LED POWER FROM A 1.5 VOLT BATTERY

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LEDs have long supplanted incandescent bulbs from almost all areas. It is understandable: the LED is superior in brightness to lamps, given its energy consumption.
But LEDs also have a number of disadvantages. Of course, we won’t talk about everyone, but we’ll discuss one. This is a high threshold for initial power supply - it is about 1.8-2.2 volts. Naturally, you cannot power it from one battery ...
To eliminate this drawback, we will build a simple converter using an 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 silicon transistor BC547, or any other structure n-p-n.
Wire.
1 k ohm resistor
Ring hearts or ferrite hearts.

Converter circuit

I will give you two schemes. One for winding a ring transformer, another 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.

Inductor winding

Regardless of what you use - a ring core or a regular core made of ferrite, wind 10 turns of each winding. Your inductor is ready for this.

Generator check

We assemble according to the scheme and check. The generator should work and does not need to be configured.
If suddenly the LED does not light up with serviceable elements, try changing the ends of one of the windings of the induction transformer.
Now the LED is very bright even from a dead battery. The lower edge 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 that in mind.