Can a flashlight shine without batteries? Of course, if it is an induction flashlight, or as it is also called, a Faraday flashlight. Why Faraday? Because it was he who discovered the phenomena of electromagnetic induction, that is, the emergence of an electric current in a closed circuit when the magnetic flux passing through it changes. It seems complicated and incomprehensible to you. It is better to comprehend theory through practice. We will make a flashlight whose operation is based on this principle discovered by Faraday.
Details
To make an induction flashlight we will need:
- white LED;
- diode bridge W10;
- transistor BC 547;
- resistor 1 kOhm;
- ferrite ring;
- copper wire in enamel insulation cross-section;
- switch;
- supercapacitor 1.5 F x 5.5 V;
- Neodymium magnets;
- plastic base for the coil (a solder coil will do);
- pieces of plastic pipes of different diameters.
Making a Faraday flashlight with your own hands
The first thing we will do is make an inductor. Let's take as a basis a plastic frame on which solder is sold. We will wind it using an electric drill. We will not count the turns when winding. The more we wind, the better. Let's take a wire with a cross-section of 0.5 mm.
Further.We choose a plastic tube of such a diameter that our magnets can move freely inside it. The newly made coil should be secured to this tube. We place magnets inside the tube and close the ends with plugs. We secure it carefully with tape and glue. To prevent the magnets from knocking when moving inside the tube, we glue foam rubber onto the plugs.
It's time for the flashlight's electronic circuit. The first part of the circuit is a rectifier for charging the capacitor. The second is a blocking oscillator on a transistor. This the scheme is also called “Joule thief”, can be translated as “LED. Turn on the flashlight. Works! It shines very brightly. The energy of the capacitor is enough for continuous glow LED for about 4 minutes.
This flashlight can be used as an emergency flashlight - it is always ready to use, and no batteries are needed.
