From my "I can't believe they'd make it this way" list.

Last year I purchased a new Westinghouse Model WST-3501 microwave oven
for our office lunchroom.

It heats and cooks things fine, but has one lousy feature which I can't
avoid noticing and which irks me very time I see it.

The TOD, which is displayed whenever the unit is on standby, loses about
two minutes a day, and has to be reset every few days to keep from
falling ridiculously behind.

I'm shocked, shocked, that the clock isn't synced to the 120 volt 60 Hz
power the unit runs on, like every other line powered appliance with a
digital TOD display I own.

The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use line
sync for the clock, and probably didn't want to spring for a crystal
oscillator either, so used an RC one instead.

I tried emailing Westinghouse about this and they fobbed me off to a
subsidiary who couldn't even bother to respond to an email.

Thanks for reading. Anyone got any other ideas about why the stupid
clock in this microwave loses time?

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.

On Apr 22, 10:35*am, jeff_wisnia
wrote:
*From my "I can't believe they'd make it this way" list.

Last year I purchased a new Westinghouse Model WST-3501 microwave oven
for our office lunchroom.

It heats and cooks things fine, but has one lousy feature which I can't
avoid noticing and which irks me very time I see it.

The TOD, which is displayed whenever the unit is on standby, loses about
two minutes a day, and has to be reset every few days to keep from
falling ridiculously behind.

I'm shocked, shocked, that the clock isn't synced to the 120 volt 60 Hz
power the unit runs on, like every other line powered appliance with a
digital TOD display I own.

The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use line
sync for the clock, and probably didn't want to spring for a crystal
oscillator either, so used an RC one instead.

I tried emailing Westinghouse about this and they fobbed me off to a
subsidiary who couldn't even bother to respond to an email.

Thanks for reading. Anyone got any other ideas about why the stupid
clock in this microwave loses time?

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.

Yes but some years back our group designed a micro controller project
that used AC line zero cross for phase triggering. Making that
controller into a clock and using 50 or 60 Hz as timing reference
would be as easy for them as it was for us. So THAT isn't a valid
excuse.

G²

Some years back our group designed a micro controller
project that used AC line zero cross for phase triggering.

Did it work by looking for a polarity change, or near-zero voltage? If the
latter, line noise might cause it to miss some zero crossings, and the clock
would run slow.

jeff_wisnia wrote:

I'm shocked, shocked, that the clock isn't synced to the 120 volt 60 Hz
power the unit runs on, like every other line powered appliance with a
digital TOD display I own.

The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use line
sync for the clock, and probably didn't want to spring for a crystal
oscillator either, so used an RC one instead.

I don't think this is a 50/60Hz issue. From the error rate you
describe, it should run faster not slower, and by a larger margin too.

Regardless, locking your clock to mains is not always a great idea.
Some areas are just plain wrong. I have a mains locked clock here that
loses a minute every week or so.
I have cheap non temperature compensated crystal locked clocks that are
by far superior to that.

The answer is worse than that.

The clocks are built to a price, the cheapest possible price.

Consider this: A microwave oven doesn't need a clock at all, just a
timekeeper for timed cooking. Accuracy is not a priority here at all.
The fact they have clocks at all means the manufacturers wanted to get
one leg up on the competitors without expending any money.

We're not talking cameras in cellphones here, there is NO reason for
them to make their clocks accurate, because non of the competition are
going to bother either.
--
To err is human. To moo bovine

On 22/04/2011 18:35, jeff_wisnia wrote:

From my "I can't believe they'd make it this way" list.

Last year I purchased a new Westinghouse Model WST-3501 microwave oven
for our office lunchroom.

It heats and cooks things fine, but has one lousy feature which I can't
avoid noticing and which irks me very time I see it.

The TOD, which is displayed whenever the unit is on standby, loses about
two minutes a day, and has to be reset every few days to keep from
falling ridiculously behind.

I'm shocked, shocked, that the clock isn't synced to the 120 volt 60 Hz
power the unit runs on, like every other line powered appliance with a
digital TOD display I own.

The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use line
sync for the clock, and probably didn't want to spring for a crystal
oscillator either, so used an RC one instead.

I tried emailing Westinghouse about this and they fobbed me off to a
subsidiary who couldn't even bother to respond to an email.

Thanks for reading. Anyone got any other ideas about why the stupid
clock in this microwave loses time?

Probably the clock is line sync'd, and then when cooking, is magnetron
supply sync'd - as critically voltage is lost at the connection point
where the clock takes its time period sample.

Try not cooking for a day and see if that fixes the time loss, then try
using a shorter or heavier cable for the line connection?

