4 ms·

Where does my car get the time from? It drifts and changes every time I start it up. Every 3 months I have to change it manually by 10ish minutes or more, but i

Where does my car get the time from? It drifts and changes every time I start it up. Every 3 months I have to change it manually by 10ish minutes or more, but it’s inconsistent

willis936 3y ago
It sounds like it gets the time from you.
- fuzzfactor 3y ago
  Laurens Hammond invented the synchronous electric motor once A/C domestic voltage had proliferated enough as an alternative to the original D/C electrification first established by Edison. This made it possible for the first time to build clocks based on the stable frequency of the incoming A/C supply voltage, much more reliably than those based on the incoming line voltage, which varies quite a bit whether it is A/C or D/C. This put him on the map as a manufacturer when he went forward to build Hammond clocks commercially. Years later his engineers encouraged him to consider developing an electric church organ, which would be possible to remain in tune regardless of variations in line voltage themselves. Hammond was not musically inclined but he did it anyway. Right up there with the Great Men in the most legendary way. http://thehammondorganstory.com/ http://thehammondorganstory.com/ By the time the 1960's came around, almost all new American vehicles were recognized as modern Space Age conveniences, and a factory clock (mechanical analog, naturally) had become almost a universal standard accessory beyond the most budget price points. There were a couple drawbacks to the factory clocks, they had to be connected to the car battery at all times to keep running, they didn't drain the battery very much at all but still would eventually deaden it if undriven, way worse than no clock. And they depended on the incoming voltage which determined the internal clock motor speed to begin with. Different automotive electrical systems and batteries themselves do vary perhaps 10 percent about a nominal design voltage of 12 VDC. There is no stable A/C in the car that a synchronous motor would need to run on[0]. These now-vintage clocks were self-correcting. You correct them yourself. Actually the same twisting of the knob to move the hands of the clock, which was familiar from earlier non-correcting clocks simply did the job. So they were somewhat backward-compatible. Only the Space Age units had smart enough mechanical ability to take into account how much and in which direction you moved the hands, and adjusted the previous running speed accordingly. If the clock was not very close to correct time when you adjusted it, it would take repeated adjustments over a number of days or weeks to get it to very realistic speed. All it really did was successive approximation. You had to supply your own natural intelligence. Even at the time lots of drivers never knew this, and there was widespread disappointment over the wildly inaccurate clocks "which were OK when new but went downhill 'through time'". They only added maybe a dollar to your car payment but that was very expensive compared to a highly reliable cheap household clock at the time. When you think about it, today lots of drivers are not quite up to par when it comes to engaging the amount of natural intelligence that would be needed in many other ways besides timekeeping. [0] The electrical "vibrator" which provided switch-mode 12VAC which could be stepped up by a transformer to supply much higher voltage to power vacuum tube radios still produced a variable A/C voltage & frequency, dependent on the underlying D/C supply voltage.
  - linkjuice4all 3y ago
    The clock in my 1967 Mercury has an interesting mechanism. It's a fully mechanical wound spring clock with a self-winding mechanism. When the spring unwinds it closes a circuit on an electromagnet that quickly rewinds the clock spring. Every couple of hours or so you'll hear the click from it rewinding on its own. Unfortunately there's nothing to prevent it from running down the battery and they often need to be replaced due to burn out when the voltage gets low. Essentially the rewinder doesn't have enough voltage to actually wind the clock and the circuit stays closed.
    - fuzzfactor 3y ago
      Nothing like a '60's Mercury when they were still building them more carefully than the corresponding mainstream Ford-badged models. >Well if I had money >Tell you what I'd do >I'd go downtown and buy a Mercury or two Mercury Blues: https://www.youtube.com/watch?v=QsTfCITzISM https://www.youtube.com/watch?v=QsTfCITzISM I could really use a Mercury or two about now myself.
lm28469 3y ago
Depends on the car model. Some can use GPS or radio time signals: https://en.wikipedia.org/wiki/Time_signal https://en.wikipedia.org/wiki/Time_signal
spelunker 3y ago
I have the same problem! It takes months, but eventually the clock in my car is minutes behind. I think currently it's about 4 minutes behind.
SAI_Peregrinus 3y ago
Probably just a local quartz oscillator, like a cheap wristwatch but embedded into the car. That'll drift with temperature, vibration, humidity, and some other factors, but it's cheap and just relies on the user to occasionally set it. Fancier systems can use radio time or GNSS (more likely if the car has built in navigation), but that's probably not happening if you regularly set the time!
- CableNinja 3y ago
  Correct. Oscillators are subject to drift through a number of means, and they all have ridiculous effects too. https://news.ycombinator.com/item?id=37613523 https://news.ycombinator.com/item?id=37613523
  - jrockway 3y ago
    Temperature is the largest factor. Things like a DS3231[1] do really well compared to a basic non-compensated oscillator. I have been running some long-term experiments on a few that I have around and with some tuning got them to less than a second loss per year. But, they are super expensive compared to the basic ones (almost $5 each in quantity), so they aren't going to end up in your car where a 3 cent chip is possible to use instead. (I don't know what 5G / LTE chips cost these days, but if they're putting one in your car anyway, then they can probably get the time from that. But choose not to.) [1] https://www.analog.com/media/en/technical-documentation/data-sheets/DS3231.pdf https://www.analog.com/media/en/technical-documentation/data... Most interesting to me in all of my time experiments is looking at my clock frequency over time vs. the temperature. (NTP daemons aim to calculate your actual clock frequency; then they know how far off your internal time is from actual time.) You don't even need a temperature sensor, the clock rate is a perfect analogue.
    - lazide 3y ago
      Voltage issues can also be a big problem, and cars have notoriously dirty electrical.
incanus77 3y ago
What really gets me is when the gauge cluster clock and the radio clock differ. Just a wonderful metaphor for the modern car.
CableNinja 3y ago
Here, have a rabbithole. https://news.ycombinator.com/item?id=37613523 https://news.ycombinator.com/item?id=37613523
paxys 3y ago
I recently rented a $65000 luxury car and it didn't even have built-in daylight savings adjustment. Owners have to dig into settings and fix it themselves twice a year. Cars are so far behind on basic software it is crazy.
- ipython 3y ago
  Oh, it gets better. I used to get reminders in the mail to take my luxury car into the dealership for "service" to adjust the clock twice a year. Or I could ... you know, just press a few buttons for free. The trouble with all the modern cars that have synchronized clocks is that, well, you've already put in an LTE SIM card, so why not send up some telemetry at the same time? And here we are, with cars that are surveillance devices with four wheels.
  - reaperman 3y ago
    A simple GPS receiver could also provide the time. But I agree with your rant overall.
- AdamH12113 3y ago
  DST policies vary by country and (US) state. The US DST schedule can be changed, and has been — twice in the last 50 years. There are proposals to do so again, both nationally and within states. Implementing automatic DST adjustment puts you on the hook for software updates forever. It’s much easier to just let people change the time manually when they need to, like they do with other appliances. IMHO, the real failure is when devices make it hard to figure out how to change the time.
  - notatoad 3y ago
    yeah, DST schedules change frequently enough that within the lifetime of most automobiles, at least some of them will be in use in some location where up-to-date timezone database doesn't match the timezone database in the car's software. so the manufacturer gets to choose between making people apply DST changes manually twice a year, which most people understand and are used to doing for various things, or changing over for DST automatically but being wrong sometimes, which most people won't understand and will complain about.

