Chapter 6 — Wind Village Robot Team

All day Sunday, three people sat huddled under the porch of Mr. Tu's house - the only place with an outdoor electrical outlet to plug in the soldering iron - fussing over a pile of components spread out on an old tarp. Gia Han typed each line of command on the laptop borrowed from Khanh Dan, read it out loud to the other two before loading it into the board, while Phong held the soldering iron and carefully connected each sensor leg, holding it so firmly that he did not tremble even though the soldering iron was two hundred degrees hot, just a few centimeters away from his fingers.

"If we drive to the left, we should accelerate the right wheel, right?" Gia Han asked, her eyes still glued to the screen.

"Yes, but don't accelerate suddenly, increase gradually, otherwise the car will jerk." Khanh Dan replied, holding the wooden frame for Phong to drill screw holes. "That's called proportional control. The more deviation, the stronger the adjustment; the less deviation, the softer adjustment."

On the first try, the car drove straight off the black line right at the first turn, crashing into Mr. Tu's leg who was drinking tea nearby. The old man just smiled, lifted his foot to the side, and continued sipping tea as if this was nothing unusual in his house. The second time, the car was halfway down the road when a wire came off because the weld was not strong. On the seventh time, nearly six o'clock in the afternoon, when the sunlight turned yellow on the corrugated iron roof, the car finally crawled the entire winding road without missing the line once.

No one cheered loudly. Gia Han just let out a long breath, Phong nodded very softly, and Khanh Dan stood silently watching the car reach the final stop. The feeling was exactly like the first time watching the experimental robot of the Falcon project make its first round in the company warehouse - except this time, there was no one standing behind her counting down the budget time, only the sound of a dog barking in the distance and the smell of Mr. Tu's cold tea.

"Can I bring it to Mr. Nghia tomorrow?" Phong asked, his voice had a rare bit of nervousness.

"I'll see you tomorrow, teacher." Khanh Dan replied, carefully packing up the excess electrical wires. "But remember, the teacher will ask very carefully, not just complimenting for fun."

***

The small car rolled slowly down the hallway of the principal's office, the two rear wheels turning evenly thanks to a deceleration motor removed from an old printer. The body of the car was a rectangular piece of plywood hastily cut with a handsaw, the edges were still scratched and hadn't had time to be filed. It crawled along the exact line drawn by Khanh Dan's black marker on a piece of cardboard spread out on the floor. At a sharp turn, it stopped for a second, adjusted its direction, and then continued to crawl along the black line until it stopped completely at the end of the piece of cardboard.

Teacher Nghia stood with his arms crossed, looking at him, not saying anything the whole car ride. Two other teachers standing next to him - Ms. Hien, homeroom teacher of 9B, and a Geography teacher - also silently watched, their eyes more curious than trusting.

"Does it know its own way?" Teacher Nghia asked, when the car had completely stopped.

"Yes, it has two infrared sensors mounted under it, detecting black streaks that are different from the surrounding white background." Khanh Dan explained, kneeling down and flipping the car over to show everyone the two tiny sensor eyes attached to the bottom. "When one side deviates from the black line, the control circuit automatically orders the wheel on that side to rotate slowly, and the other side to rotate faster, so that the car can adjust itself to the correct road."

"When did you do this?"

"We did it last weekend." Gia Han answered instead, standing next to Khanh Dan, still holding the spare electrical cord. "Miss Dan wrote the main command, Phong and I installed the circuit and soldered the wires."

Mr. Nghia bent down to take a closer look at the car. The welds were a bit clumsy, one wire was fixed with electrical tape instead of heat shrink tubing because they didn't have any, and the car frame clearly showed traces of a piece of plywood that used to be the lid of some old storage box.

"How much does this cost?" He asked, and that was the question Khanh Dan was waiting for the most.

"No money, other than thirty thousand for the battery." She replied. "The motor was removed from a broken printer in the office, the Arduino circuit I borrowed from an old friend, the wooden frame is a plywood board that was liquidated at a carpentry workshop near the market, the infrared sensor was removed from two broken TV remotes."

The Geography teacher laughed softly, not in mockery, but in surprise. "Can a broken TV remote also work as a sensor?"