--
Adrian C

On 4/22/2011 10:27 PM John Tserkezis spake thus:

Consider this: A microwave oven doesn't need a clock at all, just a
timekeeper for timed cooking. Accuracy is not a priority here at all.
The fact they have clocks at all means the manufacturers wanted to get
one leg up on the competitors without expending any money.

We're not talking cameras in cellphones here, there is NO reason for
them to make their clocks accurate, because non of the competition are
going to bother either.

True now, no doubt, but wasn't always so. My Magic Chef, which I got
used, lessee, 23 years ago or so and still works perfectly, has a very
accurate clock. Crystal-controlled, I'm going to guess.


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)

"David Nebenzahl" wrote in message
s.com...

My Magic Chef, which I got used, lessee, 23 years ago
or so and still works perfectly, has a very accurate clock.
Crystal-controlled, I'm going to guess.

In the US, line frequency used to be (and probably still is) "tweaked" so
that clocks with synchronous motors would have zero net error over a long
period of time. This should give better accuracy than a crystal.

On Apr 22, 12:35*pm, jeff_wisnia
wrote:
*From my "I can't believe they'd make it this way" list.

Last year I purchased a new Westinghouse Model WST-3501 microwave oven
for our office lunchroom.

It heats and cooks things fine, but has one lousy feature which I can't
avoid noticing and which irks me very time I see it.

The TOD, which is displayed whenever the unit is on standby, loses about
two minutes a day, and has to be reset every few days to keep from
falling ridiculously behind.

I'm shocked, shocked, that the clock isn't synced to the 120 volt 60 Hz
power the unit runs on, like every other line powered appliance with a
digital TOD display I own.

The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use line
sync for the clock, and probably didn't want to spring for a crystal
oscillator either, so used an RC one instead.

I tried emailing Westinghouse about this and they fobbed me off to a
subsidiary who couldn't even bother to respond to an email.

Thanks for reading. Anyone got any other ideas about why the stupid
clock in this microwave loses time?

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.

Donate it...and buy a new one. I've never had an appliance with a
digital clock that kept poor time. Coffee maker, oven/range, MW, or
VCR.

On 4/23/2011 7:05 AM, William Sommerwerck wrote:
"David wrote in message
s.com...

My Magic Chef, which I got used, lessee, 23 years ago
or so and still works perfectly, has a very accurate clock.
Crystal-controlled, I'm going to guess.

In the US, line frequency used to be (and probably still is) "tweaked" so
that clocks with synchronous motors would have zero net error over a long
period of time. This should give better accuracy than a crystal.


Correct. In fact back in the early 70s when they had the big
power outage in the NorthEast US my sister was working at a
radio station that checked their electric clock against WWV
every day. When the blackout occurred their clock lost a bunch
of time (I don't remember exactly how much) due to the load
slowing down all of the generators. They reset it and then for
the next week or more they had to set it back every day as the
mains frequency was cranked up a bit until the long term
frequency was returned to 60 Hz. In fact it was for a long
time known that long term stability of the 60 Hz power was
some of the best available. Short term was never as good, it
tended to cycle up and down a bit according to various things
happening.

Bill

"John Tserkezis is a Tserk "


Regardless, locking your clock to mains is not always a great idea.
Some areas are just plain wrong. I have a mains locked clock here that
loses a minute every week or so.


** This ****ing, retarded ****wit has just gotta be totally INSANE !!

The fool has NO IDEA what an energy " supply grid " even is.

Hint - all the alternators are LOCKED IN PHASE all of the time.

No magic - no alternative is even possible for them.





..... Phil

On Apr 22, 10:27*pm, John Tserkezis
wrote:
jeff_wisnia wrote:
I'm shocked, shocked, that the clock isn't synced to the 120 volt 60 Hz
power the unit runs on, like every other line powered appliance with a
digital TOD display I own.
The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use line
sync for the clock, and probably didn't want to spring for a crystal
oscillator either, so used an RC one instead.

*I don't think this is a 50/60Hz issue. *From the error rate you
describe, it should run faster not slower, and by a larger margin too.

*Regardless, locking your clock to mains is not always a great idea.
Some areas are just plain wrong. *I have a mains locked clock here that
loses a minute every week or so.
*I have cheap non temperature compensated crystal locked clocks that are
by far superior to that.

*The answer is worse than that.

*The clocks are built to a price, the cheapest possible price.

*Consider this: A microwave oven doesn't need a clock at all, just a
timekeeper for timed cooking. *Accuracy is not a priority here at all.
*The fact they have clocks at all means the manufacturers wanted to get
one leg up on the competitors without expending any money.

