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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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LED alarm clocks all lose accuracy over time
I have 3 Intelli-Time LED alarm clocks around the house, just like the one
he http://www.acurite.com/clock/alarm-c...k-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 |
#2
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LED alarm clocks all lose accuracy over time
Bill Proms wrote in message
... I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...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. |
#3
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LED alarm clocks all lose accuracy over time
On 19 May 12 at group /sci/electronics/repair in article (N_Cook) wrote: Bill Proms wrote in message ... I have 3 Intelli-Time LED alarm clocks around the house, just like the one he [...] 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. |
#4
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms"
wrote: I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...k-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 |
#5
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LED alarm clocks all lose accuracy over time
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" wrote in message ... On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms" wrote: I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...k-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 |
#6
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LED alarm clocks all lose accuracy over time
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-Instrum...5811&sr= 1-22 You might look for atomic clocks using vacuum-fluorescent displays. |
#7
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms"
wrote: I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...k-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 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#8
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LED alarm clocks all lose accuracy over time
William Sommerwerck wrote in message
... 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-Instrum.../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 |
#9
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LED alarm clocks all lose accuracy over time
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. |
#10
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 09:46:00 -0400, "Bill Proms"
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 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#11
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 07:53:46 -0700, "William Sommerwerck"
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 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#12
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LED alarm clocks all lose accuracy over time
"Bill Proms" wrote in message ... 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. |
#13
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LED alarm clocks all lose accuracy over time
"N_Cook" wrote:
Bill Proms wrote in message ... I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...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 |
#14
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LED alarm clocks all lose accuracy over time
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. |
#15
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LED alarm clocks all lose accuracy over time
Bill Proms 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. It's because the US is trying to get rid of those broadcasts. With GPS they are obsolete. Geoff. -- Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379 In 1969 the US could put a man on the moon, now teenagers just howl at it. :-( |
#16
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LED alarm clocks all lose accuracy over time
Bill Proms wrote:
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. -- Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379 In 1969 the US could put a man on the moon, now teenagers just howl at it. :-( |
#17
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LED alarm clocks all lose accuracy over time
Jeff Liebermann wrote in message
... On Sat, 19 May 2012 07:53:46 -0700, "William Sommerwerck" 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 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 |
#18
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 18:24:04 +0000 (UTC), "Geoffrey S. Mendelson"
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 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#19
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LED alarm clocks all lose accuracy over time
Jeff Liebermann wrote in
: On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms" wrote: I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...ital-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 |
#20
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LED alarm clocks all lose accuracy over time
"gregz" wrote in message ... "N_Cook" wrote: Bill Proms wrote in message ... I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...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. |
#21
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LED alarm clocks all lose accuracy over time
"Jeff Liebermann" wrote in message ... On Sat, 19 May 2012 07:53:46 -0700, "William Sommerwerck" 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. |
#22
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LED alarm clocks all lose accuracy over time
"N_Cook" wrote in message ... Jeff Liebermann wrote in message ... On Sat, 19 May 2012 07:53:46 -0700, "William Sommerwerck" 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 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 ............then some smart-arse invented the shaded pole motor. |
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 14:31:48 -0500, Jim Yanik
