The availability and relatively low prices of super-bright light-emitting diodes (LEDs) allow them to be used in various hobbyist devices. Novice radio amateurs who use LEDs 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, which LED connection schemes can be used in one case or another, how to calculate the circuit elements.

What batteries can i connect the LED to?

Basically, you can just light the LED, you can use 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, be it a chemical element or a battery, is its capacity. Battery capacity - C is expressed in ampere-hours. For example, the capacity of common AAA AA batteries, depending on the type and manufacturer, can range from 0.5 to 2.5 ampere-hours. In turn, light-emitting diodes are characterized by an operating current, which can be tens or hundreds of milliamperes. Thus, you can roughly calculate how long the battery will last 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 that the light-emitting diode consumes. The formula does not take into account the efficiency of a specific 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 keep their current consumption not exceeding 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 AA 1.5V finger 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 lies in the range of 3.2 - 3.4 V. 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 an operating current of 20 milliamps.

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

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

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

Transformer T1 can be wound on a ring made of ferrite grade 2000NN. 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 0.3 mm in diameter, 25 turns each.

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

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

How to connect from a 3V battery

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

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

Using a pair of 1.5V batteries and a commercially available or homemade converter to power one or more LEDs, a more serious design can be made. A diagram of one of such converters (boosters) is shown in the figure.

A booster based on the LM3410 microcircuit 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 9V batteries Krona

"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 series-connected light-emitting diodes 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.

Crown battery power circuit

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