Energy v cost, do people really not know the difference?

[JohnW2]

Are you really suggesting, that you could find no easy way to source 50Hz from the mains, despite SMPSU's?

It would be exceptionally easy but, as has been said, in the name of 'safety' would probably require a (otherwise unnecessary) 50 Hz transformer or an opto-isolator, both of which would represent 'a cost'.

 

[JohnW2]

Most, work using a large, very heavy, mains, to high voltage transformer, followed by a rectifier.

That has, indeed, been the case with every microwave oven that I've dissected. However, a very brief conversation with Mr Google indicates that there are plenty of SMPSUs for microwave oven magnetrons out there.

 

[Harry Bloomfield]

It would be exceptionally easy but, as has been said, in the name of 'safety' would probably require a (otherwise unnecessary) 50 Hz transformer or an opto-isolator, both of which would represent 'a cost'.

You can pick up the mains signal, from the air, on just a bit of wire..

 

[endecotp]

Are you really suggesting, that you could find no easy way to source 50Hz from the mains, despite SMPSU's?

Reasonably easy - an opto-coupler - but not cheaper than a 32 kHz crystal.

 

[JohnW2]

You can pick up the mains signal, from the air, on just a bit of wire..

One can, and I almost mentioned that possibility, but do you really believe it would be reliable enough? Don't forget that, to be accurate, it has to 'see' every single cycle of the mains every day.

 

[Harry Bloomfield]

One can, and I almost mentioned that possibility, but do you really believe it would be reliable enough? Don't forget that, to be accurate, it has to 'see' every single cycle of the mains every day.

Have you ever tried avoiding mains pickup, it's not easy.

 

[JohnW2]

Have you ever tried avoiding mains pickup, it's not easy.

Indeed - in fact, usually impossible. However, I've never been in the position of having something which needed to see, and count, every cycle, every day, so I just don't know how well that would work if one were relying on 'mains pickup'.

There would also presumably be the need for some 'filtering', which would involve additional complexity and cost, otherwise what was being 'picked up' could be due to nearby transmitting equipment - maybe even WiFi or that due to new-fangled technologies - maybe the clock would suddenly go fast when eric turned on his bedroom light

I also wonder how well your proposal would work with a situation as in my house, where there are three (obviously out-of-phase) phases that could be 'picked up'?accurate enough for a cooker or microwave

I suppose what it comes down to is that I think you are trying to be 'unnecessarily clever'. A cheap quartz crystal is plenty accurate enough for a cooker or microwave