> On the consumer side, your microwave, coffee machine and even bedside clock will
I'd be very surprised. It's cheaper to build in a 32.768kHz crystal for timekeeping than try to access the grid frequency from the isolated low-voltage circuit.
I'd be very surprised. It's cheaper to build in a 32.768kHz crystal for timekeeping than try to access the grid frequency from the isolated low-voltage circuit.
Those products don't use isolated power supplies --- normally they use a capacitive dropper. A high-value resistor to an IC pin is sufficient to drive the clock counter, and a resistor is definitely cheaper than a crystal.
A similar event happened in Europe a year ago (also due to problems in former Yugoslavia) and all electric clocks in my house (microwave, oven, alarm clocks) went out of sync temporarily. I was just as surprised as you.
Basically, it's exactly the devices that lose track of time in case of a power outage, and that you need to manually adjust for daylight savings time, that are synchronized to the grid. Devices that use a battery (such as laptops, mobile phones, and CMOS clocks in PCs) must necessarily use some other means.
It doesn't seem to be much correlated with price either: my alarm clock cost over $100 and it was still affected. Surely at that price point they could have afforded a crystal oscillator in the design, if they wanted to, but it seems this just isn't typically done.
It might even project the moon phase on the ceiling.
The idea is that it wakes you up gently by flooding the room with light resembling a natural sunrise. One reason that it might be expensive is that it needs a lot of high luminance hue shifting LEDs, and possibly I overpaid a bit (there do seem to be much cheaper competitors) but it was still a good investment because it does make my mornings a lot more pleasant.
50Hz might have temporary variations, but it's controlled so that over a longer period of time, you always get the correct number of cycles, e.g. 180000 in an hour.
This also means that going off the 50Hz power grid theoretically has better (or even perfect) long-term accuracy. Also means that if you adjusted your clock for this separation event, you'll have to adjust it back :D
That's much, much worse than a cheap digital watch from 20 years ago.
> I'd be very surprised. It's cheaper to build in a 32.768kHz crystal for timekeeping than try to access the grid frequency from the isolated low-voltage circuit.
IIRC, the grid frequency is usually more accurate. Probably because it's carefully monitored and managed by the power authorities like the OP describes. If you build a clock with its own frequency reference, than any error will accumulate and have to be monitored and managed by the user.
If not, why don't coffee machines that can start on a timer have a backup battery for their clock? That might be cheap enough too. And vital for those moments when there was a 10 second brownout which leads to your coffee not being ready in the morning...
As a European the thought wouldn't have come to me. Brownouts just don't happen (see this 0.5% frequency dip making headlines), and a blackout is a once-a-decade event for any given house (probably even less frequent than that).
So your answer is probably that demand for that feature is far from universal, and a coffee machine is much lower stakes than for example an alarm clock.
This. Can't put the coffee maker on an UPS though. Or not on a cost effective UPS.
> So your answer is probably that demand for that feature is far from universal, and a coffee machine is much lower stakes than for example an alarm clock.
Actually for the alarm clock i'm just going to be late. Not having coffee hurts much more!