses per minute). And we want to get sound with a frequency of 1000Hz. Therefore, it is necessary to reduce the capacitance of the capacitor by 1000 times. We get 10 µF / 1000 = 0.01 µF = 10 nF. In addition, you can play with decreasing the resistance of the resistors, but don’t get too carried away, you can burn the transistors.
One of our regular readers, especially for our site, suggested another option for a very simple LED flasher. Watch the video:
Let me tell you right away that the idea is not mine, it was taken from the website chipdip.ru. This is a simple flasher with 6 LEDs, the peculiarity of which is the complete absence of additional active control elements (transistors, microcircuits).
The basis of the device is a flashing red LED HL3 in series, with which two ordinary red LEDs HL1 and HL2 are connected. When the blinking LED HL3 lights up, the LEDs HL1 and HL2 light up along with it.
In this case, diode VD1 opens, which bypasses the green LEDs HL4-HL6, which then go out.
When the flashing LED HL3 goes out, the LEDs HL1 and HL2 go out along with it, and the group of green LEDs HL4-HL6 lights up.
Then the whole cycle repeats. You can see more details about the flasher in this video:
The device is powered by a 9 V Krona battery. Resistors are MLT-0.125, R1 100 Ohm, R2 300 Ohm. The original source used a VD1 diode of the KD522 type, it was replaced by a D220. LEDs can be anything with a voltage of 2.5-3 V and a current of 10-30 mA. Sincerely, Lekomtsev D. G.
Hello everyone, today we will look at a flasher using a single transistor. You can say these are the first steps in radio electronics, because the first thing I decided to assemble was a transistor flasher. The circuit is very simple and consists of four parts: an n-p-n conductivity transistor (if you don’t know, search on Google, read what kind of thing it is) in my case it was bc547, an electrolytic capacitor of 470 uF (microfarads), a 1.8 kilo-ohm resistor and a green LED .
It is not so easy to assemble - you need to know where the plus and minus are at the LED and capacitor. The polarity of the LED is checked by connecting it to a 5-10 volt power source through a 100 Ohm resistor.
The capacitor is simpler, since on the body there is a white, yellow, blue line - on that side it has a minus, and on the other side it has a plus.
It’s better to look up the pinout of the transistor you are using on the Internet, in my case it’s like this:
We learned something about radio components, now let’s look at the circuit. There is nothing complicated about it. Let's start soldering. We clean the soldering iron tip from dirt and oxide.
Now let's look at the parts that I desoldered from the boards. To identify the resistance value, use .
Then we solder the capacitor, carefully look at the pinout of the transistor and the polarity of the LED and capacitor. The resistor has no polarity - it can be soldered on either side.
Our device is assembled. We solder the wiring and test it, the operating voltage is 8-18 volts.
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This circuit can be used to indicate an alarm. The homemade product is connected to a stabilized power source with a voltage of 12 V. Such a source can be a power supply with an adjustable output voltage, purchased on the radio market. The power supply is called stabilized because it contains a stabilizer that keeps the output voltage at a certain level.
The circuit is as simple as possible, it contains only 4 parts: a transistor KT315 of the p-p-n structure, a 1.5 kOhm resistor, an electrolytic capacitor of 470 μF and a voltage of at least 16 V (the capacitor voltage should always be an order of magnitude greater than the homemade supply voltage) and LED (in our case, red). To connect the parts correctly, you need to know their pinout (pinout). The pinout of the transistor and LED of this design is shown in Fig. 5.2. Transistors of the KT315 series are the same in appearance as KT361. The only difference is the placement of the letter. For the former, the letter is placed on the side, for the latter - in the middle.
Now, using a soldering iron and wires, let's try to assemble our device. In Fig. Figure 5.3 shows how you should connect the parts together. Blue lines are wires, thick black dots are solder points. This type of installation is called wall-mounted; there is also mounting on printed circuit boards.
Rice. 5.2. - Pinout:
a) transistor KT315B
b) LED AL307B
Rice. 5.3. - Appearance of the assembled device
Check that the parts are connected correctly and connect the device to the power supply. A miracle happened - the LED began to flash brightly. Your first homemade product has worked!!!
If you don’t have the opportunity to buy a ready-made flashing LED, where the necessary elements are built into the bulb to perform the desired function (all you have to do is connect the battery), try assembling your own circuit. You will need little: calculate the LED resistor, which together with the capacitor sets the oscillation period in the circuit, limit the current, select the type of switch. For some reason, the country's economy is driven by the mining industry; electronics are buried deep in the ground. I'm tense with the element base.
