Tuesday, December 25, 2012
Well, folks, I thought I would mark the season on a more personal note than usual. I wanted to share with you a small Christmas present I got for myself. This is the motor unit from the cheapest ceiling fan available from Home Depot… $25 USD. I bought this because I am toying with the idea of building a working scale model of the SMART PRT platform. This is something that has been in the back of my mind for a while, but I have always been thinking small – like 1/8th scale. That degree of miniaturization, however, gives little leeway, dimension-wise, and so requires a lot of specialty parts and machine shop work. As I was browsing the internet, looking for useful robot parts, I noticed that most of the affordable components were of a size more suitable for a quarter-scale model. It turns out that if you want to build something like this a good size is the dimensions of a battlebot. The downside is that any track layout won’t be something you can put in the spare bedroom! Nonetheless, I started looking for hub motors that would fit in a 6” wheel. Unfortunately even the ones for bicycle conversion seem to be too big, and not exactly what I would want anyway. I was, however, reminded of various Youtube videos which explain how to make little wind generators out of ceiling fan motors by placing rare earth magnets around the inside of the casing. This is, in essence, also a brushless DC hub motor, and if you rewire the coil leads, it could be given the characteristics of a multi-polar stepper or servo motor. This motor happens to be exactly one quarter scale, if you add a little rubber around the outside for traction.
Anyway, the idea appeals to me, and so I am exploring what it would take… even though the last thing I need is a new project. I have too many ongoing ones already! I must confess, though, that I have drawers full of electromechanical junk that I would like to find a use for and robotics has become an increasingly affordable hobby and one I have always wanted to dabble in. Also, maybe the robotics aspect of this project is something that would attract a whole new crowd. After all, the swing-arm aspect of the design is not all that different from the standard three-axis articulating arm that is standard on industrial robots. There are high school kids making these things nowadays. It can be even be done with Legos.
This is what the motor looks like inside, with the outer inductive ring removed. (The ring pulls the outer case around.) Actually there is quite a lot of space.
Well, I’m not going to rush out and buy the other three fans quite yet. With stuff like this I need to hold off a bit, dip my toes in, and make sure I’m really up for it, or it will just become more junk for my collection. But I really had to at least pop one of these things open to see for myself, and, after all, it IS Christmas… Happy holidays!