My IQ has been increasing year by year.

Chapter 72 The Red Light of the Indicator Light

Day 14.

The last day of training camp.

Two o'clock in the afternoon.

The sunlight outside was extremely intense, and the cicadas in the trees were chirping loudly and shrilly.

The air conditioning in the lab was turned up to the maximum.

Professor Wang did not sit in the corner.

He stood in front of the podium.

On the table was a messy cardboard box without any blueprints.

Inside were springs, brass gears from an old clock, photoelectric gates, capacitors of different capacities, a rough relay, and a few broken wooden strips.

"The last question."

Professor Wang looked at the six teenagers, whose naivety and individualistic pride had completely faded, and whose eyes had become calm and composed.

"There was no test paper, and no hints."

"Use the scrap metal in this box."

"Build me a mechanical and electrical alarm device that can precisely control the delay of three minutes."

"The use of any off-the-shelf digital chips is not permitted."

"Only purely mechanical and analog circuits can be used."

Professor Wang raised his wrist and glanced at his watch.

"Three hours, let's begin."

He didn't go back to his seat, but stood in front of the podium looking at them.

Six people.

Lin Yi stepped forward.

I picked up a pencil and rummaged through the cardboard box.

Water droplets? Not precise enough.

Pure circuit RC charging and discharging? The error is too large.

She picked up a brass pendulum with gears.

I quickly sketched a draft on the paper.

"A mechanical pendulum controls a photoelectric gate, which charges a capacitor and accumulates voltage in steps."

"When the threshold is reached, the Zener diode breaks down, triggering the relay."

Lin slammed a piece of paper down in the middle of the table.

"Mechanical systems provide a stable cycle, while circuits provide the cumulative threshold; that's the general direction."

After saying that, she stepped aside and leaned against the lab table.

Chen Zhuo naturally pulled the paper in front of him.

My brain is working at lightning speed.

The ballpoint pen writes down lines of parameters on the paper.

"The pendulum has a fixed length of 24.8 centimeters and a period of approximately 1 second."

"It requires 180 blocking of the photoelectric gate."

"Each time the battery is blocked, the charging time is 0.1 seconds."

"Use a 1000μF capacitor."

He raised his head.

"Zhou Kai, calculate the amplitude decay equation for a simple pendulum under air damping. I need to add a dynamic compensation coefficient to the charging resistor."

"it is good."

Zhou Kai pulled out his pen and immediately began integral calculations.

"Miao Shih-an, when soldering the light-receiving parts, keep the leads as short as possible to reduce parasitic capacitance."

"receive."

"Wang, you're a man of few words. Use wooden strips to build up the pendulum's support. Make sure it's perfectly vertical and doesn't wobble."

"no problem."

"He Gui, connect the multimeter to the main capacitor and report the voltage at any time."

"clear."

The instructions were clearly given.

The laboratory instantly entered a high-pressure assembly state.

Wang, with few words, deftly assembled the wooden frame with a saw and glue.

Miao Shi'an wore an anti-static wrist strap and precisely applied soldering iron tips.

Zhou Kai wrote down the last line of the compensation formula on the paper and handed it to Chen Zhuo.

Based on the formula, Chen Zhuo connected a tiny adjustable resistor in series next to the capacitor.

I gently turned it half a turn with a screwdriver.

Locked up.

Lin Yi walked around the table.

Occasionally, he would extend a finger.

"The gears are meshing too tightly; add some lubricant."

"The cable is too long, so we need to run it close to the board to prevent interference."

Two hours and forty-five minutes.

An ugly device, devoid of any outer casing, with countless wires exposed like blood vessels.

It was placed quietly in the very center of the lab bench.

On the left is a brass pendulum supported by a wooden frame.

On the right is a perforated board densely covered with soldered components, connected to a small red light bulb.

Professor Wang was holding an old mechanical stopwatch.

He walked to the table.

"alright?"

Professor Wang looked at them.

"alright."

Chen Zhuo answered calmly.

"Power on, prepare."

Professor Wang held up his stopwatch.

Chen Zhuo placed his hand on the power switch.

Wang Huashao held the brass ball of the pendulum and pulled it to a precise angle.

"put."

"Click".

The switch is pressed.

The pendulum is released.

"Tick-tock".

The stopwatch clicked simultaneously.

The brass pendulum smoothly glides across the lowest point under the influence of gravity.

The faint beam of light from the photoelectric gate was cut off.

On a perforated board.

A tiny current pulse was sent into the 1000uF capacitor.

The entire laboratory.

Silence fell instantly.

Only the regular, whistling sound of the pendulum cutting through the air.

And on the multimeter, the voltage reading climbed slowly but steadily.

One minute.

Two minutes.

The amplitude of the pendulum begins to decrease slightly due to air resistance.

But Chen Zhuo's precise compensation resistor worked perfectly.

The rate of voltage increase did not slow down at all.

Two minutes and fifty seconds.

The voltage reading is approaching the breakdown threshold of the Zener diode.

The breathing of the six people unconsciously became shallow.

Two minutes and fifty-five seconds.

Two minutes and fifty-eight seconds.

Two minutes and fifty-nine seconds.

The brass pendulum swept across the photoelectric gate once again.

"Smack."

A crisp sound of the relay clicking shut.

On a perforated board.

That ordinary little red light bulb.

It lit up instantly.

It emitted a blinding red light.

"Click."

Professor Wang pressed the stop button on the mechanical stopwatch with his thumb.

He lowered his head.

Looking at the hands on the stopwatch dial.

Zhou Kai leaned over and took a look.

His eyes widened slightly.

three minutes.

Or, to put it another way, three minutes and 0.05 seconds.

This group of junior high school students.

It was made from a pile of crude scrap metal.

They managed to create a mechanical-electronic timer with an error of less than 0.1 seconds.

The afterglow of the setting sun.

The light shone through the somewhat dirty glass window of the laboratory onto the rough device with a red light on.

It also hit the faces of these six people, who were covered in sweat and whose clothes were covered in dust.

The red light of the indicator light.

It was steadily lit in the slightly dim laboratory.

There was no flickering.

It did not go out.

It was like an extremely long and agonizing dream that finally bore the most solid fruit.