Geekzone: technology news, blogs, forums
Guest
Welcome Guest.
You haven't logged in yet. If you don't have an account you can register now.
View this topic in a long page with up to 500 replies per page Create new topic
1 | 2 
Hmm, what to write...
990 posts

Ultimate Geek
+1 received by user: 499

Trusted
Lifetime subscriber

  Reply # 1450120 14-Dec-2015 13:34
Send private message

I use a Sony projector clock that projects the time on the ceiling. It is very geeky  (Yep battery backup as well)




Matthew


21389 posts

Uber Geek
+1 received by user: 4336

Trusted
Subscriber

  Reply # 1450121 14-Dec-2015 13:35
Send private message

This has happened to me when a GSM phone was right beside a cheap alarm clock.




Richard rich.ms

gzt

10125 posts

Uber Geek
+1 received by user: 1541


  Reply # 1450137 14-Dec-2015 13:57
Send private message

mdooher:
Aredwood:
gzt: Mains frequency would never be reliable enough. The clock will use an xco and presumably a component or interface of that has failed in this instance.


Actually the mains frequency is surprisingly accurate. As every time it goes lower than 49.5Hz or higher than 50.5Hz, Transpower issue an Excursion Notice. Some months none have been issued. Which means that the mains frequency have varied by less than 1Hz for that entire month. Which means my old digital clock has no problem keeping time despite only using the mains as it's reference.


I have an old "Railway Clock" with a synchronous motor and sweep second hand. It keeps perfect time for this very reason.



In practice the analog motor design is subject to much less interference than digital.

Also in digital if a manufacturer leaves out simple xco im guessing they will skimp on everything else needed to create stability in the alternative mains freq driven design for good measure.

+1 for old analog mains clocks. Many have the added virtue of stopping when power fails and require manual restart - preserving the exact time of the first power failure. : )

Edit: format paragraph breaks

Hmm, what to write...
990 posts

Ultimate Geek
+1 received by user: 499

Trusted
Lifetime subscriber

  Reply # 1450138 14-Dec-2015 13:59
Send private message

gzt:
mdooher:
Aredwood:
gzt: Mains frequency would never be reliable enough. The clock will use an xco and presumably a component or interface of that has failed in this instance.


Actually the mains frequency is surprisingly accurate. As every time it goes lower than 49.5Hz or higher than 50.5Hz, Transpower issue an Excursion Notice. Some months none have been issued. Which means that the mains frequency have varied by less than 1Hz for that entire month. Which means my old digital clock has no problem keeping time despite only using the mains as it's reference.


I have an old "Railway Clock" with a synchronous motor and sweep second hand. It keeps perfect time for this very reason.



In practice the analog motor design is subject to much less interference than digital. Also if a manufacturer leaves out simple xco im guessing they will skimp on everything else needed to create stability in the alternative mains freq driven design for good measure.

+1 for old analog mains clocks. Many have the added virtue of stopping when power fails and require manual restart. Therefore preserving the exact time of the first power failure : ).


I LOVE that part..




Matthew


21389 posts

Uber Geek
+1 received by user: 4336

Trusted
Subscriber

  Reply # 1450145 14-Dec-2015 14:03
Send private message

gzt:
In practice the analog motor design is subject to much less interference than digital.

Also in digital if a manufacturer leaves out simple xco im guessing they will skimp on everything else needed to create stability in the alternative mains freq driven design for good measure.

+1 for old analog mains clocks. Many have the added virtue of stopping when power fails and require manual restart - preserving the exact time of the first power failure

Edit: format paragraph breaks


Mains reference for the LED bedside type clocks has been the norm for over 40 years. The only oscillator is the backup one to keep it running on the 9v battery during an outage. Its normally not very good at all




Richard rich.ms

gzt

10125 posts

Uber Geek
+1 received by user: 1541


  Reply # 1450179 14-Dec-2015 15:01
Send private message

Ok I am still amazed. Also googled for quartz led alarm. Nothing : ).

Considering a very cheap digital watch is accurate, maybe it is time for some enterprising xtal manufactuer to update the reference designs so OEM's can stamp 'Quartz' on their mains alarm clocks.

21389 posts

Uber Geek
+1 received by user: 4336

Trusted
Subscriber

  Reply # 1450188 14-Dec-2015 15:11
Send private message

Why would they when they have a more accurate time source available from the wall? Quartz watches seem to be out a few seconds a month. LED alarm clocks are locked to the power which is controled to be exact when referenced to accurate time sources. There may be a few seconds drift during the day that is caught up at night, but it will never be out over a month.




Richard rich.ms

gzt

10125 posts

Uber Geek
+1 received by user: 1541


  Reply # 1450199 14-Dec-2015 15:27
Send private message

Only because there are cases where the mains freq design fails. Other than that I agree, no reason to change.



2020 posts

Uber Geek
+1 received by user: 160


  Reply # 1461513 5-Jan-2016 11:55
Send private message

In the end I went with another $10 no brand Warehouse alarm clock (exactly the same as the Transonic model, but no longer named Transonic)
Even put in the same 9V battery and connected to the same power slot - 2 weeks later, no issues

3011 posts

Uber Geek
+1 received by user: 1153

Subscriber

  Reply # 1462018 5-Jan-2016 22:37
Send private message

gzt: Ok I am still amazed. Also googled for quartz led alarm. Nothing : ).

Considering a very cheap digital watch is accurate, maybe it is time for some enterprising xtal manufactuer to update the reference designs so OEM's can stamp 'Quartz' on their mains alarm clocks.



Problem is digital watch circuits are based on 4000 series logic ICs.  Which would be sensitive to interference. Not an issue for something that is in a metal case and runs off a battery. But would need a well designed power supply circuit and good shielding to work properly using the mains. Wouldn't trust a cheap alarm clock to have that.

Also the mains is used to multiplex the display. further simplifying the design. Those cheap mains clocks don't contain much else apart from a centre tapped transformer, the display and 1 IC that does all time related functions. 

It wouldn't be that hard to mod one of those alarm clocks to into a Nixie tube clock. Or some other custom digital clock.





1 | 2 
View this topic in a long page with up to 500 replies per page Create new topic

Twitter »

Follow us to receive Twitter updates when new discussions are posted in our forums:



Follow us to receive Twitter updates when news items and blogs are posted in our frontpage:



Follow us to receive Twitter updates when tech item prices are listed in our price comparison site:



Geekzone Live »

Try automatic live updates from Geekzone directly in your browser, without refreshing the page, with Geekzone Live now.



Are you subscribed to our RSS feed? You can download the latest headlines and summaries from our stories directly to your computer or smartphone by using a feed reader.

Alternatively, you can receive a daily email with Geekzone updates.