5 ms·

Whoa, ever since learning about this, I randomly tell people about this. Noone ever seems to understand my fascination with this distributed grid of spinny thin

Whoa, ever since learning about this, I randomly tell people about this. Noone ever seems to understand my fascination with this distributed grid of spinny things interacting. I'm glad there's at least two of us ;)

HPsquared 3y ago
Before quartz oscillators, clocks would use the grid as their time reference. It can be done mechanically via a small synchronous motor and some gears. I'm not sure if it's still the case today, but the grid frequency used to be managed through the night so those clocks were most accurate in the morning (for peoples' alarm clocks)
- michaelt 3y ago
  > Before quartz oscillators Some systems still use grid frequency for timekeeping. If you own a mechanical rotary timeswitch, it's got a synchronous motor spinning 50 or 60 times a second, then a series of gears, gearing it down to 1 rotation per day.
  - isoprophlex 3y ago
    Yeah. Some years back there was a structural underfreq event for a couple of weeks on the European grid. My microwave phased out of time by several minutes, and then phased back. Was fun to observe. https://www.theguardian.com/world/2018/mar/08/european-clocks-lose-six-minutes-dispute-power-electricity-grid https://www.theguardian.com/world/2018/mar/08/european-clock...
    - cesarb 3y ago
      Interestingly, my country (Brazil) doesn't seem to regulate the grid frequency for use as a time reference, at least as far as I could find. So if this happened here, and if the microwave used the grid frequency for its clock, the clock would stay wrong.
  - throwaway173738 3y ago
    A switch such as would be present in an older clothes dryer or washing machine. The newer ones use electronically controlled relays but I could see the designers skipping the quartz oscillator because the time difference comes out in the wash.
    - tnorthcutt 3y ago
      comes out in the wash Very, very well done
- bri3d 3y ago
  This isn't just a "before quartz oscillators" thing; it's still in extremely widespread use today since quartz oscillators still cost some fraction more than $0. And, it's not always mechanical, there are a lot of all-in-one timekeeping/clock chips that use AC as the reference frequency for their internal oscillator/PLL. Almost all cheap / "simple" consumer mains appliances, including non-"smart" microwaves, ovens, alarm clocks, etc. still use mains frequency as their time reference. Due to the growing complexity of power grids and in Europe, international power-grid politics and infighting, the grid frequency is becoming less stable and you see these devices fluctuate badly more often than they used to. https://hackaday.com/2018/03/09/europe-loses-six-minutes-due-to-sagging-frequency-and-international-politics/ https://hackaday.com/2018/03/09/europe-loses-six-minutes-due...
  - kensey 3y ago
    I have one of those little “binary clocks” (it technically displays in BCD, but it’s still “binary”, right?). When I first set it up, it was running really fast —- like it was gaining hours over the course of a day. Turns out it had a button combo for “switch between 50Hz and 60Hz mode” that was similar to its combo for (what I thought I was setting) “switch between 12- and 24-hour mode”. (I think the 12/24 switch was “hold the hour button down while plugging in” and the 50/60 switch was “hold both buttons down while plugging in”.)
  - bsder 3y ago
    > Almost all cheap / "simple" consumer mains appliances, including non-"smart" microwaves, ovens, alarm clocks, etc. still use mains frequency as their time reference. I find this incredibly hard to believe. Crystals are incredibly cheap and waaaaaay more accurate than anything that the grid does. If you're not an actual motor, sensing the grid is both an engineering challenge and a non-trivial expense.
    - AdamH12113 3y ago
      To my understanding, the grid is managed to have a fixed number of cycles per day, which would make it perfectly accurate. A cheap crystal can easily lose a few seconds per day. And given how hard it is to keep 60 Hz noise out of circuits, I can’t imagine the sensing would be difficult.
jupp0r 3y ago
There is a whole world of nerds who do this in their job every day. They are fun people.
yannyu 3y ago
I studied electrical engineering, but power engineering isn't a course that I took. The most enlightening quote I've heard about this was a response to a question: "What happens when I turn on an electric device in my house?" "A turbine in a power plant spins more slowly for just a moment."