*We're not talking cameras in cellphones here, there is NO reason for
them to make their clocks accurate, because non of the competition are
going to bother either.
--
To err is human. To moo bovine

So you live in a place _not_ on the grid?

G²

On Fri, 22 Apr 2011 13:35:47 -0400, jeff_wisnia
wrote:


From my "I can't believe they'd make it this way" list.

Last year I purchased a new Westinghouse Model WST-3501 microwave oven
for our office lunchroom.

It heats and cooks things fine, but has one lousy feature which I can't
avoid noticing and which irks me very time I see it.

The TOD, which is displayed whenever the unit is on standby, loses about
two minutes a day, and has to be reset every few days to keep from
falling ridiculously behind.

[snip]

Jeff

I have a small coffee maker that has never kept good time. My guess
is that *any* noise on the AC line affects the pulse counting. I have
a weather station whose clock is synced to NIST, so no longer bother
to set the clock on the coffee maker.

John

On Apr 23, 10:02*am, wrote:



I have a small coffee maker that has never kept good time. *My guess
is that *any* noise on the AC line affects the pulse counting. *I have
a weather station whose clock is synced to NIST, so no longer bother
to set the clock on the coffee maker.

John

So...a surge suppressor might fix it?

On Apr 22, 5:29*pm, "William Sommerwerck"
wrote:
Some years back our group designed a micro controller
project that used AC line zero cross for phase triggering.

Did it work by looking for a polarity change, or near-zero voltage? If the
latter, line noise might cause it to miss some zero crossings, and the clock
would run slow.

It looked for zero crossings directly into the interrrupt input (via a
comparator to clean it up). I had many more problems with extra rather
than missing pulses. That was solved easily by using one of the
processor timers to disable interrupts until almost time for the next
external. I really need to implement the WWVB receiver to REALLY keep
it accurate.

G²

On Sat, 23 Apr 2011 12:08:43 -0700 (PDT), wrote:

I really need to implement the WWVB receiver to REALLY keep
it accurate.

Maybe. In about 2005, I got a consulting gig to clean up a WWVB
receiver design inside a microwave oven. Operation was deemed erratic
by the engineers. I had 1 week to pull off a miracle, and predictably
failed. The product was released with a ceramic resonator.

I'll spare you the details, but methinks it won't work. The basic
problems a
1. WWVB does not have world wide coverage. You'll need a receiver
that scans from 40 to 100Khz looking for time sync signals. Of
course, every country has their own protocol. Such chips are
available today, but were not when I was dealing with the problem:
http://www.c-max-time.com/products/showProduct.php?id=1
2. To get decent field sensitivity, I needed a big fat loopstick like
this:
http://www.sparkfun.com/products/10060
http://www.c-max-time.com/tech/antenna.php
The problem is that the Q is sufficiently high that it won't cover the
entire 40 to 100KHz range. Lower Q would work, but at reduced
sensitivity. Just finding a place for the loopstick was a challenge
as it had to be outside the metal cabinet. Manufacturing went
ballistic when they saw the loopstick and announced that the hand
labor involved would dramatically raise the price. They were right.
3. Interference from switching supplies and digital rubbish can be
fatal. A 20Khz switcher will have enough harmonics to kill the LF
receiver. I convinced them to turn off the LED display as a token
"energy conservation" measure. However, my switching cell phone
charger would kill the receiver up to a distance of about 10 ft.
4. The controller group wanted a WWVB disciplined oscillator at any
of the standard CPU clock frequencies (i.e. 3.57Mhz). However, none
of the off the shelf chips offered this feature. As a compromise,
they asked for 1 pps, which was also not offered. When I offered to
feed them encoded BCD character data, they threatened to have me fired
for incompetence.
5. Whatever else I forgot...

At this time, I would suspect it can be done with a GPS receiver. High
sensitivity GPS receivers will product accurate time sync even
indoors.
http://en.wikipedia.org/wiki/High_Sensitivity_GPS
It may take nearly forever to obtain sync, but for a microwave oven,
that only needs to be done once or twice per day. If location is an
issue, I can extract the time from some various broadcast and cellular
services:
http://en.wikipedia.org/wiki/Radio_clock

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

On Fri, 22 Apr 2011 13:35:47 -0400, jeff_wisnia
wrote:

Last year I purchased a new Westinghouse Model WST-3501 microwave oven
for our office lunchroom.

The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use line
sync for the clock, and probably didn't want to spring for a crystal
oscillator either, so used an RC one instead.

