Digital clock

[plcboy]

HI
I have two digital wall mounted clock that both do not indicate exact time .
both retard the time . I did open one of them to examine if there is a adjustment for advance and retard the time but nothing at all. If anybody have knowledge in digital clock please let me know what to check. Thanks a lot

 

[Reloadron]

There are a few ways that a simple digital clock can derive time. The simple method is to have the clock use the 50 or 60 Hz. line frequency (you don't mention your location) in the case of mains powered clocks. The other is the clock has an internal oscillator that is divided down. Both these methods generally divide down to a 1 second pulse for the clock. Clocks that rely on mains power frequency will lose time if the mains frequency they are designed for is low and gain time if the mains frequency is high. Clocks like this have no adjustment in most cases. Clocks that have an internal oscillator generally do not have adjustments either.

Your question really depends on the type clock you have. Since you have two clocks with identical issues of running slow I would venture they rely on power mains frequency and wherever you are located the frequency is low. That would be my guess. You don't mention how much time over a period they lose?

Ron

 

[plcboy]

HI RON
Both clocks are battery operated and in regards to how many minutes lost in 24 hours not been measured yet but I will let you know. Thanks

 

[Reloadron]

Battery operated clocks have their own on-board crystal oscillator they use as a time base. Generally they use a 32,768 Hz. frequency that is divided down to 1 Hz for 1 second ticks. Even if the clock had an adjustment to tweak the oscillator frequency it would be difficult to do without some expensive test equipment like a good frequency counter. It would be interesting to get an idea of the time loss over a period, so please do post back.

Ron

 

[plcboy]

I have synchronized the clock with my laptop, let you know after 24 hours exactly how many minutes lost.Thanks again

 

[Boncuk]

There are a few ways that a simple digital clock can derive time. The simple method is to have the clock use the 50 or 60 Hz. line frequency (you don't mention your location) in the case of mains powered clocks. The other is the clock has an internal oscillator that is divided down. Both these methods generally divide down to a 1 second pulse for the clock. Clocks that rely on mains power frequency will lose time if the mains frequency they are designed for is low and gain time if the mains frequency is high. Clocks like this have no adjustment in most cases.

Ron

Hi Ron,

just for your information: mains frequency clocks are controlled by the country's master clock which is based on a ruby diamond (nuclear clock) with an accuracy of 0.3 seconds within 1,000 years.

If mains frequency has to be increased for proper grid function it will be decreased for the same time period and decreased frequency to compensate time errors.

Generally mains controlled clocks are the most precise clocks you can get.

Regards

Hans

 

[Reloadron]

Hi Ya Hans,

Oh generally I would agree and am familiar with the grid and how they maintain the frequency here in the US and the compensation applied. Actually I was thinking cesium for atomic clock but here nor there. My experience with mains frequency is that it is generally accurate but here in the US they are screwing with it, take a lookie at this thread I had going awhile back. Now back when I was living in Italy the grid sucked as power came and went and the voltage was anywhere between 205 and 220. We had an old analog large face meter and we enjoyed watching it bounce around. It was funny. Hell you could watch voltage fluctuate in an incandescent lamp. The frequency was almost always low and the 50 Hz. varied between as low as 45 and averaged about 49 Hz, seldom being 50 Hz.

So while I would generally agree:

Generally mains controlled clocks are the most precise clocks you can get.

I figure that it is a function of where you are on the planet.

Just my take on it.....
Ron

 

[Sceadwian]

And over what period of time you're averaging Reloadron, for accuracy bellow 1hz the native clock is important, and the power grid averages every single cycle over hours if not days of time. You'd need a meter than can provide a calibrated .01 hertz or so accuracy to investigate power line frequency. Local voltage fluctuations are perfectly normal, it's not funny at all, I think the typical voltage allowance is 10%. Frequency much lower.

 

[crutschow]

Battery operated clocks have their own on-board crystal oscillator they use as a time base. Generally they use a 32,768 Hz. frequency that is divided down to 1 Hz for 1 second ticks. Even if the clock had an adjustment to tweak the oscillator frequency it would be difficult to do without some expensive test equipment like a good frequency counter. It would be interesting to get an idea of the time loss over a period, so please do post back.

I adjusted the frequency of my digital wrist-watch by slightly changing the setting on the trimmer cap (there was a small adjusting screw on the watch circuit board which I assume was a cap) and then observing the time over several days to see the change. By doing this a few times I was able to get an accuracy of about 1s/month.

 

[KeepItSimpleStupid]

www.clockparts.com has some cheap movements.

 

[Boncuk]

Hi Carl,

in Germany we have a transmitting station which transmits the nuclear master time within a radius of 2,500km. The name of the station is DCF77. (It transmits on 76.5KHz). You can see the huge antenna array when travelling to Frankfurt/Main. Exact location is Mainflingen.

Even kitchen clocks have a built-in DCF77 receiver and synchronize themselves as soon as a battery is connected.

