Illumination of the receiver scale with a power supply of 1.5 volts. Connecting LEDs from batteries

This circuit is another one of a series of popular converters for one battery powered LED at 1.5 volts.

Description of the operation of the converter for the LED from 1.5 volts

After connecting the power through the resistor R2, the transistor T1 opens. Further, the current flowing through the resistor R3 opens the transistor T2 and the current begins to flow through the inductor L1. The current of the inductor L1 is constantly growing and is determined by the voltage of the battery, the inductor itself, as well as the resistance value of the resistor R3.

When the current in the inductor reaches its maximum, it reverses its direction and, consequently, the voltage polarity also changes. At this moment, the transistor T1 closes through the capacitor C1, followed by the transistor T2. Current from the opposite polarity coil passes through the LED, which lights up. After a while, transistors T1 and T2 turn on and the cycle repeats again.

The converter is able to increase the voltage up to 10 volts, so that it can easily light even two or three diodes at full brightness. The current flowing through the LED can be regulated within certain limits by changing the resistance of the resistor R3.

The converter for the LED is assembled on a single-sided board

Availability and relatively low prices for super-bright light-emitting diodes (LED) allow them to be used in various amateur devices. Beginning radio amateurs who use LED for the first time in their designs often wonder how to connect an LED to a battery? After reading this material, the reader will learn how to light an LED from almost any battery, what LED connection schemes can be used in a particular case, how to calculate circuit elements.

What batteries can be connected to the LED?

In principle, you can simply light the LED from any battery. Electronic circuits developed by radio amateurs and professionals make it possible to successfully cope with this task. Another thing is how long the circuit will work continuously with a specific LED (LEDs) and a specific battery or batteries.

To estimate this time, you should know that one of the main characteristics of any battery, whether it is a chemical element or a battery, is its capacity. Battery capacity - C is expressed in ampere-hours. For example, the capacity of common AAA finger batteries, depending on the type and manufacturer, can be from 0.5 to 2.5 ampere-hours. In turn, light-emitting diodes are characterized by a working current, which can be tens and hundreds of milliamps. Thus, you can approximately calculate how long the battery lasts using the formula:

T= (C*U baht)/(U work led *I work led)

In this formula, the numerator is the work that the battery can do, and the denominator is the power consumed by the light emitting diode. The formula does not take into account the efficiency of a particular circuit and the fact that it is extremely problematic to fully use the entire battery capacity.

When designing battery-powered devices, they usually try to ensure that their current consumption does not exceed 10 - 30% of the battery capacity. Guided by this consideration and the above formula, you can estimate how many batteries of a given capacity are needed to power a particular LED.

How to connect from a 1.5V AA battery

Unfortunately, there is no easy way to power an LED with a single AA battery. The fact is that the operating voltage of light emitting diodes usually exceeds 1.5 V. For this value, this value lies in the range of 3.2 - 3.4V. Therefore, to power the LED from one battery, you will need to assemble a voltage converter. Below is a diagram of a simple voltage converter on two transistors, with which you can power 1 - 2 super-bright LEDs with a working current of 20 milliamps.

This converter is a blocking oscillator assembled on a transistor VT2, a transformer T1 and a resistor R1. The blocking generator generates voltage pulses that are several times higher than the voltage of the power source. Diode VD1 rectifies these pulses. Inductor L1, capacitors C2 and C3 are elements of the smoothing filter.

Transistor VT1, resistor R2 and zener diode VD2 are elements of a voltage regulator. When the voltage across capacitor C2 exceeds 3.3 V, the zener diode opens and a voltage drop is created across resistor R2. At the same time, the first transistor will open and lock VT2, the blocking generator will stop working. Thus, the output voltage of the converter is stabilized at the level of 3.3 V.

As VD1, it is better to use Schottky diodes, which have a low voltage drop in the open state.

Transformer T1 can be wound on a 2000NN grade ferrite ring. The diameter of the ring can be 7 - 15 mm. As a core, you can use rings from converters of energy-saving light bulbs, filter coils of computer power supplies, etc. The windings are made with enameled wire with a diameter of 0.3 mm, 25 turns each.

This scheme can be painlessly simplified by eliminating the stabilization elements. In principle, the circuit can do without a choke and one of the capacitors C2 or C3. Even a novice radio amateur can assemble a simplified circuit with his own hands.

The circuit is also good because it will work continuously until the power supply voltage drops to 0.8 V.

How to connect from a 3V battery

You can connect a super-bright LED to a 3V battery without using any additional parts. Since the operating voltage of the LED is slightly more than 3 V, the LED will not shine at full strength. Sometimes it can even be helpful. For example, using an LED with a switch and a 3 V disk battery (popularly called a tablet) used in computer motherboards, you can make a small flashlight keychain. Such a miniature flashlight can be useful in different situations.

From such a battery - 3 Volt tablets you can power the LED

Using a couple of 1.5 V batteries and a commercial or homemade converter to power one or more LEDs, you can make a more serious design. A diagram of one of these converters (boosters) is shown in the figure.

The booster based on the LM3410 chip and several attachments has the following characteristics:

• input voltage 2.7 - 5.5 V.
• maximum output current up to 2.4 A.
• number of connected LEDs from 1 to 5.
• conversion frequency from 0.8 to 1.6 MHz.