When connecting an LED, learn a minimum of theory - the VashTechnic portal is ready to help. The region of the pn junction, due to the existence of hole and electronic conductivity, forms a zone of energy levels unusual for the thickness of the main crystal. By recombining, charge carriers release energy; if the value is equal to a quantum of light, the junction of the two materials begins to radiate. The hue is determined by certain quantities, the relationship looks like this:
E = h c / λ; h = 6.6 x 10-34 is Planck’s constant, c = 3 x 108 is the speed of light, the Greek letter lambda denotes wavelength (m).
From the statement it follows: a diode can be created where the difference in energy levels is present. This is how LEDs are made. Depending on the difference in levels, the color is blue, red, green. Rare LEDs have the same efficiency. The blue ones, which historically appeared last, are considered weak. The efficiency of LEDs is relatively low (for semiconductor technology), rarely reaching 45%. The specific conversion of electrical energy into useful light energy is simply amazing. Each W of energy produces 6-7 times more photons than an incandescent filament under equivalent consumption conditions. Explains why LEDs have a strong position in lighting technology today.
Creating a flasher based on semiconductor elements is incomparably simpler. Relatively low voltages are enough, the circuit will start working. The rest comes down to the correct selection of key and passive elements to create a sawtooth or pulse voltage of the desired configuration:
Obviously, connecting an LED to a 230 volt network seems like a bad idea. There are similar circuits, but it is difficult to make it blink, the element base is missing. LEDs operate from much lower supply voltages. The most accessible are:
The design of the LED is clear, the combustion conditions are known, let's start implementing the idea. Let's make the element blink.
A computer power supply is an ideal option for testing SMD0603 LEDs. You just need to install a resistive divider. According to the technical documentation diagram, the resistance of p-n junctions in the forward direction is assessed, with the help of a tester. Direct measurement is not possible here. Let's put together the diagram shown below:
The +3.3 V wire of the computer power supply is orange insulated, we take the circuit ground from the black one. Please note: it is dangerous to turn on the module without load. Ideal to connect a DVD drive or other device. If you have the ability to handle live devices, it is permissible to remove the side cover, remove the necessary contacts from there, and do not remove the power supply. The connection of LEDs is illustrated by the diagram. Have you measured the resistance on the parallel connection of LEDs and stopped?
Let us explain: in working condition, you will need to turn on several LEDs; let’s do a similar setup. The supply voltage on the chip will be 2.5 volts. Please note that the LEDs are flashing and the readings are inaccurate. The maximum does not exceed 2.5 volts. Indication of successful operation of the circuit is expressed by blinking LEDs. To make the part flicker, remove the power from unnecessary ones. It is possible to assemble a debugging circuit with three variable resistors - one in a branch of each color.
You need to take significant values, and don’t forget: we will significantly limit the current flowing through the LEDs. In fact, you will need to think through the question according to the situation.
Flashing LED circuit
The circuit shown in the figure uses avalanche breakdown of the transistor to operate. KT315B, used as a key, has a maximum reverse voltage between the collector and base of 20 volts. There is little danger in such inclusion. For the KT315Zh modification, the parameter is 15 volts, much closer to the selected supply voltage of +12 volts. A transistor should not be used.
Avalanche breakdown abnormal mode of p-n junction. Due to the excess of the reverse voltage between the collector and the base, atoms are ionized by impacts of accelerated charge carriers. A mass of free charged particles is formed, carried away by the field. Eyewitnesses claim: for the breakdown of the KT315 transistor, a reverse voltage applied between the collector and emitter with an amplitude of 8-9 V is required.
A few words about the operation of the circuit. At the initial moment of time, the capacitor begins to charge. Connected to +12 volts, the rest of the circuit is broken - the transistor switch is closed. Gradually, the potential difference increases and reaches the avalanche breakdown voltage of the transistor. The capacitor voltage drops sharply, two open p-n junctions are connected in parallel:
In total, the voltage will be about 1 volt, the capacitor begins to discharge through the open p-n junctions, only the voltage drops below 7-8 volts, and your luck runs out. The transistor switch is closed, the process is repeated again. The circuit is inherent in hysteresis. The transistor opens at a higher voltage than it closes. Due to the inertia of processes. We see how the LED works.
The values of the resistor and capacitance determine the oscillation period. The capacitor can be taken much smaller by connecting a small resistance between the transistor collector and the LED. For example, 50 Ohm. The discharge constant will increase sharply, and it will be easier to check the LED visually (the burning time will increase). It is clear that the current should not be too large; the maximum values are taken from reference books. It is not recommended to connect LED lamps due to the low thermal stability of the system and the presence of abnormal transistor mode. We hope the review turned out to be interesting, the pictures are intelligible, and the explanations are clear.
