Electrical diagram of a flashing light on a car. How to make a flashing LED. How the device works
Hello again everyone! In this article I will tell novice radio amateurs about how to make a simple flasher with just one cheapest transistor. Of course, you can find ready-made ones on sale, but they are not available in all cities, the frequency of their flashes is not regulated, and the supply voltage is quite limited. It is often easier not to go shopping and not wait for weeks for an order from the Internet (when you need to have a flashing light here and now), but to assemble it in a couple of minutes using the simplest scheme. To make the structure we will need:1 . Transistor type KT315 (It doesn’t matter whether it has the letters b, c, d - any will do).
2 . Electrolytic capacitor voltage of at least 16 volts, and a capacity of 1000 microfarads - 3000 microfarads (The lower the capacity, the faster the LED flashes).
3 . Resistor 1 kOhm, set the power as you like.
4 . Light-emitting diode(Any color except white).
5
. Two wires(Preferably stranded).
First, the LED flasher circuit itself. Now let's start making it. It can be done as an option on a printed circuit board, or it can also be mounted, it looks something like this:
We solder the transistor, then the electrolytic capacitor, in my case it is 2200 microfarads. Don't forget that electrolytes have polarity.
LED beacon circuit on timer KR1006VI1 |
This design, or rather its diagram, can be called simple and accessible. The device operates on the basis of the KR1006VI1 timer, which has two precision comparators. In addition, the device includes a timing oxide capacitor C1, a voltage divider across resistances R1 and R2. From the third output of the DA1 chip, control pulses follow to the LEDs HL1-HL3.
The circuit is turned on using toggle switch SB1. At the initial moment of time, the output of the timer has a high voltage level and the LEDs light up. Capacity C1 begins to charge through the circuit R1 R2. After one second, the time can be adjusted by resistances R1 R2 and capacitor C1, the voltage on the capacitor plates reaches the response value of one of the comparators. In this case, the voltage at pin three DA1 will be zero, the LEDs will go out. This continues from cycle to cycle as long as voltage is applied to the amateur radio structure.
It is recommended to use high-power LEDs HPWS-T400 or similar ones with a current consumption of no higher than 80 mA in the design. You can also use one LED, for example LXHL-DL-01, LXHL-FL1C, LXYL-PL-01, LXHL-ML1D, LXHL-PH01.
Finding various objects or, for example, pets in the dark will become easier if you attach our amateur radio development to them, which will automatically turn on when darkness falls and begin to emit a light signal.
This is a regular asymmetrical multivibrator based on bipolar transistors of different conductivity VT2, VT3, which generates short pulses with an interval of a couple of seconds. The light source is a powerful LED HL1, the light sensor is a phototransistor.
A phototransistor with resistances R1, R2 forms a voltage divider in the base circuit of transistor VT2. During daylight hours, the voltage at the emitter junction of transistor VT2 is low, and it is locked together with its colleague VT3. With the onset of darkness, the transistors begin to operate in the mode of generating pulses from which the LED flashes
It is recommended to start discovering the world of radio electronics, full of mysteries, without specialized education, by assembling simple electronic circuits. The level of satisfaction will be higher if the positive result is accompanied by a pleasant visual effect. The ideal option is circuits with one or two flashing LEDs in the load. Below is information that will help in implementing the simplest DIY schemes.
Ready-made flashing LEDs and circuits using them
Among the variety of ready-made flashing LEDs, the most common are products in a 5 mm housing. In addition to ready-made single-color flashing LEDs, there are two-terminal versions with two or three crystals of different colors. They have a built-in generator in the same housing with the crystals, which operates at a certain frequency. It issues single alternating pulses to each crystal according to a given program. The blinking speed (frequency) depends on the set program. When two crystals glow simultaneously, the flashing LED produces an intermediate color. The second most popular are flashing light-emitting diodes controlled by current (potential level). That is, to make a LED of this type blink, you need to change the power supply at the corresponding pins. For example, the emission color of a two-color red-green LED with two terminals depends on the direction of current flow.
A three-color (RGB) four-pin flashing LED has a common anode (cathode) and three pins for controlling each color separately. The flashing effect is achieved by connecting to an appropriate control system.