Did you look to see what they actually used? My guess(tm) would be a
PZT ceramic resonator.
http://www.tdk.co.jp/tefe02/ef32_fcr.pdf
These have an initial tolerance of about 0.3% to 0.5%, which is a
rather large:
24 hrs/day * 3600 sec/hr * 0.0005 = 43.2 seconds/day
If you're losing 120 sec/day, then something is wrong with the ceramic
resonator, the associated capacitors, or the CPU. Since you're losing
time (running slow), the clock oscillator frequency is too low, so
it's probably not the capacitor. Find the frequency, identify the
CPU, and install a replacement resonator.
http://www.tdk.com/crdata.php


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

(and Phil) wrote:

So you live in a place _not_ on the grid?

Sigh.

I do live on the grid. I, along with everyone else was promised that
while short term timing errors on the grid are expected, longer term
errors are tweaked and by far less.
I could have lived with this if they actually meant it.

However, in real life, it's STILL not good enough for clocks. Like I
said, I have many non-temperature crystal locked clocks that are by FAR
better.

I have cheap Chinese digital watches (NOT on my wrist) at the whim of
the seasonal temperature environment that have minor seasonal shifts,
but over the year are better than mains-locked clocks.

I can't even get a straight answer googling. Lots of nice graphs that
really don't answer the question too. The BEST was along the lines of
"is very precise" and "it shouldn't vary too far".

In engineering terms, that's just plain bull****.
--
Include this in your CONFIG.SYS File: BUGS=OFF

Bob Villa wrote:

Donate it...and buy a new one. I've never had an appliance with a
digital clock that kept poor time. Coffee maker, oven/range, MW, or
VCR.

You mean you had a VCR that *DIDN'T* flash 12:00 all day?

That could only mean one of two things:
You're either a Rocket Scientist, or you had a six-year-old around.
--
If it's not worth doing well, it's not worth doing.

"John Tserkezis" wrote in message
u...

You mean you had a VCR that *DIDN'T* flash 12:00 all day?

Most Public TV stations broadcast time code. The "later" VHS VCRs searched
for a PBS station and used the time code to set the clock.

William Sommerwerck wrote:

"John Tserkezis" wrote in message
u...

You mean you had a VCR that *DIDN'T* flash 12:00 all day?

Most Public TV stations broadcast time code. The "later" VHS VCRs searched
for a PBS station and used the time code to set the clock.

Sorry, my email addy doesn't show it, but I'm in Australia. I've
verified that timing codes are NOT sent by ANY networks here.
More so, of the few that knew what I was talking about, said they had
heard of it, but no, they did not, and never will support it.

That was about a decade ago while digital terrestrial TV was still a
bit experimental here, but even then, I don't know of any digital PVRs
today that maintain time that way.
There's the odd one out that does NTP if they're 'net connected, but
everything else relies on standard crystal clocked circuits.
Probably a bad example though. At that that level of complexity,
no-one in their right mind would go to the trouble of mains-locking a
clock, when implementing a single-chip Real Time Clock is so much
easier. Especially so when RTC functionality is built into other multi
purpose chips.


I suppose this comes down to the question of is mains locking "good
enough"?
Since I can't get a clear answer from anyone, I'm staying with crystals
or NTP where applicable.
--
OUCH! Got my floppy caught in my PKZipper!

Jeff Liebermann wrote:

... Find the frequency, identify the
CPU, and install a replacement resonator.
http://www.tdk.com/crdata.php

At this price-point, there is no "CPU" to look for. They're all Chip
On Board designs (the black blob on the PCB itself).

The resonator would be a separate component, and I wouldn't think that
an RC oscillator would be good enough to keep mere minutes within a day
anyway.

Besides simply replacing the resonator probably wouldn't show any
significant improvement. You'd need to go all out and use an
upper-market crystal, associated oscillator (with fine tuning) and drive
the clock that way. Would likely need some divider in there too if you
can't match the frequency otherwise.

And now you're starting to lean into the "not worth it" territory.
--
No matter where you go, there you are.

On Sun, 24 Apr 2011 11:10:13 +1000, John Tserkezis
wrote:

Jeff Liebermann wrote:

... Find the frequency, identify the
CPU, and install a replacement resonator.
http://www.tdk.com/crdata.php

At this price-point, there is no "CPU" to look for. They're all Chip
On Board designs (the black blob on the PCB itself).

Are you sure? I haven't repaired enough modern microwave ovens to
even have an opinion, but I have yet to see such a PCB. The problem
is that there are usually a mess of wires that need to connect to
various components in the microwave oven. Handling a black glob PCB
usually breaks the wire bonds. Black glob boards are usually more
suitable for enclosed devices and robotic assembly such as
calculators.

I also gave myself a Google Images tour of "microwave oven PCB" and
variations. There were only about 50 assorted images of such PCB's
and none of them showed a black glob.

