Where to get a small freewheel?

Hi,

I’m in need of a small freewheelto use on my project, and I hope someone here will know of a place to get one.

The project is this: I found an old digital flip-clock in my neighbor’s trash. I removed the flip clock mechanism and I have a microcontroller driving a stepper motor to set the flip clock’s time automatically. (The time comes from a GPS module. I can detect when the flip clock advances past midnight by setting the clock’s alarm to midnight - the alarm triggers a switch. From there, I just track how much I turn the setting wheel.)

Everything works great. But after hours of operation, the clock stops advancing. The problem is that the setting wheel is supposed to turn slowly as time elapses. The stepper motor, even with no power to it, has enough inertia that the shaft of the setting wheel can’t turn. After several hours, the clock stops.

So I figure I need a freewheel to allow the shaft to turn when the stepper isn’t moving, while still allowing the stepper to rotate the shaft. It’s diameter should be on the order of an inch.

I’ve never seen such a thing for sale. If you know a source, I’d be grateful for your help.

Thank you,
Bob

If the stepper motor is “in control” of the motion, in what situation(s) would the flywheel take over?

Not a flywheel, a freewheel. Think of a bicycle: when you pedal, the gear turns the wheel. But when you coast, the wheel spins free. So the gear isn’t fixed to the wheel: there a mechanism so that when the gear is turning faster than the wheel, it grabs the wheel and accelerates it, but when the gear stops moving, the wheel is still free to rotate.

Likewise, when my motor isn’t driving the clock’s setting wheel, I want the setting wheel to be able to rotate freely.

Understood. At this time we don’t have any particular sources for this type of product, nor do we have any suggestions aside from a Google search.