LED alarm clocks all lose accuracy over time

[Bill Proms]

I have 3 Intelli-Time LED alarm clocks around the house, just like the one
here:

http://www.acurite.com/clock/alarm-clock/intelli-time-digital-alarm-clock-13027a2.html

I initially bought these due to them keeping time when the power goes off
and auto resetting for DST. There is a problem, however. Each of the
clocks becomes inaccurate over time. If I set them all manually to the same
time, within a few months, each one will be off by 3-5 minutes.

So I ask, what is the problem and is there any way to repair it?

Thanks in advance,
Bill

 

[N_Cook]

I have 3 Intelli-Time LED alarm clocks around the house, just like the one
here:

http://www.acurite.com/clock/alarm-clock/intelli-time-digital-alarm-clock-13
027a2.html

I initially bought these due to them keeping time when the power goes off
and auto resetting for DST. There is a problem, however. Each of the
clocks becomes inaccurate over time. If I set them all manually to the same
time, within a few months, each one will be off by 3-5 minutes.

So I ask, what is the problem and is there any way to repair it?

Thanks in advance,
Bill

I've always put this down to hash on the mains being interpreted as extra
cycles by the clock monitoring input. The supply companies contractually
have to correct the mains frequency so an exact number of cycles per day
(50/60)x60x60x24, but at any instant can be above or below the nominal
frequency.

 

[Wolfgang Allinger]

I have 3 Intelli-Time LED alarm clocks around the house, just like
the one here: [...]
I initially bought these due to them keeping time when the power
goes off and auto resetting for DST. There is a problem, however.
Each of the clocks becomes inaccurate over time. If I set them all
manually to the same
time, within a few months, each one will be off by 3-5 minutes.

So I ask, what is the problem and is there any way to repair it?

I've always put this down to hash on the mains being interpreted as
extra cycles by the clock monitoring input. The supply companies
contractually have to correct the mains frequency so an exact number
of cycles per day (50/60)x60x60x24, but at any instant can be above or
below the nominal frequency.

Anyhow in continental Europe the 50Hz is very accurate due to the large
high voltage net, which must be synchronized to all generators in all
connected power plants.

I doubt but don`t know if GB is power connected to the continent.
So their frequency shift is possibly much larger due to less coupled
generators.

Same I think in the US where AFAIK not all powerplants are connected to
a great (one?) power net.

On load the generator/turbine set slows down a little, so frequency goes
down. On load dump they accelerate a little (less or more) depending on
the amongth of all coupled generators and the accuracy of the net
controll.

So the frequeny of 50/60Hz line varies, but in continental Europe the
50Hz varies much lesser than in all other countries.



Saludos Wolfgang

 

[Bill Proms]

Yes, there are power interruptions and surges on occasion, but the former
LED clocks I had never lost time over periods of years.

As a possible replacement, I have considered an atomic LED clock, but these
appear to be next to impossible to come by for some reason. I see LCD
atomic clocks everywhere, but most or all have to have the backlight pressed
to see the time in dim conditions.

Bill

 

[William Sommerwerck]

Barring the possibility that your powerline frequency is erratic, I'm
inclined to accept Mr Cook's explanation -- that these clocks have poor
powerline filtering, and spikes get through to trip the counter. You might
try putting a ferrite choke on the line.

The LED clock has become uncommon, if only because it doesn't lend itself to
cordless operation. I keep one in the bedroom for those occasions when I
need a loud alarm, but it's not atomically controlled.

This one looks interesting. It //claims// to always display the correct time
and adjust for DST -- which would require access to a stable time source.

http://www.amazon.com/Chaney-Instru...22?s=furniture&ie=UTF8&qid=1337435811&sr=1-22

You might look for atomic clocks using vacuum-fluorescent displays.

 

[N_Cook]

Barring the possibility that your powerline frequency is erratic, I'm
inclined to accept Mr Cook's explanation -- that these clocks have poor
powerline filtering, and spikes get through to trip the counter. You might
try putting a ferrite choke on the line.

The LED clock has become uncommon, if only because it doesn't lend itself to
cordless operation. I keep one in the bedroom for those occasions when I
need a loud alarm, but it's not atomically controlled.