HPsquared 3y ago

Before quartz oscillators, clocks would use the grid as their time reference. It can be done mechanically via a small synchronous motor and some gears. I'm not sure if it's still the case today, but the grid frequency used to be managed through the night so those clocks were most accurate in the morning (for peoples' alarm clocks)

michaelt 3y ago
> Before quartz oscillators Some systems still use grid frequency for timekeeping. If you own a mechanical rotary timeswitch, it's got a synchronous motor spinning 50 or 60 times a second, then a series of gears, gearing it down to 1 rotation per day.
- isoprophlex 3y ago
  Yeah. Some years back there was a structural underfreq event for a couple of weeks on the European grid. My microwave phased out of time by several minutes, and then phased back. Was fun to observe. https://www.theguardian.com/world/2018/mar/08/european-clocks-lose-six-minutes-dispute-power-electricity-grid https://www.theguardian.com/world/2018/mar/08/european-clock...
  - cesarb 3y ago
    Interestingly, my country (Brazil) doesn't seem to regulate the grid frequency for use as a time reference, at least as far as I could find. So if this happened here, and if the microwave used the grid frequency for its clock, the clock would stay wrong.
- throwaway173738 3y ago
  A switch such as would be present in an older clothes dryer or washing machine. The newer ones use electronically controlled relays but I could see the designers skipping the quartz oscillator because the time difference comes out in the wash.
  - tnorthcutt 3y ago
    comes out in the wash Very, very well done
bri3d 3y ago
This isn't just a "before quartz oscillators" thing; it's still in extremely widespread use today since quartz oscillators still cost some fraction more than $0. And, it's not always mechanical, there are a lot of all-in-one timekeeping/clock chips that use AC as the reference frequency for their internal oscillator/PLL. Almost all cheap / "simple" consumer mains appliances, including non-"smart" microwaves, ovens, alarm clocks, etc. still use mains frequency as their time reference. Due to the growing complexity of power grids and in Europe, international power-grid politics and infighting, the grid frequency is becoming less stable and you see these devices fluctuate badly more often than they used to. https://hackaday.com/2018/03/09/europe-loses-six-minutes-due-to-sagging-frequency-and-international-politics/ https://hackaday.com/2018/03/09/europe-loses-six-minutes-due...
- kensey 3y ago
  I have one of those little “binary clocks” (it technically displays in BCD, but it’s still “binary”, right?). When I first set it up, it was running really fast —- like it was gaining hours over the course of a day. Turns out it had a button combo for “switch between 50Hz and 60Hz mode” that was similar to its combo for (what I thought I was setting) “switch between 12- and 24-hour mode”. (I think the 12/24 switch was “hold the hour button down while plugging in” and the 50/60 switch was “hold both buttons down while plugging in”.)
- bsder 3y ago
  > Almost all cheap / "simple" consumer mains appliances, including non-"smart" microwaves, ovens, alarm clocks, etc. still use mains frequency as their time reference. I find this incredibly hard to believe. Crystals are incredibly cheap and waaaaaay more accurate than anything that the grid does. If you're not an actual motor, sensing the grid is both an engineering challenge and a non-trivial expense.
  - AdamH12113 3y ago
    To my understanding, the grid is managed to have a fixed number of cycles per day, which would make it perfectly accurate. A cheap crystal can easily lose a few seconds per day. And given how hard it is to keep 60 Hz noise out of circuits, I can’t imagine the sensing would be difficult.

jupp0r 3y ago

There is a whole world of nerds who do this in their job every day. They are fun people.

yannyu 3y ago

I studied electrical engineering, but power engineering isn't a course that I took. The most enlightening quote I've heard about this was a response to a question: "What happens when I turn on an electric device in my house?" "A turbine in a power plant spins more slowly for just a moment."