The output current of the converter can be adjusted by changing the resistance of the measuring resistor R1. Despite the fact that it follows from the technical documentation that the microcircuit is designed to connect 5 LEDs, in fact, 6 can be connected to it. This is due to the fact that the maximum output voltage of the chip is 24 V. The LM3410 also allows the LEDs to glow (dimming) . For these purposes, the fourth output of the microcircuit (DIMM) is used. Dimming can be done by changing the input current of this pin.

How to connect from a 9V Krona battery

"Krona" has a relatively small capacity and is not very suitable for powering high-power LEDs. The maximum current of such a battery should not exceed 30 - 40 mA. Therefore, it is better to connect 3 light-emitting diodes connected in series with an operating current of 20 mA to it. They, as in the case of connecting to a 3 volt battery, will not shine at full strength, but on the other hand, the battery will last longer.

Krona battery power scheme

In one material it is difficult to cover all the variety of ways to connect LEDs to batteries with different voltages and capacities. We tried to talk about the most reliable and simple designs. We hope that this material will be useful for both beginners and more experienced radio amateurs.

If you ever want to power an LED with a single battery, sooner or later you will stumble upon a circuit called Joule Thief - thief of joules. This circuit is good for many: a small number of parts, you can use a dead battery, the assembled design is compact and will work from a battery with a voltage of only 0.6V. The classic scheme of this device can be found on Wikipedia. There are many variants of this scheme, attempts to optimize it. I will show you one of the variants of this design, which will allow you to light two 3-watt LEDs connected in series. Everything was put together quickly. Taking into account the rewind of the throttle, it took 20 minutes.

What you need for assembly:

Soldering iron, not a lot of solder and wires. Battery 1.5V or less, firm hands.
Transistor. I used KT630,

its maximum operating frequency is large, the collector current is higher than that recommended in standard circuits. In principle, you can use any NPN transistor with a gain of at least 150, for example, 2SC1815. One 10 kΩ variable resistor.

One electrolytic capacitor 47uF at 25V. A larger capacitor takes longer to charge and reduces the brightness of the glow. Any one diode with a reverse voltage of at least 100 V, because without load, the capacitor charges up to 30-45V.

One 0.01uF capacitor. Two 3 watt LEDs connected in series. Mounted on a radiator from a computer processor.

One group stabilization choke from a computer PSU.

You can use any ferrite ring that is at hand. I used the choke from the PSU, simply because it was. I didn’t count the number of turns, I just wound the entire wire from the ring (there are two wires of different sections) and wound it again, bifilarly.

The winding, wound with a wire of a smaller cross section, was included in the base circuit of the transistor. Accordingly, the second winding was included in the collector circuit. It is important that the beginning of one winding is connected to the end of the other, as shown in the diagram. you can wind a winding on a ferrite rod with a tap from the required number of turns, or in general, make a coil without a core.

Unlike the standard circuit, here, the load is connected between the base and the collector. The efficiency of the circuit depends on the capacitor, which is connected in parallel with the load. Such a load switching circuit was made in an attempt to use the OEMF that occurs in the L2 coil.

The video shows that when the resistor R1 is closed, the brightness of the glow increases.

LEDs have long supplanted incandescent bulbs in almost all areas. This is understandable: the LED is superior in brightness to the lamps, given its power consumption.
But LEDs also have a number of disadvantages. Of course, we will not talk about all of them, but we will discuss one. This is a high initial power threshold - it is about 1.8-2.2 volts. Naturally, you can’t power it from one battery ...
To overcome this shortcoming, we will build a simple transducer using the absolute minimum of parts.
Thanks to this converter, you can connect an LED (or several LEDs) to one battery and make a small flashlight.
We will need:

• Light-emitting diode.
• 2N3904 or BC547 silicon transistor, or any other n-p-n structure.
• Wire.
• Resistor 1 kOhm.
• Ring hearts or ferrite hearts.

Converter circuit

I will give you two diagrams. One for winding a ring transformer, the other for those who do not have a ring core at hand.

This is the simplest blocking generator, with a free excitation frequency. The idea is as old as the world. The device will have a high efficiency.

winding inductor

Regardless of whether you are using a ring core or a regular ferrite core, wind 10 turns of each winding. Your inductor is ready for this.

Generator check

We collect according to the scheme and check. The generator should work and does not need to be adjusted.
If suddenly, with serviceable elements, the LED does not light up, try changing the ends of one of the windings of the induction transformer.
Now the LED is very bright, even with a dead battery. The lower limit of the power supply of the entire device is now somewhere around 0.6 volts.
The efficiency of the transformer on the ring core is slightly larger. Not critical of course, but just keep in mind.

From a battery with a voltage of 1.5 volts and below, it's just not realistic. This is due to the fact that the bulk of the LEDs have a voltage drop exceeding this figure.

How to light an LED from a 1.5 volt battery

The way out of this situation can be the use of a simple one transistor and inductance. In essence, it is peculiar. The circuit is a simple blocking oscillator, powered by a 1.5 volt battery, which produces sufficiently powerful pulses as a result of pumping energy in the inductor. The circuit is simple and assembled in just 10 minutes.

Choke T1 is made on a ferrite ring having a diameter of 7 millimeters (its dimensions are K7x4x3). The winding contains 21 turns, made of double-folded enameled copper wire PEV with a diameter of 0.35 millimeters.

At the end of the winding, the end of one of the wires must be connected to the beginning of the other wire. The result is a tap from the center of the winding. By selecting the resistance, you can achieve better light output.