If you decide to convert your car to LED lighting, you will need at least an lm317 current stabilizer for LEDs. Assembling a basic stabilizer is not at all difficult, but in order to avoid disastrous mistakes even with such a simple task, a minimal educational program will not hurt. Many people not involved in radio electronics often confuse concepts such as current stabilizer and voltage stabilizer.
Voltage determines how quickly electrons move through a conductor. Many passionate fans of hard computer overclocking increase the voltage of the central processor core, making it start to function faster.
Current strength is the density of electron movement within an electrical conductor. This parameter is extremely important for radioelements operating on the principle of thermionic secondary emission, in particular, light sources. If the cross-sectional area of the conductor is not able to pass the flow of electrons, excess current begins to be released in the form of heat, causing significant overheating of the part.
To better understand the process, let’s analyze the plasma arc (electric ignition of gas stoves and boilers works on its basis). At very high voltages, the speed of free electrons is so high that they can easily “fly” the distance between the electrodes, forming a plasma bridge.
And this is an electric heater. When electrons pass through it, they transfer their energy to the heating element. The higher the current, the denser the flow of electrons, the more the thermoelement heats up.
Any radio-electronic component, be it a light bulb or a computer's central processor, requires for optimal operation a clearly limited number of electrons that flow through the conductors.
Since our article is about a stabilizer for LEDs, we’ll talk about them.
With all their advantages, LEDs have one drawback - high sensitivity to power parameters. Even moderate excess of force and voltage can lead to burnout of the light-emitting material and failure of the diode.
Nowadays it is very fashionable to remodel a car's lighting system for LED lighting. Their color temperature is much closer to natural light than that of xenon and incandescent lamps, which makes the driver much less tired on long trips.
However, this solution requires a special technical approach. The rated supply current of a car LED diode is 0.1-0.15 mA, and the starting battery current is hundreds of amperes. This is enough to burn out a lot of expensive lighting elements. To avoid this, use a 12 volt stabilizer for LEDs in cars.
The amperage in a vehicle network is constantly changing. For example, a car air conditioner “eats” up to 30 amperes; when it is turned off, the electrons “allocated” to its operation will no longer return back to the generator and battery, but will be redistributed among other electrical appliances. If an additional 300 mA does not play a role in an incandescent lamp rated at 1-3 A, then several such surges can be fatal for a diode with a supply current of 150 mA.
To guarantee long-term operation of automotive LEDs, a current stabilizer based on lm317 is used for high-power LEDs.
According to the method of limiting the current, there are two types of devices:
It works on the principle of a voltage divider. It releases a current of a given parameter, dissipating the excess in the form of heat. The operating principle of such a device can be compared to a watering can equipped with an additional drain hole.
Advantages
Disadvantage: due to heating, it is poorly adapted to work with heavy loads.
Like a vegetable cutter, it cuts the incoming current through a special cascade, giving out a strictly dosed amount.
Advantages
Flaws
Considering the low current in car LEDs, you can assemble a simple stabilizer for LEDs with your own hands. The most affordable and simple driver for LED lamps and strips is assembled on the lm317 chip.
The LM317 radio-electronic module is a microcircuit used in current and voltage stabilization systems.
Circuit of the simplest stabilizer The simplest 12-volt voltage stabilizer can be assembled using this circuit. Resistor R1 limits the output current, R2 limits the output voltage. The capacitors used in this circuit reduce voltage ripple and increase operating stability.
The needs of the motorist will be satisfied by the simplest stabilization mechanism, since the supply voltage in the car network is quite stable.
To make a stabilizer for diodes in a car you will need:
We assemble according to the above diagram
The power and resistance of the resistor are calculated based on the current strength of the power supply and the current required by the LEDs. For an automotive LED with a power of 150 mA, the resistor resistance should be 10-15 Ohms, and the calculated power should be 0.2-0.3 W.
How to assemble it yourself, watch the video:
The availability and simplicity of the driver design on the lm317 chip allows you to painlessly re-equip the electric lighting systems of any car.
Vin (input voltage): 3-40 Volts
Vout (output voltage): 1.25-37 Volts
Output current: up to 1.5 Amps
Maximum power dissipation: 20 Watt
Formula to calculate output (Vout) voltage: Vout = 1.25 * (1 + R2/R1)
*Resistance in Ohms
*Voltage values are obtained in Volts
This simple circuit allows you to rectify alternating voltage into direct voltage thanks to a diode bridge made of diodes VD1-VD4, and then use an accurate substring resistor of the SP-3 type to set the voltage you need within the limits of the integrated stabilizer chip.
I used old ones as rectifier diodes FR3002, which once upon a time fell out of an ancient computer from the year 1998. Despite their impressive size (DO-201AD housing), their characteristics (Ureverse: 100 Volts; Idirect: 3 Amps) are not impressive, but that’s enough for me. For them we even had to widen the holes in the board, their pins are too thick (1.3mm). If you slightly change the board in the layout, you can immediately solder a ready-made diode bridge.