This one looks interesting. It file://claims// to always display the correct time
and adjust for DST -- which would require access to a stable time source.

http://www.amazon.com/Chaney-Instruments-Acurite-Large-Display/dp/B0000C0XPQ
/ref=sr_1_22?s=furniture&ie=UTF8&qid=1337435811&sr=1-22

You might look for atomic clocks using vacuum-fluorescent displays.

This is an interesting monitor of UK mains frequency, especially when its
breaktime on commercial TV carrying football or some opium of the people
soap-opera
http://www.dynamicdemand.co.uk/grid.htm
But cycles summed over a day has to be spot on.
I want to know when the utility companies will give away "intelligent"
fridges rather than CFL , that only come on when this frequency is high

All the LED clocks I've ever had experience of always gain , never loose
time, maybe only a minute a quarter , but only gaining. So my assumption its
due to mains hash

 

[William Sommerwerck]

I once modified a vacuum fluorescent alarm clock to keep accurate

time. I opened the device, figured out what chip was used, looked at
the data sheet, and replaced the crappy RC oscillator with a 32KHz
clock crystal. When the AC power disappears, the display goes blank
and the internal 9v battery runs the clock. The problem is that the
battery drain was so high that it would kill the 9V battery in about 6
hrs. There was also no charging circuit. So, I replaced the 9V
battery with 4ea AA NiCd batteries (the clock chip would still run on
about 6VDC), and added a crude trickle charger.

The world's first clock-radio with an all-electronic digital clock -- a GE,
which I still have, 40 years after I bought it (!!!) -- used a nicad-powered
oscillator running at ~ 60Hz to keep the timer going. I don't think it ran
more than about 10 minutes.

 

[gregz]

I've always put this down to hash on the mains being interpreted as extra
cycles by the clock monitoring input. The supply companies contractually
have to correct the mains frequency so an exact number of cycles per day
(50/60)x60x60x24, but at any instant can be above or below the nominal
frequency.

I doubt if any use power line for sync. Most have battery backup. Crystals
jump frequency from time to time.

Greg

 

[William Sommerwerck]

The analog wall clocks in high skool were all wired to central time

controller. Curious as to how it worked, I dragged an oscilloscope
into the main hallway to clip onto the only accessible wires I could
find. Every 15 minutes, a sync pulse would appear on the line,
resetting the clocks to the nearest 15 minutes. Every hour, two
pulses would reset the clocks to the nearest hour. At noon and
midnight, 5 pulses would reset the clocks to midnight. Unfortunately,
gathering this intelligence required almost constant monitoring, which
attract too much attention. I was caught before I could make the
clocks run backwards. Not a great start for my first attempt at
hacking.

There's a classic "Carl and Jerry" story about this. The scholl clocks
aren't keeping good time, and -- for no obvious reason -- they run faster
when it's raining.

It turns out that the janitor's vacuum cleaner put out a lot of line noise,
and even more when it was sucking up water.

 

[Geoffrey S. Mendelson]

As a possible replacement, I have considered an atomic LED clock, but these
appear to be next to impossible to come by for some reason. I see LCD
atomic clocks everywhere, but most or all have to have the backlight pressed
to see the time in dim conditions.

It's because the US is trying to get rid of those broadcasts. With GPS they
are obsolete.

Geoff.

 

[Geoffrey S. Mendelson]

Yes, there are power interruptions and surges on occasion, but the former
LED clocks I had never lost time over periods of years.

As a possible replacement, I have considered an atomic LED clock, but these
appear to be next to impossible to come by for some reason. I see LCD
atomic clocks everywhere, but most or all have to have the backlight pressed
to see the time in dim conditions.

The real answer which has yet to be rolled out to consumers is to use NTP
(networked time protcol) self correcting clocks. They basically are are
cheap router with a single ethernet and wifi interfaces, and a display.
All of them already run NTP, it's a matter of adding the time display,
changing the setup to limit them to things needed to connect to the internet
and set the clock and repackaging them.

Figure a consumer price for the cheap ones of around $25-$30 and another
$10 for self setting GPS one.

