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.