The master reveals the secret of a simple LED flasher with sound, built with his own hands using electronics from a broken electronic-mechanical watch.
To operate, you need a mechanism from an electronic-mechanical clock with a ticking motion. A broken mechanism will also work, since the malfunction is 99% due to damage to the mechanics. Please note that a smooth-running mechanism is not suitable for crafts. It is easy to distinguish the mechanisms; if you look carefully at the photographs, 3 large gears are clearly visible under the body of the ticking clock, but under the body of the smooth running mechanism there are four gears. The process of removing the electronics board is clearly shown in the video. Next, work with the circuit must be carried out according to the following instructions:
1. We remove all the mechanics with our own hands and put them aside. The wires from the coil can be broken.
2. Mark the polarity of the power terminals on the board. Carefully pry up the electronics board and remove it.
Ticking mechanism
3. Tin the contact pads with solder. This must be done quickly and carefully. When overheated, the pads easily peel off and then break off.
4. Solder the power conductors. The clock chip will operate when supplied with a voltage of 1.5 to 5 Volts.
5. Solder a TR1203 type sound emitter and any LED to the board, depending on what purposes you want to use the resulting circuit. Watch the video and photo of the flasher circuit. The flasher will work and should blink the LED every second, and then beep. This is perhaps what distinguishes the circuit from all similar flashing lights. You can connect two LEDs to the circuit and they will flash sequentially and alternately, why not a ready-made controller for flying models of replica airplanes?
There is a strong need to make the LED blink to enhance attracting a person’s attention to the signal. But to make a complex circuit there is simply no time and space to place radio elements. I'll show you a circuit consisting of just three that will make the LED blink.
The circuit works well on 12 volts, which should be of interest to motorists. If we take the full range of the supply voltage, then it lies in the range of 9-20 volts. So this device can find a lot of applications.
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:
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.
Flashing LEDs are often used in various signal circuits. Light emitting diodes (LEDs) of various colors have been on sale for quite a long time, which blink periodically when connected to a power source. No additional parts are needed to make them blink. A miniature integrated circuit that controls its operation is mounted inside such an LED. However, for a novice radio amateur it is much more interesting to make a flashing LED with your own hands, and at the same time study the principle of operation of an electronic circuit, in particular flashers, and master the skills of working with a soldering iron.
There are many schemes that can be used to make an LED blink. Flashing devices can be made either from individual radio components or based on various microcircuits. First, we will look at the multivibrator flasher circuit using two transistors. The most common parts are suitable for its assembly. They can be purchased at a radio parts store or “obtained” from obsolete televisions, radios and other radio equipment. Also in many online stores you can buy kits of parts for assembling similar circuits of LED flashers.
The figure shows a multivibrator flasher circuit consisting of only nine parts. To assemble it you will need:
It is not necessary that paired parts, for example resistors R2 and R3, have the same value. A small spread in values has virtually no effect on the operation of the multivibrator. Also, this LED flasher circuit is not critical to the supply voltage. It works confidently in the voltage range from 3 to 12 volts.
The multivibrator flasher circuit works as follows. At the moment of supplying power to the circuit, one of the transistors will always be open a little more than the other. The reason could be, for example, a slightly higher current transfer coefficient. Let transistor T2 initially open more. Then the charging current of capacitor C1 will flow through its base and resistor R1. Transistor T2 will be in the open state and its collector current will flow through R4. There will be a low voltage on the positive plate of capacitor C2, connected to the collector T2, and it will not charge. As C1 charges, the base current T2 will decrease and the collector voltage will increase. At some point, this voltage will become such that the charging current of capacitor C2 will flow and transistor T3 will begin to open. C1 will begin to discharge through transistor T3 and resistor R2. The voltage drop across R2 will reliably close T2. At this time, current will flow through the open transistor T3 and resistor R1 and LED1 will light up. In the future, charge-discharge cycles of capacitors will be repeated alternately.
If you look at the oscillograms on the collectors of the transistors, they will look like rectangular pulses.
When the width (duration) of rectangular pulses is equal to the distance between them, then the signal is said to have a meander shape. By taking oscillograms from the collectors of both transistors at the same time, you can see that they are always in antiphase. The duration of the pulses and the time between their repetitions directly depend on the products R2C2 and R3C1. By changing the ratio of products, you can change the duration and frequency of LED flashes.
To assemble the blinking LED circuit, you will need a soldering iron, solder and flux. As a flux, you can use rosin or liquid soldering flux, sold in stores. Before assembling the structure, it is necessary to thoroughly clean and tin the terminals of the radio components. The terminals of the transistors and the LED must be connected in accordance with their purpose. It is also necessary to observe the polarity of connection of electrolytic capacitors. The markings and pin assignments of KT315 transistors are shown in the photo.
Most LEDs operate at voltages above 1.5 volts. Therefore, they cannot be lit in a simple way from one AA battery. However, there are LED flasher circuits that allow you to overcome this difficulty. One of these is shown below.
In the LED flasher circuit there are two chains of capacitor charging: R1C1R2 and R3C2R2. The charging time of capacitor C1 is much longer than the charging time of capacitor C2. After charging C1, both transistors open and capacitor C2 is connected in series with the battery. Through transistor T2, the total voltage of the battery and capacitor is applied to the LED. The LED lights up. After the discharge of capacitors C1 and C2, the transistors close and a new cycle of charging the capacitors begins. This LED flasher circuit is called a voltage boost circuit.
We looked at several LED flashing light circuits. By assembling these and other devices, you can not only learn how to solder and read electronic circuits. As a result, you can get fully functional devices useful in everyday life. The matter is limited only by the imagination of the creator. With some ingenuity, you can, for example, make an LED flasher into a refrigerator door open alarm or a bicycle turn signal. Make the eyes of a soft toy blink.
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