The resonator would be a separate component, and I wouldn't think that
an RC oscillator would be good enough to keep mere minutes within a day
anyway.

They're available in surface mount packages and are difficult to
distinguish from a large capacitor.

Besides simply replacing the resonator probably wouldn't show any
significant improvement.

I beg to differ. It's probably off frequency for some reason, and
would bring it closer to acceptable. 120 seconds per day is lousy. 40
seconds per day might be a little less lousy.

You'd need to go all out and use an
upper-market crystal, associated oscillator (with fine tuning) and drive
the clock that way. Would likely need some divider in there too if you
can't match the frequency otherwise.

Yep. However, if the CPU can be identified, the data sheet usually
has instructions for using the internal clock oscillator with either
crystal, ceramic resonator, or external input. At worst, it would
involve also changing 2 capacitors.

And now you're starting to lean into the "not worth it" territory.

I've been there many times. I'm one of those compulsive repairmen
that insists on fixing things, even if they're not profitable.
Personally, I like the ceramic resonator type real time clocks because
when the power dies, and if they have a backup battery, they keep
running. Unfortunately, most microwave ovens don't even have a big
capacitor to keep the time during minor power interruptions, so it's
kinda a wasted preference.

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

"John Tserkezis is a MASSIVE JERK"

So you live in a place _not_ on the grid?

Sigh.

I do live on the grid.

** He lives in Sydney - same as me.


I, along with everyone else was promised that
while short term timing errors on the grid are expected, longer term
errors are tweaked and by far less.
I could have lived with this if they actually meant it.

** The do actually - ****head.


However, in real life, it's STILL not good enough for clocks. Like I
said, I have many non-temperature crystal locked clocks that are by FAR
better.

** That is complete ********.


I have cheap Chinese digital watches (NOT on my wrist) at the whim of
the seasonal temperature environment that have minor seasonal shifts,
but over the year are better than mains-locked clocks.

** The problem is not with the frequency of the AC supply.


I can't even get a straight answer googling. Lots of nice graphs that
really don't answer the question too. The BEST was along the lines of
"is very precise" and "it shouldn't vary too far".

In engineering terms, that's just plain bull****.


** The supply grid has absolutely precise time keeping over the long term.

The PROBLEM is that any given premises may suffer losses of power for short
periods from time to time - over a year these all add up of course. And
they all add in the same direction !!!!

Most mains derived clocks react to a power outage by going into a mode where
the display blinks and the time resets to midnight or some such. OTHERS
( with battery back up) however revert to an internal oscillator that is
only based on a cheap R and C and give no warning that there has been an
outage.

The most common outages in homes are due to ELCBs and breakers tripping.


..... Phil

On Sun, 24 Apr 2011 10:58:06 +1000, John Tserkezis
wrote:

William Sommerwerck wrote:

"John Tserkezis" wrote in message
u...

You mean you had a VCR that *DIDN'T* flash 12:00 all day?

Most Public TV stations broadcast time code. The "later" VHS VCRs searched
for a PBS station and used the time code to set the clock.

Sorry, my email addy doesn't show it, but I'm in Australia. I've
verified that timing codes are NOT sent by ANY networks here.

Are you talking about analog TV or digital TV? With analog, it was at
the discretion of the station. With digital, it's inscribed into the
ATSC (US) and DVB-T (everyone else) standards. Unfortunately, I don't
know enough about either of these to explain how to get to these time
codes.

More so, of the few that knew what I was talking about, said they had
heard of it, but no, they did not, and never will support it.

In the US, the local PBS station (KTEH) went the other way. They
claim to be sending time code signals, but none of my 3 assorted VCR
boxes would find it.

That was about a decade ago while digital terrestrial TV was still a
bit experimental here, but even then, I don't know of any digital PVRs
today that maintain time that way.

Nope. I have a Philips HDRW720. It can use a PBS station for real
time setting. See the owners manual at:
http://download.p4c.philips.com/files/h/hdrw720_17b/hdrw720_17b_dfu_aen.pdf
on page 22 under "automatic time setting". The problem is that there
has been no firmware update to deal with the 2007 change in daylight
savings time.

My Tivo 2 can also use a PBS station for date and time, when connected
to an antenna.

Most digital DVR's are now integrated with either a cable TV modem or
a satellite receiver. Time sync comes from the network. My DirecTV
R16-300 DVR is about 3 seconds early, for no obvious reason, which
makes time shifted recordings start 3 seconds early, and chop off 3
seconds from the end. Grrr....

There's the odd one out that does NTP if they're 'net connected, but
everything else relies on standard crystal clocked circuits.

