Shop OBEX P1 Docs P2 Docs Learn Events
Self setting Alarm Clock — Parallax Forums

Self setting Alarm Clock

CassLanCassLan Posts: 586
edited 2009-03-10 05:21 in General Discussion
Hello all,

I have a $25 Alarm clock...nothing special...AM/FM Radio...etc. (GE is the Brand)

When you plug it in it automaticly sets the correct date and time, it does this within 2-3 seconds.

The only thing I can think of is that it either gets it from some signal in the AC current?? Or that since it has a radio builtin its tuning into some local time frequency.

Does anyone know how this works?
Has anyone ever built this functionality into the propeller with a RTC??

Thanks,

Rick

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-03-08 17:26
    There's an atomic clock in Boulder Colorado attached to a radio transmitter that continuously transmits the current time and date on several frequencies in both digital format and recorded voice. Various "self-setting" clocks and "atomic" clocks have a simple receiver and decoder for this time standard signal. It could certainly be done with a Propeller with the appropriate receiver attached to the Propeller. As far as I know, it hasn't been done yet.

    Here's one company that makes decoder chips: www.c-maxgroup.com/tech/history.php
  • CassLanCassLan Posts: 586
    edited 2009-03-08 17:31
    Thank you Mike,

    I will look into this to see if it fits my project, if it does I will upload code.

    Rick
  • mctriviamctrivia Posts: 3,772
    edited 2009-03-08 17:50
    does anyone know what the range on these towers are? can you receive in most of canada and US?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • CassLanCassLan Posts: 586
    edited 2009-03-08 17:52
    Looks like it mctrivia:

    http://www.c-max-time.com/tech/wwvb.php


    Rick
  • kwinnkwinn Posts: 8,697
    edited 2009-03-08 17:56
    mctrivia, I have a clock that does the same thing and have no trouble receiving a signal where I live (Brampton, ON).
  • mctriviamctrivia Posts: 3,772
    edited 2009-03-08 17:56
    it says receiving area is the smaller circle. so I guess not

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • mctriviamctrivia Posts: 3,772
    edited 2009-03-08 17:58
    kwinn does it use the atomic clock or cell towers? I have one that uses the cell towers and will get correct time and time zone as long as there is cell coverage.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • Mike GreenMike Green Posts: 23,101
    edited 2009-03-08 18:21
    mctrivia,
    Have you looked at the animated display of the reception area? It shows the area covered vs. time of day.

    A receiver for the time standard signal (WWVB) is much simpler (and cheaper) than one for cell phone frequencies. I was not aware that you could get the time from the cell phone network with anything other than a cell phone (or equivalent module).
  • TreeLabTreeLab Posts: 138
    edited 2009-03-08 18:24
    The link provided by CassLan shows a range of 2000 km, which would disqualify most of us. The link to the animation shows a time-dependent coverage that extends much further (especially to the south east), presumably due to high-altitude ionization effects. By my eye Quebec get very poor direct radio coverage.

    Cheers!
    Paul Rowntree
  • mctriviamctrivia Posts: 3,772
    edited 2009-03-08 18:27
    also looks like BC and Alberta gets pretty poor coverage.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • JonathanJonathan Posts: 1,023
    edited 2009-03-08 18:38
    I used to use WWVB, but I got reception only at night. Then when that unit broke, I got a cheap Motorola Oncore II OEM GPS module. The GPS works great and locks onto the time fast. I use it to TX the time locally, so all of my projects and clocks are on the same timebase. I woke up this morning and all the clocks in my house had the right time. [noparse]:)[/noparse]

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    www.madlabs.info - Home of the Hydrogen Fuel Cell Robot
  • mctriviamctrivia Posts: 3,772
    edited 2009-03-08 19:14
    obviously you have code to compensate for day light savings time. GPS does not. Thankfully. I use GPS UTC time stamps for keeping things in chronological order even as I travel from time zone to time zone and pass of day light transitions.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • JonathanJonathan Posts: 1,023
    edited 2009-03-08 19:45
    Yup, I have code dealing with DST. I'm not a fan of dst, when the sun is overhead, it's noon as far as I am concerned, time zone adjustments excepted of course.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    www.madlabs.info - Home of the Hydrogen Fuel Cell Robot
  • Carl HayesCarl Hayes Posts: 841
    edited 2009-03-08 20:34
    One general solution, as mentioned, is use of a GPS receiver, which works anywhere on Earth except inside most buildings, which shield the GPS signal.· But it should be easier to get time than position -- for time you need to hear only one bird, while for position you need several.· GPS birds will tell you the time several times per second.

    The use of cell-phone signals is an interesting solution, but technically illegal.· In the US anyway, interception of cell-phone signals for any purpose is unlawful unless you're either the caller or the receiver of the call, or are intercepting for regulatory or law-enforcement purpses, or you are the cell-phone provider (the cell-phone company).· Also, they transmit the time only at the start of a call (but a cell tower initiates calls pretty often, I guess).

