There is no doubt that this thing can really send messages out, and at this moment, Li Younan can only marvel at Tesla’s greatness.
No wonder he was the man closest to god; in this era of information explosion, the one who first invented the radio truly surpassed his time.
Even though Li Younan now possesses many top-notch skills, he has no way to transcend his era.
But now is not the time for marveling; in order to ensure the radio can continue to be used, Li Younan began to immerse himself in the creation of a hand-crank generator.
The hardwood frame of the airplane seat can be used directly. Li Younan’s idea was to first use the wooden board to piece together a square wooden box to be the shell of the hand-crank generator.
Anyone who has studied middle school physics knows that the principle of power generation is extremely simple: cutting magnetic field lines causes current to flow.
A generator’s core generating components are only three: one is a permanent magnet, the source of the magnetic field, which is available from the emergency compass’s neodymium iron boron magnet; next is the rotor coil, and among the parts Li Younan dismantled, the most abundant is the enameled wire, so the coil is easily solved; and then the gear set for transmission, which Li Younan can easily make using woodworking tools. As far as he’s concerned, as long as there are tools, precision is not a concern.
He also found a usable bearing in the engine part; with this, the final formed generator will have much greater stability while rotating.
Because Li Younan had already considered making a hand-crank generator before, he had already made the gears in his spare time, assembling this hand-crank generator didn’t even take two hours.
The final product even comes with a gear that increases speed. He tried turning it, and the rotor coil rotated between two magnets, cutting the magnetic field lines. Li Younan estimated that if he rotates at a speed of 80 turns per minute, the power output would be about 5 volts.
However, the electricity generated like this cannot be used to directly charge a battery.
Because the rotation speed cannot be constant, the voltage will definitely fluctuate, easily breaking through the battery protective plate, or even damaging the battery cells.
But the solution is simple. Just make a voltage stabilizing and distribution module.
The principle is simple too; it relies on the voltage drop of silicon diodes for voltage stabilization, and with a shunt resistor to limit the current, it can be realized.
These electronic components can be found easily in the airplane, and diodes can be found in those damaged bulbs. When Li Younan was sorting out the parts, he had already collected all the rectifying diodes removed.
He took out the silicon rectifying diodes, and then used pliers to twist a thin steel plate into a U-shaped clamp, then used woodworking tools to chisel a slot on a piece of hardwood, embedded the diode in it, and clamped the leads with the U-shaped clamp.
After calculation, the series of diodes can stabilize the output voltage at 3.7 volts, completely matching the lithium battery he is currently using.
Next is the current limiting protector, the principle is to form a parallel circuit between the resistor and battery, automatically shunting the current when it’s too large.
Finally, to make this hand-crank generator useful, Li Younan optimized its structure again, fixed the voltage stabilizing module and hand-crank generator on a wooden board, and added a small electric bulb, embedding this bulb in a small hole of the current limiting module; as long as the bulb lights up, it means the voltage is stable within the safe range.
After finishing this hand-crank generator, merely two or three hours had passed, and Li Younan gave it a try. When he started to turn the crank handle, the bulb lit up.
Eagerly, he connected the battery to the hand-crank generator, thinking to himself, physics is truly great.
Mastering math, physics, and chemistry makes you fearless wherever you go, and in such wild environments, it’s truly useful. If one day an apocalypse occurs, physics would surely be the most useful subject.
This hand-crank generator didn’t use any voltage measuring equipment, relying solely on the fixed voltage drop characteristic of diodes, it was made entirely without soldering or measurement instruments, and it could provide stable current.
Also, with the gear that increases speed, Li Younan doesn’t need to turn very fast to easily achieve stable charging.
If he just cranks for half an hour or so, he can roughly refill the energy of this small battery.
Just as he enthusiastically continued to charge, a certain sound suddenly came from above, a sound... different from the sea wind’s roaring vibrations, "buzz buzz buzz buzz—"
Not an illusion, it was an engine’s sound!
Deep and stable, moving closer from afar.
Action even preceded thought.
Li Younan turned and rushed out of the hut.
A helicopter was very conspicuous under the sapphire sky.
Even Li Younan couldn’t hide his excitement, even feeling a trace of worry because of it.
Was it the rescue team that received his SOS signal? Or was it just passing by? Did they see his hut? Did they see the SOS sign on the beach?
But before Li Younan could jump up and gesticulate wildly to call for help, the engine sound got closer; the aircraft lowered its altitude with a clear intention to hover.
Li Younan took a deep breath, forced himself to calm down, but in that instant, tears still moistened his eyes, he rubbed his somewhat aching nose: "Damn, I’m saved..."
The aircraft gradually descended, becoming clearer to see, the altitude continued to decline.
At that moment, what surged in his chest was not only the wild joy of being rescued but also a huge, almost unsteady softness and relief.

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