Samsung combined Blue-Ray players and DVR work that way. Buried in
the setup is the option to specify an NTP server. I like to use:
us.pool.ntp.org

Probably a bad example though. At that that level of complexity,
no-one in their right mind would go to the trouble of mains-locking a
clock, when implementing a single-chip Real Time Clock is so much
easier. Especially so when RTC functionality is built into other multi
purpose chips.

Yep. However, if the functionality is there as in a network connected
device, and the computer horsepower is available, then network time is
just a matter of adding some code.

I suppose this comes down to the question of is mains locking "good
enough"?

It's marginal. Loss of power means loss of clock, with no automatic
method of restoring the real time. No thanks.

Since I can't get a clear answer from anyone, I'm staying with crystals
or NTP where applicable.

Perhaps a wind up clock would suffice?

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

On Apr 23, 5:36*am, "William Sommerwerck"
wrote:
The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use
line sync for the clock, and probably didn't want to spring for
a crystal oscillator either, so used an RC one instead.

A chip would likely be designed to work at either frequency, with a jumper
making the selection.

IF it is set to 50HZ and you are on a 60HZ supply - then it would run
faster, not slower.

Open it up and see if there is some sort of trimmer capacitor there
near the clock chip, adjust it and see what happens. Might have to
fiddle with it
over some time to get it right

"KR" wrote in message
...
On Apr 23, 5:36 am, "William Sommerwerck"
wrote:

The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use
line sync for the clock, and probably didn't want to spring for
a crystal oscillator either, so used an RC one instead.

A chip would likely be designed to work at either frequency,
with a jumper making the selection.

IF it is set to 50HZ and you are on a 60HZ supply -- then it
would run faster, not slower.

That has nothing whatever to do with the point I was making.


Open it up and see if there is some sort of trimmer capacitor
near the clock chip, adjust it and see what happens. Might
have to fiddle with it over some time to get it right.

I find it impossible to believe that /any/ microwave oven would use a
crystal or resonator -- which costs money -- when the power frequency is
/right there/, and free.

William Sommerwerck wrote:

"KR" wrote in message
...
On Apr 23, 5:36 am, "William Sommerwerck"
wrote:

The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use
line sync for the clock, and probably didn't want to spring for
a crystal oscillator either, so used an RC one instead.

A chip would likely be designed to work at either frequency,
with a jumper making the selection.

IF it is set to 50HZ and you are on a 60HZ supply -- then it
would run faster, not slower.

That has nothing whatever to do with the point I was making.

Open it up and see if there is some sort of trimmer capacitor
near the clock chip, adjust it and see what happens. Might
have to fiddle with it over some time to get it right.

I find it impossible to believe that /any/ microwave oven would use a
crystal or resonator -- which costs money -- when the power frequency is
/right there/, and free.


They would use the same crystal as the microprocessor, and run the
clock in software.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

Jeff Liebermann wrote:

Sorry, my email addy doesn't show it, but I'm in Australia. I've
verified that timing codes are NOT sent by ANY networks here.

Are you talking about analog TV or digital TV? With analog, it was at
the discretion of the station. With digital, it's inscribed into the
ATSC (US) and DVB-T (everyone else) standards. Unfortunately, I don't
know enough about either of these to explain how to get to these time
codes.

I was talking about analogue. Digital here has only appeared in the
last decade or so, and even then, early on, there were no boxes you
could actually buy to do that. (funny though, the politicians could get
wide screen TVs and set top boxes donated quite easily to them - for
"testing purposes" you understand).

It's only the last few years the prices have come down to something
that's actually reasonable.

On the analogue side, we had *electronics* here that was compatible
with a variety of systems around the world for a LONG time, non of which
were compatible with our TV stations.

In the US, the local PBS station (KTEH) went the other way. They
claim to be sending time code signals, but none of my 3 assorted VCR
boxes would find it.

At least you had TV stations that WERE transmitting codes, we didn't.
Not till digital anyway.

on page 22 under "automatic time setting". The problem is that there
has been no firmware update to deal with the 2007 change in daylight
savings time.

Arrg. Don't start me on daylight savings. I'm actively unimpressed
unless the device supports USER DEFINABLE dst rules.

My Tivo 2 can also use a PBS station for date and time, when connected
to an antenna.

TiVo is another thing that failed miserably in Australia. The group in
charge of keeping things running in Australia and New Zealand is down to
7 people (from 100+?) and will only keep the current licence holders
going till that runs out.
Shame really. If it actually worked like it does in the US, it would
be quite viable. Except they knobbled a lot of the functionality, and
charged more for the privileged.

I suppose this comes down to the question of is mains locking "good
enough"?

