The miniature assembly lines sit behind glass doors, where tiny bobbins are quickly wound with 2 meters of barely visible wire, and little sparks weld the copper ends in place.
Every day the new production facility in Santa Rosa can produce 90,000 magnetic sensors, each less than a quarter inch in length.
Such assemblage used to be done largely by hand in Asia, but the work returned to the United States last summer as the Santa Rosa company geared up production to supply key components in a new gaming system: the Nintendo Wii U.
The Wii U, released last week, utilizes the magnetic sensor and motion tracking technology of Santa Rosa's PNI Sensor Corp.
"No one's expecting us to be in this product," said Becky Oh, PNI's president and CEO.
The motion sensor industry is dominated by companies that make even smaller devices for smartphones, Oh said. But PNI impressed Nintendo by demonstrating the superior accuracy of its system.
"They needed the performance," Oh said. "They were really adamant about the performance. ... They wanted it to work everywhere and anywhere."
While many U.S. companies have outsourced manufacturing overseas to cut costs, PNI decided to bring production back home. And while touting better quality control and more involvement between designers and producers, company officials said making sensors in Sonoma County also saves money.
Oh said that, in 2004, a sensor for a radar detector cost 50 cents in the U.S. but only 12 cents in China. Now, while declining to give the exact numbers, she said it cost less to build the devices in Santa Rosa.
PNI has 34 employees and has grown by 50 percent since last year to support the Nintendo initiative. The company had $8.9 million in revenue last year. Oh predicted that sales will climb 50 percent by the end of 2013.
PNI was founded in 1987 by a group of Stanford University students. The company moved to Santa Rosa in 1998.
Its first product was a digital compass for cars. Over the years the company has produced a radar detector/compass and a breathalizer, as well as a compass built into a Timex watch.
But in 2005, Oh said, the company's leaders decided to focus more on its core technology of magnetic sensors and motion tracking.
The sensors also are used in robotics, laser range finders and weather buoys. About 95 percent of today's car compasses use the company's technology, Oh said.
Dick Herman, president of 101 MFG, an alliance of manufacturing executives in Northern California, said PNI demonstrates the cost effectiveness of U.S.-based manufacturing when skilled workers use state-of-the-art production tools.
"It's a big success story," Herman said.
Nintendo's original Wii had a motion sensing system that was "fairly imprecise" but still ushered in a whole new way of gaming, said Ari Greengart, research director for consumer devices at Current Analysis research group in Sterling, Va. It attracted a new group of casual players who took part in games like Wii tennis, golf and bowling.
"Motion gaming was a dramatic departure from what we had in the past," Greengart said. "This actually got you off the couch."
While increased motion accuracy will be appreciated by today's gamers, the Wii U is drawing attention for a different feature that Greengart characterized as "another conceptual leap in game playing."