Geoff.

 

[N_Cook]

I think I remember seeing those. Todays version will last about a
year before something blows or it falls apart. Progress?

Way back in college daze (1960's), one of my friends was trying to
devise a method of running a motor drive electric clock during power
outages. I designed a line sync blocking oscillator, that ran in sync
with the 60Hz power line frequency when that was present, but ran off
battery power at roughly 60Hz when that disappeared. To get
sufficient power to run the clock, it had two 2N3055 transistors
playing push-pull oscillator to a small power transformer. It was
big, noisy, and ugly, but worked quite well. Keeping the wet cell
battery charged was the major challenge. We were thinking of
manufacturing these, but was talked out of the idea by someone with
more marketing sense than us.

The analog wall clocks in high skool were all wired to central time
controller. Curious as to how it worked, I dragged an oscilloscope
into the main hallway to clip onto the only accessible wires I could
find. Every 15 minutes, a sync pulse would appear on the line,
resetting the clocks to the nearest 15 minutes. Every hour, two
pulses would reset the clocks to the nearest hour. At noon and
midnight, 5 pulses would reset the clocks to midnight. Unfortunately,
gathering this intelligence required almost constant monitoring, which
attract too much attention. I was caught before I could make the
clocks run backwards. Not a great start for my first attempt at
hacking.

--
Jeff Liebermann [email protected]
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

I used to "wind-up" my father by stopping the synchronus-motor clock and
with a bit of backwards pressure on the seconds hand , while turning the
power back on , the clock would go backwards

 

[Geoffrey S. Mendelson]

The 1pps output can be used to run a digital clock, but I would hate
to see the final cost.

We are talking about a clock here, something most people are to seeing
display hours and minutes. Few of them have seconds. None have 10ths,
hundreds, etc.....

While an NTP interface with wifi would do for probably 90% of the world,
the few people that don't have any internet access, would need a GPS unit.

If you can get one in a cheap cell phone these days, how much would it cost
to put in a clock? I understand that it won't give you milisecond accuracy,
but a window view that can "see" 3 or 4 satellites (or an outside antenna
would do.

However, I'd happily buy 5 or 6 of them with wifi. I'm tired of battery
run analog or even line operated digital clocks ones that are off several
minutes a week.

Yes, they have a design flaw, but I can't return them after they start
showing the time gain or loss, it takes too long to show up.

Geoff.

 

[William Sommerwerck]

Many years ago I reviewed Heath's "Most-Accurate Clock" for one of Ed Dell's
magazines. It used the Bureau of Standards' shortwave time signals. Sync was
a bit touchy (I eventually replaced the carbon calibration pots with
ceramic), but it otherwise worked very well. It even had an interface that
allowed your computer to reset its clock each time the machine restarted.

When I needed money a few years back, I sold it on eBay for something like
$400, without anyone questioning the price.

If Heath wants to come back as a kit company, it needs to design products
that have no commercial equivalents.

 

[gregz]

Many years ago I reviewed Heath's "Most-Accurate Clock" for one of Ed Dell's
magazines. It used the Bureau of Standards' shortwave time signals. Sync was
a bit touchy (I eventually replaced the carbon calibration pots with
ceramic), but it otherwise worked very well. It even had an interface that
allowed your computer to reset its clock each time the machine restarted.

When I needed money a few years back, I sold it on eBay for something like
$400, without anyone questioning the price.

If Heath wants to come back as a kit company, it needs to design products
that have no commercial equivalents.

Heath had an fm tuner with direct frequency entry push button. I never saw
another for home use, but there may have been another or commercial use.

Around about 1974, bought my first led clock, and first calculator. The
clock, cubo, from js&a was unique. Had separate buttons for hours, seconds,
etc. You turned it upside down for snooze.

Greg

 

[micky]

I have 3 Intelli-Time LED alarm clocks around the house, just like the one
here:

I don't think the LEDs are causing the problem.

http://www.acurite.com/clock/alarm-clock/intelli-time-digital-alarm-clock-13027a2.html

I initially bought these due to them keeping time when the power goes off
and auto resetting for DST. There is a problem, however. Each of the
clocks becomes inaccurate over time. If I set them all manually to the same
time, within a few months, each one will be off by 3-5 minutes.