    WWVB signals are useful throughout most of North America, but in most places they can be received only at night, and some kinds of ·buildings shield the signal, preventing reception.· They're also hard to receive in the presence of electromagnetic noise such as that from digital electronics.· They include handy encoded information giving time, date, and even a bit that indicates DST.··It can take many hours to acquire time information by WWVB, especially if you start·during daylight hours when you can't hear it at all.·

    Since your alarm clock sets itself within a few minutes, I'd bet it's got a GPS receiver in it.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    · -- Carl, nn5i@arrl.net
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-03-08 20:57
    Carl Hayes said...
    The use of cell-phone signals is an interesting solution, but technically illegal. In the US anyway, interception of cell-phone signals for any purpose is unlawful unless you're either the caller or the receiver of the call, or are intercepting for regulatory or law-enforcement purpses, or you are the cell-phone provider (the cell-phone company).
    Although it's strictly illegal to monitor actual cell phone calls, there are other services available via cell phone providers. For example, I have an Ambient Devices "Wireless Weather Forecaster" that intercepts five-day weather forecasts over cell frequencies and displays them on its LCD, without having a cell account or paying a monthly fee. So it's not unrealistic to imagine that time and date might also be available as a similar service.

    -Phil
  • JonathanJonathan Posts: 1,023
    edited 2009-03-08 21:08

    Since your alarm clock sets itself within a few minutes, I'd bet it's got a GPS receiver in it.
    Wouldn't suprise me either. It used to take my WWVB unit a while to connect, and in bad atmospheric condition, it could take days to synch. I do live in a poor reception area though..

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    www.madlabs.info - Home of the Hydrogen Fuel Cell Robot
  • virtuPICvirtuPIC Posts: 193
    edited 2009-03-08 21:33
    TEMIC produces U4224B - a chip that demodulates the time signal from RF to serial. Look at the data sheet to find several transmitter stations worldwide. They transmit on frequencies below 100 kHz with different modulations. I know best the German station DCF77.

    Frequency is 77.5 kHZ, each second has a drop of amplitude to 20% of 100 ms or 200 ms duration meaning 0 and 1. There is no drop at the 59th second of each minute. Encoded is time at second resolution with date including year number. And yes, DST is supported and leap seconds have warnings. They also use a phase modulation which is more robust to transmission distortion. Oh, by the way, the different range is due to different ionospheric conditions and resulting mix of ground wave and reflected wave. Here in Germany you can buy small receiver modules for a few Euros demodulating the RF and giving the binar stream of 100 ms / 200 ms pulses to be decoded by a UC.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Airspace V - international hangar flying!
    www.airspace-v.com/ggadgets for tools & toys
  • mctriviamctrivia Posts: 3,772
    edited 2009-03-08 21:40
    leap seconds is an interesting fenomina. just a note. GPS does not accommodate for leap seconds though earth based error correction towers I believe do transmit the offset because of leap seconds.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Need to make your prop design easier or secure? Get a PropMod has crystal, eeprom, and programing header in a 40 pin dip 0.7" pitch module with uSD reader, and RTC options.
  • kwinnkwinn Posts: 8,697
    edited 2009-03-08 22:04
    mctrivia, I am not sure if mine uses cell towers or some other signal. It was a $9.99 clearance item at Radio Shack a year or two back and had no box or manual. It seems to work well and the batteries last a long time. Mostly used for setting the various clocks around the house after a power outage. The brand is Centrios and it says Atomic on it. It automatically set the time ahead an hour today.
  • Mike GreenMike Green Posts: 23,101
    edited 2009-03-08 22:11
    kwinn,
    I have one of the same units. It has a receiver inside for WWVB. Pretty much anything that says "atomic" works the same way.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-03-09 19:35
    This thread is being moved from the Propeller Forum to the Sandbox forum.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Engineering
  • dMajodMajo Posts: 855
    edited 2009-03-09 19:52
    There is also other chips and modules
  • dMajodMajo Posts: 855
    edited 2009-03-09 19:59
    ?!? Where is my post

    It was "There is also other chips/modules"

    @Chris,
    looks that I was posting while you was mooving the thread. The new location showed my as last poster but the post disappears
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2009-03-10 05:21
    Between the decoder chip that Mike mentioned, and an RF antenna that DigiKey sells you would be pretty set if you live within the transmitter area.
    Hooking this antenna right up to the scope, I was able to pick off a 150mV signal. I originally had purchased two of these coils with a notion to apply
    them to a Propeller self-setting clock application, but never got around to it.


    search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=561-1001-ND
    CMA-60-100.jpg

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.

    Post Edited (Beau Schwabe (Parallax)) : 3/10/2009 2:51:44 PM GMT
Sign In or Register to comment.