It's marginal. Loss of power means loss of clock, with no automatic
method of restoring the real time. No thanks.

That's pretty much my attitude. Mains locking is cheaper to implement
than crystal locking, and if mains locking was better than crystal then
no-one would implement cyrstal locking in the first place.
But it IS better, AND you get very viable long term battery backed
timekeeping with crystals too. That leaves no reason for mains locked
clocks to be implemented at all, outside of "novelty" clocks. Really,
is saving two cents really worth it when you're ****ing off your
customers that much?

Since I can't get a clear answer from anyone, I'm staying with crystals
or NTP where applicable.

Perhaps a wind up clock would suffice?

I don't do windups. Outside of antiques that is.
But an antique isn't a timepiece, it's an example of a combination of
the limited technology of the day, doing a job that a two dollar Chinese
wrist-strapped device can today.
--
None of you exist, my Sysop types all this in.

I find it impossible to believe that /any/ microwave oven
would use a crystal or resonator -- which costs money --
when the power frequency is /right there/, and free.

They would use the same crystal as the microprocessor,
and run the clock in software.

I was, of course, referring to a separate crystal (he said, retro-conning
the issue).

William Sommerwerck wrote:

I find it impossible to believe that /any/ microwave oven
would use a crystal or resonator -- which costs money --
when the power frequency is /right there/, and free.

They would use the same crystal as the microprocessor,
and run the clock in software.

I was, of course, referring to a separate crystal (he said, retro-conning
the issue).


William, I've never seen a microwave where the clock wasn't just
software in the MPU and I've scrapped a lot of them over the years.
Just one 20 cent crystal, and a MPU that cost less than a dollar in
production quantities.


--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.

On Apr 25, 9:05*pm, "William Sommerwerck"
wrote:
I find it impossible to believe that /any/ microwave oven
would use a crystal or resonator -- which costs money --
when the power frequency is /right there/, and free.
They would use the same crystal as the microprocessor,
and run the clock in software.

I was, of course, referring to a separate crystal (he said, retro-conning
the issue).


It is possible to have a second crystal, as I have seen a custom IC
that included an RTC inside have its own separate 3.579mhz
crystal in addition to the crystal for the CPU function. Both
connected to the same IC on separate pins.
In this case though, this second crystal would be just for the RTC
function,
as the low speed would save power, and also the rest of the chip would
likely be shut down also to save power hence no software clock.
This was an early 1990s design



As microwaves don't have a RTC in them (that I have seen) and simply
reset to 12:00 or whatever after a power failure,
there is no need for the more sophisticated system described above.



I agree with Michael A Terrell,

There wouldn't be a separate crystal for the clock in a modern
microwave,
The "clock" and processor would be incorporated into a single chip,
and the timekeeping would
be surely a software function. The chip would very likely have a
single crystal
or resonator.

In my original comment, I suggested looking for a trimmer cap
across the crystal and trimming it to fine adjust the clock if the
inaccuracy is a real issue for the OP .

You also can check the value of the crystal, there is also a very very
remote possibility that there was the wrong value, but very close
installed at the factory - something like a 3.562 MHZ instead of a
3.579545 MHZ
for example, but without sitting and working out the inaccuracy this
would cause, this might not be right and might make too big a
difference to be the problem.


It will not hurt the rest of the system to run a tiny fraction faster/
slower.

On Wed, 27 Apr 2011 06:50:05 -0700 (PDT), KR
wrote:

On Apr 25, 9:05*pm, "William Sommerwerck"
wrote:
I find it impossible to believe that /any/ microwave oven
would use a crystal or resonator -- which costs money --
when the power frequency is /right there/, and free.
They would use the same crystal as the microprocessor,
and run the clock in software.

I was, of course, referring to a separate crystal (he said, retro-conning
the issue).


It is possible to have a second crystal, as I have seen a custom IC
that included an RTC inside have its own separate 3.579mhz
crystal in addition to the crystal for the CPU function. Both
connected to the same IC on separate pins.
In this case though, this second crystal would be just for the RTC
function,
as the low speed would save power, and also the rest of the chip would
likely be shut down also to save power hence no software clock.
This was an early 1990s design



As microwaves don't have a RTC in them (that I have seen) and simply
reset to 12:00 or whatever after a power failure,
there is no need for the more sophisticated system described above.

That IS a RTC. It just has no battery backup to ride through power
outages.

I agree with Michael A Terrell,

There wouldn't be a separate crystal for the clock in a modern
microwave,
The "clock" and processor would be incorporated into a single chip,
and the timekeeping would
be surely a software function. The chip would very likely have a
single crystal
or resonator.