A radiator to remove heat from the 317 chip is required; it’s even better to install a small fan. Also, at the junction of the TO-220 chip case substrate with the heatsink, drop a little thermal paste. The degree of heating will depend on how much power the chip dissipates, as well as on the load itself.
Microcircuit LM317T I did not install it directly on the board, but brought out three wires from it, with the help of which I connected this component with the others. This was done so that the legs would not become loose and, as a result, would not be broken, because this part will be attached to the heat dissipator.
To be able to use the full voltage of the microcircuit, that is, adjust from 1.25 and right up to 37 Volts, we set the substring resistor with a maximum resistance of 3432 kOhm (in the store the closest value is 3.3 kOhm). Recommended type of resistor R2: interlinear multi-turn (3296).
The LM317T stabilizer chip itself and others like it are produced by many, if not all, companies producing electronic components. Buy only from trusted sellers, because there are Chinese counterfeits, especially often the LM317HV microcircuit, which is designed for an input voltage of up to 57 Volts. You can identify a fake microcircuit by its iron backing; in a fake, it has a lot of scratches and an unpleasant gray color, as well as incorrect markings. It also needs to be said that the microcircuit has protection against short circuits and overheating, but don’t count on them too much.
Do not forget that this (LM317T) integrated stabilizer is capable of dissipating power with a radiator only up to 20 Watts. The advantages of this common microcircuit are its low price, limitation of internal short circuit current, internal thermal protection
The scarf can be drawn with high quality even with an ordinary parchment marker, and then etched in a solution of copper sulfate/ferric chloride...
Photo of the finished board.
Let's consider the simplest option for making an LED driver with your own hands with minimal time investment. To calculate the current stabilizer on LM317 for LEDs, we use a calculator, which needs to indicate the required current strength for LED diodes. First draw up a circuit for switching on the LEDs, taking into account the maximum power of the microcircuit and the unit. Look for a cooling system for the entire structure in advance.
To make a current stabilizer on LM317 with the ability to regulate, instead of a constant resistor, install a powerful variable resistance. The variable resistance rating can be calculated by specifying the control limits to the calculator. The resistance can be from 1 to 110 Ohms, this corresponds to the maximum and minimum. But I recommend that you refuse to adjust the Amperes in the load with variable resistance. It will be difficult to implement correctly and the heating will be too high.
The power of a constant resistor for heat dissipation should be with a reserve, calculated by the formula:
A transformer or switching voltage source with polar voltage can be used as a power supply. As a rectifier, it is better to use a classic diode bridge, after which a large capacitor is installed.
The current regulator does not operate on a linear principle, so it can get quite hot due to its low efficiency. Having a decent radiator is a must. If the heating control shows a low heating temperature, it can be reduced.
If the number of Amperes required is more than 1.5A, then a couple of elements must be added to the standard circuit. You can get up to 10A by installing a powerful KT825A transistor and a 10-ohm resistor.
This option is suitable for those who do not have an LM338 or LM350 on hand.
The 3A version of the current stabilizer is made on the KT818 transistor. The amperes in the load are regulated and calculated in all circuits the same way on a calculator.
If you really want to assemble it but don’t have a suitable power supply, then there are several options to solve this. Barter with a neighbor or connect the circuit to a 9V battery like Krona. The photo shows the entire circuit assembled with an LED.
If 1A is required for LEDs, then we indicate this in the calculator and get a result of 1.25 ohms. There is no resistor of exactly the same value, so we install a suitable one with a value in the direction of increasing Ohm. The second option is to use parallel and series connection of resistors. By correctly connecting several resistances we get the required number of Ohms.
Your LM317 current stabilizers will be similar to the products below.
And if you suffer from complete LED fanaticism, it will look like this.
I strongly recommend not to operate the LM317 at extreme conditions; Chinese microcircuits do not have a safety margin. Of course, there is built-in protection against short circuits and overheating, but don’t expect it to work every time.
As a result of an overload, not only the LM317 can burn out, but also what is connected to it, and this is a completely different kind of damage.
Main parameters of LM317:
If a load of 1A is not enough for you, then you can use more powerful models of stabilizers LM338 and LM350, 5A and 3A, respectively.
To improve heat transfer, the TO-3 case was enlarged, this is often found in Soviet transistors. But it is also available in a small TO-220 case, designed for lighter loads.
LM338 parameters:
Thanks to Chinese hard work, power supplies, current and voltage stabilizers can be bought in foreign online stores for 50-150 rubles. The adjustment is driven by a small variable resistance; at 2-3 Amps they do not require a radiator to cool the driver controller. You can order, for example, on the popular bazaar Aliexpress.com. The main drawback is the wait for 2-4 weeks, but the price is the lowest, you can buy half a kilo at once.
I often search on Avito in my city for a quick and inexpensive method. I and many others order stabilizers with a reserve, in case they turn out to be faulty. Then they sell the excess through advertisements, and you can always bargain.