wrote: Jeff Liebermann wrote in 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? Neither. It was a junk RC oscillator. Just a resistor and capacitor. There was a reference designator on the PCB showing a ceramic resonator, but what was installed was a resistor and a capacitor. My replacement was a common 32KHz crystal that I found in my junk box. I suspect it's the latter.that would explain the poor freq.stability. You can trim up an XTAL oscillator. Ceramic resonators aren't all that horrible and can also be tuned. I've used plenty (usually Murata) for IF filters in radio designs at 455KHz and 10.7MHz. I will admit to matching them by frequency (bin test) rather than deal with tuning and tweaking. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 21:20:26 +0100, "Ian Field"
wrote: 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. There are plans all over the internet. Almost all of them use the Rockwell Jupiter board, which has a convenient 10KHz output. That would normal be the way to go, except that I have a large pile of Novatel Allstar 12 boards, which have 1Hz and 10Hz outputs. That makes the design somewhat more complicated. Its available as a kit, so although not particularly cheap it is fairly easy. Complete GPSDO modules can be found for about $300. http://www.navsync.com/GPS_timing.html http://www.navsync.com/docs/CW46_prod_brief.pdf I'm building mine much the same way, with integrated antenna, etc. The 1pps output can be used to run a digital clock, but I would hate to see the final cost. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#25
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LED alarm clocks all lose accuracy over time
Jeff Liebermann wrote:
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. -- Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379 In 1969 the US could put a man on the moon, now teenagers just howl at it. :-( |
#26
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LED alarm clocks all lose accuracy over time
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. |
#27
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LED alarm clocks all lose accuracy over time
"William Sommerwerck" wrote:
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 |
#28
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms"
wrote: I have 3 Intelli-Time LED alarm clocks around the house, just like the one he I don't think the LEDs are causing the problem. http://www.acurite.com/clock/alarm-c...k-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. |
#29
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LED alarm clocks all lose accuracy over time
"Bill Proms" wrote in message
... I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...k-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 http://www.ebay.com/itm/Westclox-700...em3cc5fe 675b or, if you want to see the display at night http://www.ebay.com/itm/Atomic-Proje...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 wris****ch. IMHO, If a clock doesn't show the correct time, its not a clock...its a timer. |
#30
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LED alarm clocks all lose accuracy over time
Jeff Liebermann wrote in
: On Sat, 19 May 2012 14:31:48 -0500, Jim Yanik wrote: Jeff Liebermann wrote in 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? Neither. It was a junk RC oscillator. Just a resistor and capacitor. There was a reference designator on the PCB showing a ceramic resonator, but what was installed was a resistor and a capacitor. My replacement was a common 32KHz crystal that I found in my junk box. I suspect it's the latter.that would explain the poor freq.stability. You can trim up an XTAL oscillator. Ceramic resonators aren't all that horrible and can also be tuned. I've used plenty (usually Murata) for IF filters in radio designs at 455KHz and 10.7MHz. I will admit to matching them by frequency (bin test) rather than deal with tuning and tweaking. an IF filter has a wider BW than what you want for an osc. Xtal gives a beter freq stability,because of it's sharper BW and high Q. you don't see ceramic resonators in freq. standards. Also,32KHz xtals aren't the best freq standards. 1-10 Mhz are the usual ones used for standards,better stability. -- Jim Yanik jyanik at localnet dot com |
#31
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LED alarm clocks all lose accuracy over time
"Ian Field" wrote in
: "gregz" wrote in message -september .org... "N_Cook" wrote: Bill Proms wrote in message ... I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...igital-alarm-c lock-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. radio alarm clock probably won't even use an xtal;like Jeff L. says,they may use a cheap RC osc. I note my MW oven clock that derives it's clock from line freq. has better stability than other "digital" clocks.(like my PC clock....) (of course,I use an internet program to keep the PC clock fairly close. I used to use a program(Atomic Clock) that direct-dialed the Naval Observatory,but the long distance calls cost too much.) -- Jim Yanik jyanik at localnet dot com |
#32
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 21:39:04 +0000 (UTC), "Geoffrey S. Mendelson"
wrote: Jeff Liebermann wrote: 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..... 1pps is one pulse every seconds. A second hand is quite common and useful. 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. I've watched several "wired home" type projects flounder and eventually fail. I'm still somewhat optimistic, but not much. One of my friends bought a refrigerator that's connected to the internet via wi-fi. http://en.wikipedia.org/wiki/Internet_refrigerator He thinks it's cool. His wife hates it and hangs a towel over the display. I saw much the same reaction as I watched the fully automatic microwave oven fail miserably. It's going to be a while before we have a wired (or wireless) home. 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. Not too expensive using a SONET GPS chip, which has a convenient 1pps output: http://www.analog.com/pr/AD9548 http://www.analog.com/en/press-release/6_11_09_Clock_IC_First_to_Harness_GPS/press.html For a commodity alarm clock, the chip does not need to be powered continuously. Wake it up a few times per hour, grab the time, update the alarm clock, and go back to sleep. A WWVB 60KHz clock is cheaper, but a GPS clock is "cool". Note that you do NOT need to see 3 or 4 birds. You need that if you want a lat-long-altitude position fix, but only one bird is needed for the time, which is sent by all the birds as part of the almanac. http://en.wikipedia.org/wiki/GPS_signals#Almanac However, I'd happily buy 5 or 6 of them with wifi. There are several SBC (single board computah) that will run Linux. Adding an cheezy dot matrix LCD display and running NTP is fairly simple. I'm tired of battery run analog or even line operated digital clocks ones that are off several minutes a week. Well, we could make a wind-up digital clock, but I don't think it will sell. I gave up wearing a watch long ago and use the clock in my cell phone or smartphone. Verizon (CDMA) keeps very accurate time. 