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]

Bill Proms <none@anywhere.us> wrote in message
news:jp850p$fk2$1@dont-email.me...

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]

On 19 May 12 at group /sci/electronics/repair in article
<diverse@tcp.co.uk> (N_Cook) wrote:

Bill Proms <none@anywhere.us> wrote in message
news:jp850p$fk2$1@dont-email.me...
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

--
Wolfgang Allinger 15h00..21h00 MEZ: SKYPE:wolfgang.allinger
Paraguay mailer: CrossPoint XP 3.20 (XP2) in WinXPprof DOSbox
Meine 7 Sinne: reply Adresse gesetzt!
Unsinn, Schwachsinn, Bloedsinn, Wahnsinn, Stumpfsinn, Irrsinn, Loetzinn.

 

[Pat]

On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms" <none@anywhere.us>
wrote:

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
You didn't mention if there had been actual power interruptions during

the period you are measuring. Most inexpensive clocks use the power
line frequency to keep time when they have power, but use a cheap
oscillator when the power is off. I have one that keeps very good
time normally, but during a power outage, it runs very fast (gains 5
minutes per hour). That is good in that the alarm goes off in time
for me to get up and go to work, but I always have to reset the time
after a power outage. Some of your clocks might be close while others
are way off but only during a power outage.

Pat

 

[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


"Pat" <pat@nospam.us> wrote in message
news:fi6fr796klao1hi5fnh9706ufq5sregf9m@4ax.com...

On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms" <none@anywhere.us
wrote:

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
You didn't mention if there had been actual power interruptions during
the period you are measuring. Most inexpensive clocks use the power
line frequency to keep time when they have power, but use a cheap
oscillator when the power is off. I have one that keeps very good
time normally, but during a power outage, it runs very fast (gains 5
minutes per hour). That is good in that the alarm goes off in time
for me to get up and go to work, but I always have to reset the time
after a power outage. Some of your clocks might be close while others
are way off but only during a power outage.

Pat

 

[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-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.

 

[Jeff Liebermann]

On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms" <none@anywhere.us>
wrote:

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?

Several problems and combination of problems.
1. Noise on the power lines triggering added pulses. This will make
the clock run fast.
2. Internal free running oscillator is off frequency.
3. Crappy design.

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.

These daze, there are alarm clocks that use a WWVB 60Khz receiver to
keep accurate time. I have one of these. When the power dies, the
piece of junk still has a crappy RC oscillator. The 9V battery runs
down in about 12 hrs (progress, I guess), and still doesn't have an
internal recharger for the 9V battery. The way it works is really
bizarre. If the power dies in the morning, the clock drifts around
(usually slows down) all day because the receiver can't hear the 60KHz
signal until late at night. After midnight, the clock hears the WWVB
signal, and sets the clock to the correct time. Not great, but
functional. Meanwhile, the 9V battery is half way discharged. The
next time the power dies for an extended period, the battery usually
runs down to near zero. When the power then returns, the clock
doesn't drift around, but displays the dreaded flashing 12:00AM. I
can either set it manually, or wait until after midnight for WWVH to
do it for me. So much for progress.

How Accurate is a Radio Controlled Clock?
<http://tf.nist.gov/general/pdf/2429.pdf>

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[N_Cook]

William Sommerwerck <grizzledgeezer@comcast.net> wrote in message
news:jp8956$77f$1@dont-email.me...

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.

 

[Jeff Liebermann]

On Sat, 19 May 2012 09:46:00 -0400, "Bill Proms" <none@anywhere.us>
wrote:

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.

You probably won't find an LED or vacuum fluorescent WWVB atomic
clock. The problem is RFI/EMI from the high power of the LED display
will produce enough RF hash to prevent the WWVB receiver from
functioning. I accidentally produced this problem when I put my LED
alarm clock too close to my LCD weather station. The weather station
has a WWVB receiver to set the time, but it never seemed to work. When
daylight savings time came and went, but the weather station didn't
change time, I decided to investigate. A portable AM radio near the
LED clock confirmed the RFI/EMI problem. Physically seperating the
devices by about 3 meters was sufficient to allow the WWVB receiver to
operate normally.

When I Google for "LED Atomic Clock", I get plenty of hits, all
showing LCD displays. However, there are many clocks that have LCD
displays, but also have an LED projector that displays the time on the
ceiling. However, this single digit display is NOT multiplexed, and
therefore generates no RFI/EMI hash.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sat, 19 May 2012 07:53:46 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

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.

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 jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Ian Field]

"Bill Proms" <none@anywhere.us> wrote in message
news:jp886o$1c6$1@dont-email.me...

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.