So I ask, what is the problem and is there any way to repair it?

If it's based on a quartz crystal, you could shave a little quartz off
the big piece, or sand it off, or attach some more, depending on if
the clock is slow or fast.

Thanks in advance,
Bill

Just kidding.

 

[micky]

http://www.ebay.com/itm/Westclox-70...915?pt=LH_DefaultDomain_0&hash=item3cc5fe675b

or, if you want to see the display at night

http://www.ebay.com/itm/Atomic-Projection-Alarm-Clock-/310396561330?pt=US_Clocks&hash=item484513a7b2

I've used one of the projection alarm clocks for 4 years now, with the
projector light on 24/7.

When my mother was about 80, I bought something simiilar for her, so
she wouldn't have to roll over to see her clock. But I don't think she
much liked the time on the ceiling. Do you use that? I think the
street lights might have made it hard to see. She didn't mind the
street lights.

I got another one at a yard sale, but I've been sleeping on my belly
or side, so I still have a hard time seeing the ceiling. Worse yet,
the radio is distorted, which is probably why it was only a dollar.
(Well it was on my last trip. I meant to try it here where I know
which stations come in right.)

These clocks were not atomic.

I have a second-hand atomic clock too. I use it to set the time on
my DVDR, which supposedly can set it's own time, but doesn't.

The DVDR doesn't work off of NIST but off of some tv station that
carries the time . Last fall the DVDR got off daylight savings time
by itself, but was still wrong on the minutes! How can that be? On
manual, the clock runs fast 20 seconds a week or so, and a friend
bought the next model, Magnavox instead of Philips, and it does the
same thing. On automatic, it's still wrong by 30 or 60 seconds!

(Ohter than this and a couple other problems, it's a good machine, and
the only one under 600 dolllars designed to work off the air, without
cable or satellite.

 

[N_Cook]

http://www.acurite.com/clock/alarm-clock/intelli-time-digital-alarm-clock-13
027a2.html
http://www.ebay.com/itm/Westclox-70026A-LCD-Atomic-Digital-Alarm-Clock-/2610
19821915?pt=LH_DefaultDomain_0&hash=item3cc5fe675b

or, if you want to see the display at night

http://www.ebay.com/itm/Atomic-Projection-Alarm-Clock-/310396561330?pt=US_Cl
ocks&hash=item484513a7b2

I've used one of the projection alarm clocks for 4 years now, with the
projector light on 24/7.
No problems. Its has battery back-up, but no projection if the power fails.
All the alarm and wall clocks in the house are now atomic. So is my
wristwatch.
IMHO, If a clock doesn't show the correct time, its not a clock...its a
timer.

Confucius , he say, but even a stopped clock tells the right time twice a
day

 

[N_Cook]

--
Jim Yanik
jyanik
at
localnet
dot com

OT:
Have you seen the recent thread on rec.antiques.radio+phono ?

 

[William Sommerwerck]

Heath had an FM tuner with direct frequency entry.

I never saw another for home use, but there may
have been another for commercial use.

Not quite correct.

AFAIK, Heath made the world's first digitally tuned stereo FM tuner. The kit
was appallingly expensive -- around $550 35+ years ago. It used little cards
you notched for a particular station. I saw it at a hi-fi show, with the
Heath rep explaining how you could use it to monitor the station's broadcast
frequency. (In my best Menckenesque manner, I set him straight.)

Tuners with direct frequency entry were and are uncommon, because it
requires a keypad, plus a decoder to output the digital value needed to set
the local oscillator. As the tuner would have a station memory anyway, which
most people would use to store their favorite stations, direct entry has
little advantage (except during initial setup).

GE made at least two clock radios with direct entry. (Yes, I have one.)
Because there's no overlap between AM and FM frequencies (in kHz and MHz),
you didn't need to specify the band.

Component tuners with direct entry are virtually unheard-of. Toshiba had
one, I believe, and my Parasound T3 permits direct entry from the remote
control.

Does anyone know of any others?