Often times as a young startup, you wave your hands about some piece of technology that is important for your product or service to work but is not part of the core experience. Like - “we’ll virtualize the servers” - “we’ll just put it in the cloud” - “the crowd will filter content for us”... For us we simply said “induction” as the way we’d charge Sphero. Little did we know that this one word would occupy so much of our engineering effort and literally almost kill our company - twice!
In 2010 when Sphero was just a rough prototype and a growing idea, no one knew anything about induction other than a basic understanding of the concept and a faint memory of a few forgotten mathematical equations. The first 6 months of our existence were spent focused on the mechanics of the ball and making Sphero actually drive in a constant direction. Around March of 2011 we started thinking how we would actually charge the ball and began to learn a few things that didn’t sound good.
Thing #1 - LiPo batteries are not meant to be sealed in an airtight vessel - they can be dangerous if not managed properly (the new Boeing 787 was grounded for months due to LiPo issues). We quickly learned that if we put LiPo batteries in Sphero we'd need to engineer numerous levels of safety controls. We could have used another type of battery but Sphero would only last for about 15 minutes before it needed to be charged. This put us into a spiral for about 2 weeks while we redesigned the battery compartment, the electronics and the shell to essentially contain anything that could go bad inside the ball. For a while we thought we were not going to make it.
Thing #2 - We mistakenly concluded that since induction charging is used on electric toothbrushes it should be easy to implement for Sphero. Nope. Sphero has two batteries in series - these need to be charged in a specific manner. Everything else on the market that uses induction in our price range has one battery. We searched for months until we found a chip set that worked with some custom firmware for our application. During this time frame we were thinking that we couldn’t do it at a reasonable price. Simple “wireless” chargers for smartphones sell for the price of Sphero - we had to build a more complicated charger for Sphero and do it for a fraction of the price.
Thing #3 - Sphero is a ball with a moving robot inside - there is no battery charging point. This was the hardest of all problems to solve. Most induction charging systems you get flat coils really close to each other to transfer power - we can’t do that with Sphero because the robot moves inside the shell - our coils aren’t flat or close to each other. Not a lot of examples to copy on this one. The math gets really complex with curved coils and a gap of 1cm. We ended up seeking the help of a CU professor Al Gasiewski to help us figure this all out. Here is just one image from a 28 page document on the math behind charging Sphero and the model used to design the circuit and coils. Along with the mechanical design and prototype coils.
It took 6 months to figure this all out. During that time we didn’t know if we could make a product that would work and be safe. There were many dark days when it felt like it was all going to fall apart.
We were naive and didn’t know better - sometimes that is the best way to make a breakthrough. If I knew how hard it would be to charge Sphero back in 2010 we would have never pursued the technology and Sphero would not be as magical as it is today.
The second time charging almost killed the business is even more exciting...
I recently found a Sphero at a local thrift shop but it didn't include the charger. I bought it thinking maybe I would get lucky and I could charge it with my tooth brush charger or build a charger for it. After reading this article I'm guessing I was wrong :( Is there anywhere I can buy just the charger?
Posted by: John Macy | December 15, 2013 at 08:31 PM