Two singing Tesla coils from the performance group Arc Attack delight kids during setup day at Maker Faire.

SAN MATEO, Calif.--"They're putting Josh in the cage!"

It was early this afternoon, and a group of school kids were excitedly screaming those words over and over. And it was true. A kid called Josh was being put inside a cage that was part of a performance by a group called Arc Attack. Soon, the cage would be bombarded with electricity from two of Arc Attack's signing Tesla coils. No Joshes would be harmed in this experiment. But an awful lot of grinning would be done.

This is Maker Faire. Well, almost. The famous DIY festival begins in earnest tomorrow morning, and over the course of the weekend, in excess of 100,000 people may well get themselves to the San Mateo County Event Center here to see countless examples of do-it-yourself robotics' 3D printing' steampunk kinetic sculptures' and much, much more.

But today was setup day, the day the thousands of so-called "makers" arrive, drop their gear, and start building the projects they'll show the tens of thousands of visitors over the next two days. Being at Maker Faire on setup day is both a treat--it's always great to see the process behind something as cool as Maker Faire, and it's nice not to have to compete with 50,000 people to see something--and a curse: Only about half the projects are finished.

One thing that's definitely cool about being on hand for setup day is that each and every time you return to a specific spot, there's more there than there was the last time you went by. Even if that was just 30 minutes ago. A steady stream of trucks, vans, cars, and other conveyances arrive, and with them, the festival comes to life.

Maker Faire started here in 2006, and is now a worldwide phenomenon. From 20,000 visitors that first year to 80,000-plus last year, attendance figures are now expected to hit six figures. At the same time, the festival has planted its flag in other cities, such as Austin and New York.

But at its heart, no matter how many people there are, and no matter if the projects are new to the event or have been featured at several of the fairs, the idea behind the festival is simple: show visitors that it's not so hard to make things yourself, and inspire them to give it a try. And it works. Many return for their second or third years with a project.

Education day Of course, the best way to kick that dynamic into high gear is to start with kids. So today was, in addition to being setup day, also Maker Faire Education Day. And more than 1,300 school kids were on hand to check out what the festival has to offer. According to Michelle Hlubinka, who coordinates Education Day, 90 percent of the kids who showed up today came from disadvantaged communities, so this might have been the first time many of them had ever seen projects like the ones that proliferate here.

Hlubinka is also involved with the Young Makers program, which was featuring nearly 100 kids who had brought about 40 of their own projects along. Those projects ranged from the Water Totter--a see-saw that pumps water to a fountain--to the FireJam, a guitar with exploding fire jets.

And everywhere today you'd run into the kids. Whether they were watching with the widest of eyes as Arc Attack did its thing, or sitting by trying to stay dry as Eepy Birds did their famous Mentos and Diet Coke explosion performance, these future stalwarts of the DIY movement were blossoming in front of my eyes.

The Eepy Birds demonstrate what happens when you drop Mentos into warm Diet Coke.

"This means a lot to me to see all the kids here who may not get to see Maker Faire otherwise," said Dale Dougherty, one of the lead organizers of the event.

One project that was attracting a lot of kids was Andra Keay's The Robot State. This is part of Keay's thesis project, which is a study of playing with robots and what doing so means.

Kids were swarming to her booth, where Keay was processing "applications" for the Robot State. She would ask them three questions: what are the names of three different robots you know of' what are robots' biggest achievements' and how do you see yourself in the future of human-robot relations.

Keay explained that most people answer the first query with the names of fictional robots and that the question usually throws people off so much, they don't even know how to respond to the second. But ultimately, she said, her work is about trying to discover some of the truths that lie in human-robot interactions. One thing she said she's noted in her research is that just about anyone who builds a robot names it, even if their projects are not about social robots. "We like names," she said. "You want to work on something. We like naming things." She wants to study the stories behind the names people give their robots.

Electric giraffe One of the most reliable Maker Faire favorites is Lindsay Lawlor's Electric Giraffe Project. This giant electric giraffe robot, which Lawlor has been bringing for years, walks and even talks. It features tons of LEDs, and this year, Lawlor's team has engineered it to give "LED feedback," in the form of lights that turn on when someone scratches the giraffe's chin.

As well, this year's version of the creature has a new neck, with seven segments so that it more closely resembles a real giraffe's neck. All in all, the 2011 version of the Electric Giraffe Project is "a little smarter, and a little more talkative," Lawlor said. That means it has more sensors and responds verbally to more outside input. And it has an improved voice, as well as a better vocabulary, he said. Next time, he added, the giraffe could have computer vision that recognizes symbols, and which could allow the creature to say hello when someone walks up to it.

Though Lawlor's project has been at Maker Faire for years, as have many others, there are plenty of makers who brought entirely new things with them this year. Dougherty said 50 percent to 60 percent of the projects at this year's fair were new.

One exhibitor making its first visit is General Electric Research, which brought several projects from its base in Niskayuna, N.Y.

One was the InBody electrical impedence scanner, which Jeff Ashe, an electrical engineer in the biomedial electronics group at GE Research, said was about coming up with new measurements to replace the body mass index (BMI) used for so long to tell people about whether they're overweight.

The InBody system is designed, Ashe explained, to measure someone's lean mass, water content, and fat mass, which together produce a body fat percentage figure that means much more than the BMI, he said.

The device doesn't offer recommendations, only data. But Ashe said doctors are beginning to use it as a replacement for a BMI measurement.

Another GE medical project on display was what Ashe said is called a medical monitor system. Based on a simple GE home-security motion-detector system, the device has been hacked by GE researchers who discovered it can also measure someone's breathing and heartbeat.

That means, Ashe said, that sleeping patients can be monitored without being hooked up to anything, and doctors or nurses can determine if they're breathing properly, or if their hearts are beating as they should. Oddly, while this clearly has applications throughout the medical and nursing fields, the funding for the project came from the prison system, which Ashe said is concerned with monitoring potentially suicidal inmates who refuse to be hooked up to any wires. If the system detects abnormal breathing or heart rates, it can trigger an alert.

General Electric, of course, wasn't the only large company with exhibits here. Google was also present, with a team from Sketchup, and with robotics and Android projects to show off.

Yet the heart of Maker Faire is almost certainly the thousands of individual makers who toil away in their garages working on projects that may only see the light here. Some, like Arc Attack, come from hundreds, or thousands, of miles away, and all because they're bound to make a lot of people happy.

Like Josh. How could any kid not love the idea of being inside a cage while two Tesla coils blast it with lightning bolts in time to the Imperial Death March music from "Star Wars" I didn't get a chance to be inside the cage. But if I had, I know I would have been smiling from ear to ear.

If you visit Maker Faire this weekend, expect to see a lot of that.