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. It might have something to do with the internal construction. I'm running into the same mid-life mortality issues with cheap weather stations. The problem is that the old designs used discrete parts, SMT parts, and packaged devices. These days, the junk from China uses COB (Chip On Board) construction. The main chip is buried under a blob of epoxy or other goo. The epoxy has a different coefficient of thermal expansion as the PCB. It's not much, but over a fair number of thermal cycles, it will eventually rip the underlying chip apart. http://www.empf.org/empfasis/dec04/improve1204.htm Geoff. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 23:30:24 +0000 (UTC), gregz
wrote: 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. Heath AJ-1510. It may have been the first true digital synthesized FM tuner. http://www.fmtunerinfo.com/AJ-1510a.jpg I have one. Besides the keypad, it has 4 slots for preset frequencies which are programmed with edge notches on a 1x2" paper card. It's a good sounding tuner and was quite advanced in its day (1972-1975). 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. Weird. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#34
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 19:36:05 -0700, Jeff Liebermann
wrote: 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. Not too expensive using a SONET GPS chip, which has a convenient 1pps output: http://www.analog.com/pr/AD9548 http://www.analog.com/en/press-release/6_11_09_Clock_IC_First_to_Harness_GPS/press.html Oops. Bad choice of chips and much too expensive. This is more like it: http://geoffg.net/GPS_Synchronised_Clock.html Unfortunately, GPS boards are still rather pricy: http://www.sparkfun.com/search/results?term=gps+&what=products -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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LED alarm clocks all lose accuracy over time
On Sat, 19 May 2012 20:45:54 -0500, "Klaatu"
wrote: http://www.ebay.com/itm/Westclox-700...em3cc5fe 675b or, if you want to see the display at night http://www.ebay.com/itm/Atomic-Proje...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. 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 wris****ch. IMHO, If a clock doesn't show the correct time, its not a clock...its a timer. |
#36
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LED alarm clocks all lose accuracy over time
In article ,
Jim Yanik wrote: Jeff Liebermann wrote in : On Sat, 19 May 2012 08:51:38 -0400, "Bill Proms" wrote: I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...ital-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. ALmost certainly a crystal; ceramic resonators have way too much drift with temperature. 32 KHz crystals are very difficult to trim because they don't like to have any extraneous capacitance hung on them. Isaac |
#37
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LED alarm clocks all lose accuracy over time
In article ,
Jeff Liebermann wrote: On Sat, 19 May 2012 07:53:46 -0700, "William Sommerwerck" 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. When I was in college, (mumble) years ago, I built a 4-channel SCR light dimmer for the theater department. To my delight, the noise it put on the power lines would not only set the clocks, but also ring the bells. It was fun disrupting bridge games in the student union. Isaac |
#38
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LED alarm clocks all lose accuracy over time
In article ,
Jeff Liebermann wrote: On Sat, 19 May 2012 21:20:26 +0100, "Ian Field" wrote: 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. There are plans all over the internet. Almost all of them use the Rockwell Jupiter board, which has a convenient 10KHz output. That would normal be the way to go, except that I have a large pile of Novatel Allstar 12 boards, which have 1Hz and 10Hz outputs. That makes the design somewhat more complicated. Its available as a kit, so although not particularly cheap it is fairly easy. Complete GPSDO modules can be found for about $300. http://www.navsync.com/GPS_timing.html http://www.navsync.com/docs/CW46_prod_brief.pdf I'm building mine much the same way, with integrated antenna, etc. The 1pps output can be used to run a digital clock, but I would hate to see the final cost. Why use the 1 pps? Any cheap GPS you get on eBay will output NMEA "sentences" in ASCII that tell you the precise time. Just use those. Say, $15 for the GPS, another $15 for an Arduino, $5 for an LCD, and whatever crystal you have on hand, stuck in a home-made oven. Maybe another $20 for all the "glue", and the rest, as they say, is just software. Isaac |
#39
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LED alarm clocks all lose accuracy over time
In article
, gregz wrote: "William Sommerwerck" wrote: 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. The digital frequency synthesizer used for tuning was not exactly well-designed, but the tuner and stereo decoder part (which is what most folks actually wanted an FM radio for) was a real POS. Isaac |
#40
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LED alarm clocks all lose accuracy over time
Klaatu wrote in message
... "Bill Proms" wrote in message ... I have 3 Intelli-Time LED alarm clocks around the house, just like the one he http://www.acurite.com/clock/alarm-c...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 http://www.ebay.com/itm/Westclox-700...rm-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-Proje...61330?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 wris****ch. 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 |
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