It’s quite easy to make a flasher based on a ready-made flashing LED. To do this, you will need a CR2032 or CR2025 battery and a 150–240 Ohm resistor, which should be soldered to any pin. Observing the polarity of the LED, the contacts are connected to the battery. The LED flasher is ready, you can enjoy the visual effect. If you use a Krona battery, based on Ohm's law, you should select a resistor of higher resistance.
Conventional LEDs and flasher systems based on them
A novice radio amateur can assemble a flasher using a simple one-color light-emitting diode, having a minimum set of radio elements. To do this, we will consider several practical schemes, characterized by a minimum set of radio components used, simplicity, durability and reliability. 
The first circuit consists of a low-power transistor Q1 (KT315, KT3102 or a similar imported analogue), a 16V polar capacitor C1 with a capacity of 470 μF, a resistor R1 of 820-1000 ohms and an LED L1 like AL307. The entire circuit is powered by a 12V voltage source.
The above circuit works on the principle of avalanche breakdown, so the base of the transistor remains “hanging in the air”, and a positive potential is applied to the emitter. When turned on, the capacitor is charged to approximately 10V, after which the transistor opens for a moment and releases the accumulated energy to the load, which manifests itself in the form of LED blinking. The disadvantage of the circuit is the need for a 12V voltage source.
The second circuit is assembled on the principle of a transistor multivibrator and is considered more reliable. To implement it you will need:
- two KT3102 transistors (or their equivalent);
- two 16V polar capacitors with a capacity of 10 µF;
- two resistors (R1 and R4) of 300 Ohms each to limit the load current;
- two resistors (R2 and R3) of 27 kOhm each to set the base current of the transistor;
- two LEDs of any color.
In this case, a constant voltage of 5V is supplied to the elements. The circuit operates on the principle of alternate charge-discharge of capacitors C1 and C2, which leads to the opening of the corresponding transistor. While VT1 discharges the accumulated energy of C1 through the open collector-emitter junction, the first LED lights up. At this time, a smooth charge of C2 occurs, which helps to reduce the base current VT1. At a certain moment, VT1 closes, and VT2 opens and the second LED lights up.
The second scheme has several advantages:
- It can operate in a wide voltage range starting from 3V. When applying more than 5V to the input, you will have to recalculate the resistor values so as not to break through the LED and not exceed the maximum base current of the transistor.
- You can connect 2–3 LEDs to the load in parallel or in series by recalculating the resistor values.
- An equal increase in the capacitance of the capacitors leads to an increase in the duration of the glow.
- By changing the capacitance of one capacitor, we get an asymmetrical multivibrator in which the glow time will be different.
In both options, you can use pnp transistors, but with correction of the connection diagram.
Sometimes, instead of flashing LEDs, a radio amateur observes a normal glow, that is, both transistors are partially open. In this case, you need to either replace the transistors or solder resistors R2 and R3 with a lower value, thereby increasing the base current.
It should be remembered that 3V power will not be enough to light an LED with a high forward voltage value. For example, a white, blue or green LED will require more voltage.
In addition to the considered circuit diagrams, there are a great many other simple solutions that cause the LED to blink. Beginning radio amateurs should pay attention to the inexpensive and widespread NE555 microcircuit, which can also implement this effect. Its versatility will help you assemble other interesting circuits.
Application area
Flashing LEDs with a built-in generator have found application in the construction of New Year's garlands. By assembling them in a series circuit and installing resistors with slight differences in value, they achieve a shift in the blinking of each individual element of the circuit. The result is an excellent lighting effect that does not require a complex control unit. It is enough just to connect the garland through a diode bridge.
Flashing light-emitting diodes, controlled by current, are used as indicators in electronic technology, when each color corresponds to a certain state (on/off charge level, etc.). They are also used to assemble electronic displays, advertising signs, children's toys and other products in which multi-colored flashing arouses people's interest.
The ability to assemble simple flashing lights will become an incentive to build circuits using more powerful transistors. With a little effort, you can use flashing LEDs to create many interesting effects, such as a traveling wave.
Read also
There are situations when you need a beacon circuit that would create really bright and noticeable flashes, for example, on a company car or a camping lantern.