Where does my car get the time from? It drifts and changes every time I start it up. Every 3 months I have to change it manually by 10ish minutes or more, but it’s inconsistent

willis936 3y ago

It sounds like it gets the time from you.

fuzzfactor 3y ago
Laurens Hammond invented the synchronous electric motor once A/C domestic voltage had proliferated enough as an alternative to the original D/C electrification first established by Edison. This made it possible for the first time to build clocks based on the stable frequency of the incoming A/C supply voltage, much more reliably than those based on the incoming line voltage, which varies quite a bit whether it is A/C or D/C. This put him on the map as a manufacturer when he went forward to build Hammond clocks commercially. Years later his engineers encouraged him to consider developing an electric church organ, which would be possible to remain in tune regardless of variations in line voltage themselves. Hammond was not musically inclined but he did it anyway. Right up there with the Great Men in the most legendary way. http://thehammondorganstory.com/ http://thehammondorganstory.com/ By the time the 1960's came around, almost all new American vehicles were recognized as modern Space Age conveniences, and a factory clock (mechanical analog, naturally) had become almost a universal standard accessory beyond the most budget price points. There were a couple drawbacks to the factory clocks, they had to be connected to the car battery at all times to keep running, they didn't drain the battery very much at all but still would eventually deaden it if undriven, way worse than no clock. And they depended on the incoming voltage which determined the internal clock motor speed to begin with. Different automotive electrical systems and batteries themselves do vary perhaps 10 percent about a nominal design voltage of 12 VDC. There is no stable A/C in the car that a synchronous motor would need to run on[0]. These now-vintage clocks were self-correcting. You correct them yourself. Actually the same twisting of the knob to move the hands of the clock, which was familiar from earlier non-correcting clocks simply did the job. So they were somewhat backward-compatible. Only the Space Age units had smart enough mechanical ability to take into account how much and in which direction you moved the hands, and adjusted the previous running speed accordingly. If the clock was not very close to correct time when you adjusted it, it would take repeated adjustments over a number of days or weeks to get it to very realistic speed. All it really did was successive approximation. You had to supply your own natural intelligence. Even at the time lots of drivers never knew this, and there was widespread disappointment over the wildly inaccurate clocks "which were OK when new but went downhill 'through time'". They only added maybe a dollar to your car payment but that was very expensive compared to a highly reliable cheap household clock at the time. When you think about it, today lots of drivers are not quite up to par when it comes to engaging the amount of natural intelligence that would be needed in many other ways besides timekeeping. [0] The electrical "vibrator" which provided switch-mode 12VAC which could be stepped up by a transformer to supply much higher voltage to power vacuum tube radios still produced a variable A/C voltage & frequency, dependent on the underlying D/C supply voltage.
- linkjuice4all 3y ago
  The clock in my 1967 Mercury has an interesting mechanism. It's a fully mechanical wound spring clock with a self-winding mechanism. When the spring unwinds it closes a circuit on an electromagnet that quickly rewinds the clock spring. Every couple of hours or so you'll hear the click from it rewinding on its own. Unfortunately there's nothing to prevent it from running down the battery and they often need to be replaced due to burn out when the voltage gets low. Essentially the rewinder doesn't have enough voltage to actually wind the clock and the circuit stays closed.
  - fuzzfactor 3y ago
    Nothing like a '60's Mercury when they were still building them more carefully than the corresponding mainstream Ford-badged models. >Well if I had money >Tell you what I'd do >I'd go downtown and buy a Mercury or two Mercury Blues: https://www.youtube.com/watch?v=QsTfCITzISM https://www.youtube.com/watch?v=QsTfCITzISM I could really use a Mercury or two about now myself.