In the UK we have MSF60 (60kHz time signal) and Europe the DCF 70, so far
I've yet to see a compatible clock with LED display.

My solution is to have a mains synchronised LED clock sitting next to a
MSF60 LCD clock - then simply adjust the LED clock whenever it gets a minute
or 2 out of step.

It might be possible to test the spikes causing extra clock cycles theory by
gutting a small PC PSU box that has filtered mains inlet and adding more
capacitors and MOV or sidac spike protection.

The mains "in spec" frequency is actually an average - at peak demand its
allowed to be slow, and catches up at off peak times when they can run the
generators a little faster with little energy expenditure.

Depending what time of day you check the time; a mains sync clock can be
slow, fast or just right.

 

[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.

 

[gregz]

"N_Cook" <diverse@tcp.co.uk> wrote:

Bill Proms <none@anywhere.us> wrote in message
news:jp850p$fk2$1@dont-email.me...
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.

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

Greg

 

[N_Cook]

Jeff Liebermann <jeffl@cruzio.com> wrote in message
news:h9dfr71u6fchkgccmmpjd31m95ifn47s6k@4ax.com...

On Sat, 19 May 2012 07:53:46 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:

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.

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 jeffl@cruzio.com
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

 

[Jeff Liebermann]

On Sat, 19 May 2012 18:24:04 +0000 (UTC), "Geoffrey S. Mendelson"
<gsm@mendelson.com> wrote:

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

I beg to differ. The cost of a GPS disciplined oscillator or clock in
a consumer product is prohibitive. Running continuously, GPS is a
major power drain. GPS doesn't work well indoors. There are huge
number of products that currently use 60KHz time sync that will go
dark if the US pulls the plug on WWVH and WWVB. That's not going to
happen. Quite the contrary, there are plans to add a US east coast
transmitter. See:
<http://en.wikipedia.org/wiki/WWVB>
under "Service Improvement Plans".

Incidentally, I'm building my own 10MHz GPSDO for running my test
eqipment and ham junk. It's NOT a trivial or inexpensive exercise:
<http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm>
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jim Yanik]

Jeff Liebermann <jeffl@cruzio.com> wrote in
news:2hafr7t16440eur5henfoq8rl2sj9ie9sk@4ax.com:

On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms" <none@anywhere.us
wrote:

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-clo
ck-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?

Several problems and combination of problems.
1. Noise on the power lines triggering added pulses. This will make
the clock run fast.
2. Internal free running oscillator is off frequency.
3. Crappy design.

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.

was that a 32KHz crystal,or a 32KHz ceramic resonator?
I suspect it's the latter.that would explain the poor freq.stability.
You can trim up an XTAL oscillator.

--
Jim Yanik
jyanik
at
localnet
dot com

 

[Ian Field]

"gregz" <zekor@comcast.net> wrote in message
news:1124369627359136873.854687zekor-comcast.net@news.eternal-september.org...

"N_Cook" <diverse@tcp.co.uk> wrote:
Bill Proms <none@anywhere.us> wrote in message
news:jp850p$fk2$1@dont-email.me...
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.

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

Even one I bought recently uses mains sync, but it has a battery & crystal
divider backup to cover outages.

The mains frequency varies depending on peak demand/off peak, but long term
its average has less drift than the cheap crystal oscillator they're going
to put in a radio alarm clock.

 

[Ian Field]

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:gkqfr7tifijlt1n4l7frdrb5pumccv7tad@4ax.com...

On Sat, 19 May 2012 18:24:04 +0000 (UTC), "Geoffrey S. Mendelson"
gsm@mendelson.com> wrote:

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

I beg to differ. The cost of a GPS disciplined oscillator or clock in
a consumer product is prohibitive. Running continuously, GPS is a
major power drain. GPS doesn't work well indoors. There are huge
number of products that currently use 60KHz time sync that will go
dark if the US pulls the plug on WWVH and WWVB. That's not going to
happen. Quite the contrary, there are plans to add a US east coast
transmitter. See:
http://en.wikipedia.org/wiki/WWVB
under "Service Improvement Plans".

Incidentally, I'm building my own 10MHz GPSDO for running my test
eqipment and ham junk. It's NOT a trivial or inexpensive exercise:

A while back (I think it was) EPE magazine (or might have been Elektor)
published a GPS frequency standard generator projects.

Its available as a kit, so although not particularly cheap it is fairly
easy.

 

[Ian Field]

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:h9dfr71u6fchkgccmmpjd31m95ifn47s6k@4ax.com...

On Sat, 19 May 2012 07:53:46 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:

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.

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

They finally figured out the battery won't run the LED display for long and
rigged it to blank during outages.