Above is a diagram of such a beacon that flashes, creating a strobe effect.
The circuit is powered from a power source of at least 10 volts. To reduce the operating voltage, you can replace transistors VT1 and VT2 with transistors with the lowest voltage FE transition. And also by adjusting the values of resistors R1 and R2.
Resistors R3 and R4 regulate flashes; if you increase the resistor values to 100 Ohms, the LEDs will light up smoothly. Thanks to 1 Ohm resistors, the LEDs flash quickly, which creates a strobe effect.
Capacitors C1 and C2 regulate the flash frequency of LEDs VD1 and VD2. By reducing the capacitance of the capacitors you can increase the flash speed.
It is advisable to install brighter LEDs with greater luminous intensity.
As can be seen from the diagram, the device consists of two similar blocks, the first block consists of resistors R1 and R3, capacitor C1, transistor VT1 and LED VD1. The remaining details belong to the second block. By composing additional blocks you can increase the number of beacons.
Pay attention to the bases of transistors VT1 and VT2, they are not connected, this is not an error, and indeed the bases of the transistors in the device are not connected!
The device was mounted on a printed circuit board, the board was inserted into the relay housing, then it was tested and installed on a Niva company car in place of the standard dimensions, three LEDs were installed in each headlight. The device has been operating successfully for the second year, the components do not heat up, and no malfunctions have been recorded.
The device was developed more than a year ago, at the request of a friend, based on data taken on the Internet from open sources.
List of radioelements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| VT1, VT2 | Bipolar transistor | KT315B | 2 | With any letter index | To notepad | |
| C1, C2 | Electrolytic capacitor | 1000 µF 16 V | 2 | To notepad | ||
| R1, R2 | Resistor | 1 kOhm | 2 | To notepad | ||
| R3, R4 | Resistor | 1 ohm | 2 | To notepad | ||
| VD1, VD2 | Light-emitting diode | 2 |
Various special vehicles are equipped with flashing lights, which are usually a lamp around which a reflective mirror rotates using an electric motor. In amateur conditions, the effect of rotating light in a beacon can be achieved in another way, if four lamps are placed in the beacon body, each of which has its own fixed reflector. Place the lamps diametrically opposite in the plane of the circle of the base of the beacon, so that they are directed in four different directions. And then, using an electronic device, switch these lamps in a circle.
The schematic diagram of such a device is shown in the figure. The beacon uses powerful automotive lamps of 40-60 W each. An attempt to switch these lamps using transistor switches on the KT829 did not give positive results - the transistors quickly failed. Therefore, three automotive electromagnetic relays with switching contacts were used as switching elements.
The relays are switched on by transistor switches VT1-VT3, which receive levels from the output of the binary counter D2 and the decoder on elements D1.3 and D1.4. The counter receives pulses from the multivibrator on D1.1 and D1.2.
Let's assume that in the initial state the counter is in the zero position. At the same time, its outputs are zero and all three relays are de-energized. In this case, the 12V voltage is supplied through contacts K1 and K2 to lamp H1. With the arrival of the first pulse, the counter moves to position P and a unit appears at its output 3. In this case, relay P1 is activated and a voltage of 12V is supplied to lamp H2 through K1 and K3.
Then the second pulse arrives at the counter. A one appears on pin 4, and a zero appears on pin 3. Relay P1 turns off and relay P2 is activated. Voltage through K1 and K2 is supplied to the NC lamp. With the arrival of the third pulse, units are set at both outputs of the counter and both relays are activated. In this case, units arrive at both inputs of element D1.3, and a unit appears at the output of D1.4. Thus, all three relays are activated at once. In this case, voltage is supplied to lamp H4 through contacts K1 and KZ.
Then the whole process is repeated. You can set the speed of rotation of the light by selecting the value of R1. If instead you install a series-connected constant resistor of 100-200 kOhm and a variable resistor of 500-1000 kOhm, you can adjust the speed during operation.
Electromagnetic relays type 112.3747-10E from the VAZ-2108 car (they have five contacts). Instead of the K561IE10 counter, you can use any CMOS binary counter, or assemble the counter using flip-flops of the K561TM2 microcircuit.