lm28469 3y ago

Depends on the car model. Some can use GPS or radio time signals: https://en.wikipedia.org/wiki/Time_signal https://en.wikipedia.org/wiki/Time_signal

spelunker 3y ago

I have the same problem! It takes months, but eventually the clock in my car is minutes behind. I think currently it's about 4 minutes behind.

SAI_Peregrinus 3y ago

Probably just a local quartz oscillator, like a cheap wristwatch but embedded into the car. That'll drift with temperature, vibration, humidity, and some other factors, but it's cheap and just relies on the user to occasionally set it. Fancier systems can use radio time or GNSS (more likely if the car has built in navigation), but that's probably not happening if you regularly set the time!

CableNinja 3y ago
Correct. Oscillators are subject to drift through a number of means, and they all have ridiculous effects too. https://news.ycombinator.com/item?id=37613523 https://news.ycombinator.com/item?id=37613523
- jrockway 3y ago
  Temperature is the largest factor. Things like a DS3231[1] do really well compared to a basic non-compensated oscillator. I have been running some long-term experiments on a few that I have around and with some tuning got them to less than a second loss per year. But, they are super expensive compared to the basic ones (almost $5 each in quantity), so they aren't going to end up in your car where a 3 cent chip is possible to use instead. (I don't know what 5G / LTE chips cost these days, but if they're putting one in your car anyway, then they can probably get the time from that. But choose not to.) [1] https://www.analog.com/media/en/technical-documentation/data-sheets/DS3231.pdf https://www.analog.com/media/en/technical-documentation/data... Most interesting to me in all of my time experiments is looking at my clock frequency over time vs. the temperature. (NTP daemons aim to calculate your actual clock frequency; then they know how far off your internal time is from actual time.) You don't even need a temperature sensor, the clock rate is a perfect analogue.
  - lazide 3y ago
    Voltage issues can also be a big problem, and cars have notoriously dirty electrical.

incanus77 3y ago

What really gets me is when the gauge cluster clock and the radio clock differ. Just a wonderful metaphor for the modern car.

CableNinja 3y ago

Here, have a rabbithole. https://news.ycombinator.com/item?id=37613523 https://news.ycombinator.com/item?id=37613523

paxys 3y ago

I recently rented a $65000 luxury car and it didn't even have built-in daylight savings adjustment. Owners have to dig into settings and fix it themselves twice a year. Cars are so far behind on basic software it is crazy.

ipython 3y ago
Oh, it gets better. I used to get reminders in the mail to take my luxury car into the dealership for "service" to adjust the clock twice a year. Or I could ... you know, just press a few buttons for free. The trouble with all the modern cars that have synchronized clocks is that, well, you've already put in an LTE SIM card, so why not send up some telemetry at the same time? And here we are, with cars that are surveillance devices with four wheels.
- reaperman 3y ago
  A simple GPS receiver could also provide the time. But I agree with your rant overall.
AdamH12113 3y ago
DST policies vary by country and (US) state. The US DST schedule can be changed, and has been — twice in the last 50 years. There are proposals to do so again, both nationally and within states. Implementing automatic DST adjustment puts you on the hook for software updates forever. It’s much easier to just let people change the time manually when they need to, like they do with other appliances. IMHO, the real failure is when devices make it hard to figure out how to change the time.
- notatoad 3y ago
  yeah, DST schedules change frequently enough that within the lifetime of most automobiles, at least some of them will be in use in some location where up-to-date timezone database doesn't match the timezone database in the car's software. so the manufacturer gets to choose between making people apply DST changes manually twice a year, which most people understand and are used to doing for various things, or changing over for DST automatically but being wrong sometimes, which most people won't understand and will complain about.