[time-nuts] Building a mains frequency monitor

[Chuck Harris]

A more modern name for a synchronous motor is a permanent
magnet stepper motor.  Any PM stepper, and a couple of
microfarad capacitor becomes a synchronous motor when
connected to the power line.

-Chuck Harris

jimlux wrote:

>   Alternatively, use a
>> synchronous motor driving a load with sufficient inertia in combination
>> with a slotted disk and photo pickup. Perhaps an old record turntable
>> will do - but not one with a regulated DC motor.
>
> A clever idea because of the mechanical low pass filtering, but probably impractical..
>
> A record turntable with a synchronous motor?  That's going to be ancient and hard to
> find in this age of digital music players. People like us would happen to have
> something in the garage.. but for a science fair project, unlikely that a 6-12th
> grader would have such a thing, or even know where to find one.  *I* have a lot of
> junk in the garage, and even some synchronous motors, but not one that could directly
> be connected to the mains.
>
> an AC powered rotary dial electric clock, perhaps? (assuming it's not a wall wart
> powering a "quartz movement".)