A while back (I think it was) EPE magazine (or might have been Elektor) published a GPS frequency standard generator projects.
Its available as a kit, so although not particularly cheap it is fairly easy.
They finally figured out the battery won't run the LED display for long and rigged it to blank during outages.
...........then some smart-arse invented the shaded pole motor.
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.
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 jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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.
Complete GPSDO modules can be found for about $300.
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 jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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. :-(
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 $400, without anyone questioning the price.
If Heath wants to come back as a kit company, it needs to design products that have no commercial equivalents.
Heath had an fm tuner with direct frequency entry push button. I never saw another for home use, but there may have been another or commercial use.
Around about 1974, bought my first led clock, and first calculator. The clock, cubo, from js&a was unique. Had separate buttons for hours, seconds, etc. You turned it upside down for snooze.
Greg
I don't think the LEDs are causing the problem.
If it's based on a quartz crystal, you could shave a little quartz off the big piece, or sand it off, or attach some more, depending on if the clock is slow or fast.
Just kidding.
or, if you want to see the display at night
I've used one of the projection alarm clocks for 4 years now, with the projector light on 24/7. No problems. Its has battery back-up, but no projection if the power fails. All the alarm and wall clocks in the house are now atomic. So is my wristwatch. IMHO, If a clock doesn't show the correct time, its not a clock...its a timer.
Jeff Liebermann wrote in news: snipped-for-privacy@4ax.com:
an IF filter has a wider BW than what you want for an osc. Xtal gives a beter freq stability,because of it's sharper BW and high Q. you don't see ceramic resonators in freq. standards.
Also,32KHz xtals aren't the best freq standards.
1-10 Mhz are the usual ones used for standards,better stability.-- Jim Yanik jyanik at localnet dot com
"Ian Field" wrote in news:9bTtr.549288$ snipped-for-privacy@fx07.am:
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
1pps is one pulse every seconds. A second hand is quite common and useful.
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.
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.
Not too expensive using a SONET GPS chip, which has a convenient 1pps output:
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.
There are several SBC (single board computah) that will run Linux. Adding an cheezy dot matrix LCD display and running NTP is fairly simple.
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.
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.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Heath AJ-1510. It may have been the first true digital synthesized FM tuner.
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).
Weird.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Oops. Bad choice of chips and much too expensive. This is more like it:
Unfortunately, GPS boards are still rather pricy:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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.
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
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
You can get short-term performance equal to a good crystal and long-term accuracy pert' near equal to the cesium beam clocks on the satellites for a whole lot less than that.
Start with a 10 MHz rock in a home-brew oven, and divide it down to make a "regular clock". Compare the time given by that clock to GPS time, and twiddle the crystal oscillator to make it track, using a very long time constant filter in the loop. The longer it runs, the more accurate it gets.
After it's run for a while, you can do without GPS updates for fairly long periods (depending on how good your oscillator/oven is) with very little loss in accuracy.
I've considered building that sort of rig where the oscillator's frequency is controlled by altering the temperature of the oven. The big advantage of doing things that way is that there are no extra paths for noise to get into the oscillator, as there would be if you used some sort of variable capacitor.
Isaac
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
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