You’d think that we’ve posted every possible clock here at Hackaday. It turns out that we haven’t. But we have seen enough that we’ve started to categorize clock builds in our minds. There are the accuracy clocks which strive to get every microsecond just right, the bizzaro clocks that aim for most unique mechanism, and then there are “hello world” clocks that make a great introduction to building stuff.
Today, we’re looking at a nice “hello world” clock. [electronics for everyone]’s build uses a stepper motor and a large labelled wheel that rotates relative to a fixed pointer. Roll the wheel, and the time changes. It looks tidy, it’s cyclical by design, and it’s a no-stress way to get your feet wet driving stepper motors. And it comes with a video, embedded below.
The clock is driven by the ubiquitous 28BYJ-48 stepper motors that can be found on eBay for a few bucks. They don’t have much torque, but all they have to do here is turn a cardboard disk. It’s the perfect match.
There is one caveat with these motors, though: they don’t have an integral number of steps per turn. If you have the “1:64” geared version, it’s actually geared 8910:567424. The upshot? Instead of 2,048 steps per turn, you need 2,037.8864. Get this wrong and you’re losing 14 minutes per day with a 12-hour wheel.
So between just driving the motors, and the low torque and the non-integral gearing, there’s more to learn here than you’d think. You can add a real-time-clock circuit if you want it precise. With all this room to expand, you can get it built and running in a weekend for a few bucks. And that makes it the perfect “hello world”.