Two and a half hours passed.
He Gui finally stopped.
He straightened up, letting out a long breath.
He placed the green toroidal core, tightly wound with copper wire, on the tabletop.
The coils were arranged neatly, with four wire leads extending from either side.
He Gui rubbed his stiff neck. His fingers were trembling slightly.
Zhou Kai put down his pen as well.
He pushed the top sheet of scratch paper, covered in formulas, to the center of the workbench.
"The turns ratio for the primary and secondary coils is set to 1-to-1.5," Zhou Kai said.
"Based on this magnetic permeability, those are the easiest parameters I could calculate to initiate oscillation."
Chen Zhuo walked over and glanced at the toroidal core.
Then, he looked at Zhou Kai’s sheet of calculations.
"Let’s test it," Chen Zhuo said.
Wang Huashao pushed the breadboard over.
He Gui used a pair of tweezers to grip the four wire leads on the core. Lin Yi had already scraped the insulating enamel off them with sandpaper, revealing the yellow copper within.
Following the circuit diagram Zhou Kai had drawn, he carefully inserted the leads into the corresponding holes on the breadboard.
The primary coil was connected to the transistor’s collector.
The secondary coil was connected to the resistor on the base.
A Joule thief—the simplest form of a high-frequency, self-oscillating boost circuit—was now fully assembled.
Chen Zhuo took the multimeter and set the dial to the continuity test mode.
He touched the red and black probes to a few key nodes.
The multimeter emitted a short BEEP.
"We have continuity," Chen Zhuo said, putting down the probes.
Next up was the power source.
From the spare parts he had gathered earlier, Chen Zhuo picked up the black semiconductor cooling module.
It was square, like a thin ceramic wafer.
Two relatively thick wires, one red and one black, extended from its side.
He connected the module’s red and black wires to the circuit’s input.
"The target LED," Chen Zhuo said.
Wang Huashao carefully tore open the transparent plastic bag.
He took out the high-brightness red LED they needed to light up.
He glanced at its long and short leads to identify the positive and negative terminals.
He plugged it into the circuit’s output.
All the connections were complete.
On the workbench, the crude system—composed of old spare parts, thin wires, and a breadboard—lay silently.
It had no high-tech aesthetic; in fact, it looked downright shabby.
The time on the large screen read 01:10:00.
A little over an hour remained.
"Who’s going to warm this?" Chen Zhuo asked, looking at the black cooling module.
"I’ll do it." Wang Huashao rubbed his hands together.
He leaned forward.
He pressed his palms flat against the black ceramic plate.
He applied firm pressure.
His body heat began to conduct into the ceramic plate.
The Seebeck effect began to work.
Around them, some of the other provincial teams were still desperately adjusting the angles of their solar panels, while others had already given up on the pre-made components and started rummaging frantically through the bottom-layer boxes.
At Chen Zhuo’s workbench, everyone held their breath.
Zhou Kai stared at the red LED.
Miao Shian gripped the multimeter’s probes, pressing them firmly against the LED’s two leads as he stared at the LCD screen.
The red light flashed brilliantly, its brightness shooting up instantly.
"It’s oscillating," Miao Shian said, his voice trembling slightly. "Voltage is 2.64 volts. We’re past the threshold!"
One second.
Two seconds.
Three seconds.
Suddenly, a faint red glimmer flickered within the previously dark LED.
It was like a matchstick about to be extinguished.
And then.
The red light flashed brilliantly.
Its brightness shot up instantly.
A piercing red dot of light began to glow steadily from within the translucent epoxy casing.
It was lit.
A look of pure ecstasy erupted on Wang Huashao’s face.
He instinctively wanted to shout but forced the sound back down his throat, merely grinning from ear to ear as he looked at Zhou Kai and He Gui.
He Gui let out a long sigh, his tense shoulders finally slumping.
Zhou Kai clenched his fist and pumped it in the air.
They had used a pile of the most unremarkable spare parts and a crude, hand-wound coil.
Somehow, they had taken human body heat, bridged a massive voltage gap, and boosted it to 2.5 volts.
"Hold it steady," Chen Zhuo said, looking at Wang Huashao. "The target is ten seconds. Don’t let go."
Wang Huashao nodded, continuing to press his palms firmly against the cooling module.
Four seconds.
Five seconds.
Six seconds.
The red dot of light remained piercingly bright.
Under the control of the high-frequency switching, a stable current flowed continuously into the diode.
Seven seconds.
Without any warning, the piercing red dot suddenly flickered.
Its brightness dimmed visibly.
"The voltage is dropping!" Miao Shian snapped his head up.
"2.1 volts... 1.8 volts... It’s fallen below the threshold!"
The piercing red light faded to an orange-red.
"0.6 volts... 0.2 volts..." Miao Shian’s voice sank as he watched the numbers on the screen.
Wang Huashao froze for a moment.
"What’s happening?"
Thinking his hands had slipped, he quickly readjusted his posture, pressing his palms desperately against the ceramic plate.
Eight seconds.
The red light did not return.
Instead, it rapidly faded from a bright, piercing red to a dull, orange-red.
It was like the last gasp of a dying battery.
Nine seconds.
The orange-red completely vanished.
Only a barely-there, dark red filament remained within the LED.
Ten seconds.
The light went out.
The light-emitting diode on the breadboard once again became a lifeless, transparent plastic shell.
Wang Huashao froze in place.
His hands were still pressed tightly against the cooling module.
But the light never came back on.
The air around the workbench seemed to freeze in an instant.
The elation of the last ten-odd seconds was shattered into a million pieces by the sudden failure.
"Did a wire break?"
He Gui’s voice trembled. He immediately leaned in to carefully inspect the copper wires on the toroidal core and the pins on the breadboard.

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