It's funny looking at an analog clock when time is changed from summer to winter time. The clocks make good one hour within a few seconds.

Cheers

Hans

 

[Reloadron]

And over what period of time you're averaging Reloadron, for accuracy bellow 1hz the native clock is important, and the power grid averages every single cycle over hours if not days of time. You'd need a meter than can provide a calibrated .01 hertz or so accuracy to investigate power line frequency. Local voltage fluctuations are perfectly normal, it's not funny at all, I think the typical voltage allowance is 10%. Frequency much lower.

I understand how the US power grids work (actually the US has three power grids). Texas is unto a grid all its own with an east and west grid for a total of three US power grids. Corrections to the grid are done on a periodic basis which could be days or weeks.

When I answered the OPs question initially I was not aware if his clocks were deriving their accuracy from mains power or an internal oscillator and if mains frequency I had no clue as to the country of origin. While I understand the uncertainty of US Mains Power Frequency I have no clue as to the uncertainty of the mains frequencies around the world? I can only speak somewhat for Italy where I lived for 3 years and mains power frequency was nothing to write home about.

As to measuring US Power Mains Frequency. Resolving 60 hertz down to .001 ( 1 mHZ) is not that difficult at all. At home I use an old HP 5334B Frequency Counter with the 10 MHz TCXO oven option(5 parts in 10 ^ -10). While an older counter it will measure 60 Hz with .001 Hz resolution to an uncertainty of +/- about 30 uHZ. If I want better I can use an external time base. Anyway measuring 60 Hz mains power with .01 Hz resolution and doing it accurately really does not require much. Measuring the period for .001 Hz resolution would require a gate time of 100 seconds so a ten period average would be about 1,000 seconds roughly 17 min.

Back to US mains uncertainty. Yes, it is accurate but there seems to be change in the air. Remember those periodic corrections? Earlier in this thread I linked to this forum thread. Which links to proposed changes to the US power grids and how they are maintained as to frequency. For those unaware this is what is going on with the US power grids as to frequency.

All of this being a moot point as when the OP returned they stated they had battery powered clocks which brings us to crutschow's watch. The idea at this point will be to see how much the clocks deviate (drift) over specified periods of time.

<EDIT> @ Hans:

It's funny looking at an analog clock when time is changed from summer to winter time. The clocks make good one hour within a few seconds.

Hans, isn't it Spring Ahead transitioning from winter to summer and Fall Back going from summer to winter? So when an atomic synchronized clock goes from winter to summer it would advance an hour real fast. When they go from summer to winter what does it do? Advance a quick 11 hours? That has to be amusing to watch. We have them here in the US but I have never bothered to get one. </EDIT>

Ron

 

[Mr RB]

On the bottom half of this page;
https://www.romanblack.com/onesec/High_Acc_Timing.htm

there are 3 methods of syncing a PIC microcontroller to the mains frequency, one in particular the "pulse counting loop" allows the same average frequency as the mains, but with a much more stable short term frequency derived from the PIC xtal.

So you get the long term time from the AC mains but short term it will handle loss of mains or dirty mains waveform with no effect on the timekeeping.

 

[plcboy]

HI guys
I have measured only one clock with my laptop clock and after exactly 7 days it has been retarted exactly( 25) seconds. IS there any solution or it is nature of the beast as bought cheap. Thanks for the input.

 

[alec_t]

it is nature of the beast as bought cheap

That sums it up. I doubt there is any easily accessible component inside which could be adjusted simply. As the clock oscillator frequency is clearly too low IMHO the only solution would be to replace the crystal with a better quality one of good accuracy. That might cost you more than the price you paid for the clock! (Had the oscillator frequency been too high you might have been able to connect a small capacitor to the crystal to lower the frequency).

 

[Reloadron]

Unless there is an adjustment, I agree it's just the nature of the beast.

Ron

 

[carbonzit]

One question (this prompted by reading your earlier thread, Reload-Ron): Who still uses electric clocks? I mean the old-fashioned analog hands-spin-around type? (I actually have one of those, in the remains of an old Japanese clock radio I keep around just for retro purposes)? Or the not-quite-as-old-fashioned type where the numbers are on plastic cards on spindles (that look "digital" but are really analog, turned by a slow-running clock motor)?

Or do people still have plug-in digital clocks (most likely LED)?

 

[Reloadron]

One question (this prompted by reading your earlier thread, Reload-Ron): Who still uses electric clocks? I mean the old-fashioned analog hands-spin-around type? (I actually have one of those, in the remains of an old Japanese clock radio I keep around just for retro purposes)? Or the not-quite-as-old-fashioned type where the numbers are on plastic cards on spindles (that look "digital" but are really analog, turned by a slow-running clock motor)?

Or do people still have plug-in digital clocks (most likely LED)?

Good question. I don't think we have had an AC mains powered wall clock in the house for years but they apparently are still pretty widely used. I know for example McMaster Carr Supply still sells them. The other clocks you mention were pretty cool. That "digital look".

Ron