If the circuit requires a stabilizer for some non-standard voltage, then an excellent solution is to use the popular integrated stabilizer LM317T with the following characteristics:
For the LM317T microcircuit, the minimum connection circuit assumes the presence of two resistors, the resistance values of which determine the output voltage, an input and output capacitor.
The stabilizer has two important parameters: the reference voltage (Vref) and the current flowing from the adjustment pin (Iadj).
The value of the reference voltage can vary from instance to instance from 1.2 to 1.3 V, and on average is 1.25 V. The reference voltage is the voltage that the stabilizer chip strives to maintain across resistor R1. Thus, if resistor R2 is closed, then the output of the circuit will be 1.25 V, and the greater the voltage drop across R2, the greater the output voltage will be. It turns out that 1.25 V on R1 adds up with the drop on R2 and forms the output voltage.
The first time I calculated the divider for the microcircuit using the formula from the LM317T datasheet, I was given a current of 1 mA, and then for a very long time I wondered why the voltage and real voltage were different. And since then I have been asking R1 and counting according to the formula:
R2=R1*((Uout/Uop)-1).
I test in real conditions and clarify the values of resistances R1 and R2.
Let's see what they should be for the widespread voltages of 5 and 12 V.
But I would advise using the LM317T in the case of standard voltages, only when you urgently need to do something on your knees, and a more suitable microcircuit like 7805 or 7812 is not at hand.
And here is the pinout location of the LM317T:
By the way, the domestic analogue of LM317 - KR142EN12A - has exactly the same connection circuit.
It’s easy to make an adjustable power supply on this microcircuit: replace the constant R2 with a variable one, add a network transformer and a diode bridge.
You can also make a soft start circuit on LM317: add a capacitor and a current amplifier on a bipolar pnp transistor.
The connection circuit for digital control of the output voltage is also not complicated. We calculate R2 for the maximum required voltage and add chains of a resistor and transistor in parallel. Turning on the transistor will add, in parallel to the conductivity of the main resistor, the conductivity of the additional one. And the output voltage will decrease.
The current stabilizer circuit is even simpler than the voltage stabilizer, since only one resistor is needed. Iout = Uop/R1.
For example, in this way we get a current stabilizer for LEDs from lm317t:
It’s easy to make a charger for 12 V batteries based on the stabilizer, that’s what the datasheet offers us. Rs can be used to set the current limit, while R1 and R2 determine the voltage limit.
If the circuit needs to stabilize voltages at currents of more than 1.5 A, then the LM317T can still be used, but in conjunction with a powerful bipolar transistor of the pnp structure.
If we need to build a bipolar adjustable voltage stabilizer, then an analogue of the LM317T will help us, but working in the negative arm of the stabilizer - LM337T.
But this chip also has limitations. It is not a low-dropout regulator; on the contrary, it only starts to work well when the difference between the output and output voltage exceeds 7 V.
If the current does not exceed 100mA, then it is better to use low-dropout ICs LP2950 and LP2951.
If the output current of 1.5 A is not enough, then you can use:
The manufacturers of these stabilizers, in addition to increasing the output current, promise a reduced control input current to 50 μA and improved accuracy of the reference voltage.
But the switching circuits are suitable for LM317.
Hello. I bring to your attention a review of the integrated linear adjustable voltage (or current) stabilizer LM317 at a price of 18 cents apiece. In a local store, such a stabilizer costs an order of magnitude more, which is why I was interested in this lot. I decided to check what was being sold at that price and it turned out that the stabilizer was quite high quality, but more on that below.
The review includes testing in voltage and current stabilizer mode, as well as checking overheat protection.
For those interested, please...
Testing:
Similar stabilizers are produced by many manufacturers, here.
The position of the legs is as follows: 
1 - adjustment;
2 - exit;
3 - entrance.
We assemble a simple voltage stabilizer according to the diagram from the manual: 
Here's what we managed to get with 3 positions of the variable resistor: 
The results, frankly speaking, are not very good. I wouldn't dare call it a stabilizer.
Next, I loaded the stabilizer with a 25 Ohm resistor and the picture completely changed: 
Next, I decided to check the dependence of the output voltage on the load current, for which I set the input voltage to 15V, set the output voltage to about 5V using a trimmer resistor, and loaded the output with a variable 100 Ohm wirewound resistor. Here's what happened: 
It was not possible to obtain a current of more than 0.8A, because The input voltage began to drop (the power supply is weak). As a result of this testing, the stabilizer with the radiator heated up to 65 degrees: 
To check the operation of the current stabilizer, the following circuit was assembled: 
Instead of a variable resistor, I used a constant one, here are the test results: 
Current stabilization is also good.
Well, how can there be a review without burning the hero? To do this, I reassembled the voltage stabilizer, applied 15V to the input, set the output to 5V, i.e. 10V dropped on the stabilizer, and loaded it at 0.8A, i.e. 8W of power was released on the stabilizer. The radiator was removed.
The result was demonstrated in the following video:
With that, let me take my leave, good luck!
The product was provided for writing a review by the store. The review was published in accordance with clause 18 of the Site Rules.
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