In my original comment, I suggested looking for a trimmer cap
across the crystal and trimming it to fine adjust the clock if the
inaccuracy is a real issue for the OP .

You also can check the value of the crystal, there is also a very very
remote possibility that there was the wrong value, but very close
installed at the factory - something like a 3.562 MHZ instead of a
3.579545 MHZ

It would save a lot more power at 32,786 Hz, which is also standard for
the application.

for example, but without sitting and working out the inaccuracy this
would cause, this might not be right and might make too big a
difference to be the problem.


It will not hurt the rest of the system to run a tiny fraction faster/
slower.

On Apr 29, 3:28*am, josephkk wrote:
On Wed, 27 Apr 2011 06:50:05 -0700 (PDT), KR
wrote:



On Apr 25, 9:05*pm, "William Sommerwerck"
wrote:
I find it impossible to believe that /any/ microwave oven
would use a crystal or resonator -- which costs money --
when the power frequency is /right there/, and free.
They would use the same crystal as the microprocessor,
and run the clock in software.

I was, of course, referring to a separate crystal (he said, retro-conning
the issue).

It is possible to have a second crystal, as I have seen a custom IC
that included an RTC inside have its own separate 3.579mhz
crystal in addition to the crystal for the CPU function. Both
connected to the same IC on separate pins.
In this case though, this second crystal would be just for the RTC
function,
as the low speed would save power, and also the rest of the chip would
likely be shut down also to save power hence no software clock.
This was an early 1990s design

As microwaves don't have a RTC in them (that I have seen) and simply
reset to 12:00 or whatever after a power failure,
there is no need for the more sophisticated system described above.

That IS a RTC. *It just has no battery backup to ride through power
outages.



Sorry - I was referring to a RTC as a dedicated clock IC either in or
out of a custom IC.
battery backed up

I would think that a microwave clock would be done in software though,
and not have
a dedicated clock section in the custom IC, not that it matters
though.

On Fri, 29 Apr 2011 22:15:18 -0700 (PDT), KR
wrote:

On Apr 29, 3:28*am, josephkk wrote:
On Wed, 27 Apr 2011 06:50:05 -0700 (PDT), KR
wrote:



On Apr 25, 9:05*pm, "William Sommerwerck"
wrote:
I find it impossible to believe that /any/ microwave oven
would use a crystal or resonator -- which costs money --
when the power frequency is /right there/, and free.
They would use the same crystal as the microprocessor,
and run the clock in software.

I was, of course, referring to a separate crystal (he said, retro-conning
the issue).

It is possible to have a second crystal, as I have seen a custom IC
that included an RTC inside have its own separate 3.579mhz
crystal in addition to the crystal for the CPU function. Both
connected to the same IC on separate pins.
In this case though, this second crystal would be just for the RTC
function,
as the low speed would save power, and also the rest of the chip would
likely be shut down also to save power hence no software clock.
This was an early 1990s design

As microwaves don't have a RTC in them (that I have seen) and simply
reset to 12:00 or whatever after a power failure,
there is no need for the more sophisticated system described above.

That IS a RTC. *It just has no battery backup to ride through power
outages.



Sorry - I was referring to a RTC as a dedicated clock IC either in or
out of a custom IC.
battery backed up

I would think that a microwave clock would be done in software though,
and not have
a dedicated clock section in the custom IC, not that it matters
though.


I'm cool with this. No worries.
Plus there are plenty of uC that could wake up once per second just enough
to keep good time, but a crystal and battery are more parts and cost.

On Apr 22, 12:35*pm, jeff_wisnia
wrote:
*From my "I can't believe they'd make it this way" list.

Last year I purchased a new Westinghouse Model WST-3501 microwave oven
for our office lunchroom.

It heats and cooks things fine, but has one lousy feature which I can't
avoid noticing and which irks me very time I see it.

The TOD, which is displayed whenever the unit is on standby, loses about
two minutes a day, and has to be reset every few days to keep from
falling ridiculously behind.

I'm shocked, shocked, that the clock isn't synced to the 120 volt 60 Hz
power the unit runs on, like every other line powered appliance with a
digital TOD display I own.

The only reason I can guess for the poor timekeeping is that the
circuitry/board running the clock is used on their 220 volt 50 Hz
versions without modification, so the makers decided not to use line
sync for the clock, and probably didn't want to spring for a crystal
oscillator either, so used an RC one instead.

I tried emailing Westinghouse about this and they fobbed me off to a
subsidiary who couldn't even bother to respond to an email.

Thanks for reading. Anyone got any other ideas about why the stupid
clock in this microwave loses time?

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.

Why not donate the SOB and get a new one for $40 and STFU!