"Inside each remote there are infrared transmitter and receiver eyes, teacher, just need to separate them and reuse them properly." Phong spoke for the first time since the beginning of the session, his voice was still small but no longer hesitant like the first time Khanh Dan met him. "We tried three broken remotes before finding two usable ones."

Teacher Nghia stood up straight, looked in turn at Khanh Dan, then Gia Han, then Phong, as if considering something beyond the small wooden cart lying still on the floor.

"Did you invite me out here to see the toy car, or are you proving something else?" He asked directly, but his voice was no longer as sharp as last time in the office.

"I'm proving that without a budget, without a modern room, our students can still make something that works, with real technical principles." Khanh Dan replied. "And you're proving it with the two students I'm most worried about - one student has average grades because she's busy supporting her family, and one girl is preparing to take the transfer exam. Both of them can still do it, without missing a single class."

Ms. Hien, who was standing next to her without saying a word from the beginning, suddenly spoke up. "Gia Han is a student in my homeroom class. Last week her Math test score increased compared to last month. I wonder why she studies harder these days."

Teacher Nghia was silent for a long time, his eyes still looking at the small car lying on the floor of the hallway, the car's propeller still rotating slowly according to inertia before stopping completely.

"Okay." He spoke finally, his voice somewhat reluctant but decisive. "I'll give it a try for one semester. But there are three conditions, Ms. Dan, listen carefully."

Khanh Dan nodded, her heart beating faster.

"One, all club activities that take place after 16:30 do not interfere with any regular classes, including drums or class activities." Teacher Nghia raised a finger. "Two, the average score of each participating student's subjects must be reported to me every two weeks, through the homeroom teacher. If any student's score drops significantly, I have the right to ask that student to stop immediately, without discussion."

"I agree." Khanh Dan said.

"Three." He raised a third finger, looking straight at her. "The school does not allocate any budget for this activity. Since you said so yourself, I will write it down in the minutes to make it clear. Regarding the location, you ask Mr. Toan if the warehouse behind the kitchen can be used. I will sign for a temporary loan, but electrical safety must be your own responsibility. I don't want to hear about any fires in the school."

"I accept all three conditions." Khanh Dan said, trying to keep her voice calm even though inside she wanted to scream.

Teacher Nghia nodded and turned to Ms. Hien. "You make a record of this meeting. I'll sign it today, so that Miss Dan doesn't have to run up and down asking for an autograph many times."

He turned back to look at the small car one last time before going into the office, and in that brief moment, Khanh Dan saw an expression on his face that was very different from the rigid reserve in the previous meeting - not quite complete trust, but something close to the curiosity of a person who once in his youth wanted to try something no one else had done, but because of work pressure, he no longer allowed himself to be curious for a long time.

"What is the name of this car?" He asked, stopping at the door of the room, not turning around completely.

Khanh Dan looked at Gia Han, then looked at Phong. They both shook their heads, clearly never thinking about naming a wooden frame to run a test line.

"Not yet." She replied.

"So think about it." Teacher Nghia said, his voice had lost the seriousness of an official meeting. "If something has a name, people will easily remember it and retain it for a long time."

He entered the room, closing the door behind him. In the hallway, the remaining three people stood looking at each other for a while, no one said anything, until Phong bent down to pick up the wooden cart, turned it over to check the two infrared sensors as a professional reflex, and then suddenly burst out laughing - the first laughter Khanh Dan had ever heard from this student who was always quiet.

"So that's okay, miss?" He asked, still surprised.

"Alright." Khanh Dan replied, and this time she let her smile fully bloom, not trying to maintain her professional composure like during the last meeting. "Now we need more people. And we need to name this car before it forgets that it just saved our entire plan."

Gia Han hugged the wooden car in her arms like hugging a newly rescued pet, her fingers gently stroking the plywood layer that still had scratches on its edges. "Let me think of a name, give me a few days." She said, her eyes shining in a different way than her usual reserved expression. Phong didn't say anything, just stood nearby nodding, his eyes still glued to the two infrared sensors under the car, as if he was thinking about where the next version would improve.