a 45rpm strobe disc that is accurate under 50Hz lighting. The closest you can get is 45.112rpm
Fascinating!! So would you offset the crystal to get it accurate??
I have recently learned that most discs are actually cut at 45.11, and not 45.00 - because the cutting lathes were mostly driven from synchronous motors.
So the 'error' in the strobe disc turns out to not be an error at all, because you dont want 45.00.
Quartz turntables that do exactly 45.00 are apparently wrong.
will the disks work under a compact florescent light?
and are the little dots supposed look like they aren't moving, or should they be blurry?
Generally CFL lamps don't work - they don't flash at mains frequency, they have their own oscillators inside.
The blurriness of the dots depends on the 'quality' of the strobe waveform. My DIY version gives significantly less blurry dots than a mains-powered neon or LED lamp, because the current pulse to my LED is very short.
So how do i tell if my turntable is going at the right speed?
The strobe ring appears to stand still, as if it were not rotating at all.