WWVB radio controlled clocks

[Smucky]

Man this stupid hacker news post got me going down a rabbit hole for radio controlled clocks. I always knew the tech existed, but never really looked into how it worked. For some reason once I learned that it was broadcast from only one antenna in Colorado, it awoken my inner autist. Dug around through the random online SDR sites and found one that could tune well enough to 60khz (vid below). A wall clock supporting radio time can be had for under $30 now. But I think I'll go the cheap route and just buy the movements and swap them out. Except they are all of out stock as of right now with an ETA of two+ weeks Anyway, guess that will be my next project.

On a practical sense, I can see why this never really caught on. With either movement, you are going to be replacing batteries every 12 months or so. Even the cheapest movements will only change +-1 minute over a year. So you just change the battery and set the time, and you're good. Versus with a radio clock, you change the battery and then don't have to set it (but it probably won't find the radio signal until night when interference is lower) So yea, kind of a gimmick. But I think I'll jump on it

wwvb_20240604.mp4

[Smucky]

All my money go to china

[Smucky]

Bought a chinese receiver to play with. I'll need to sacrifice one of my kids toys so I can add an led or something to it so you can watch the timecode blink out

Screenshot_20240612_141534.png

[Smucky]

But customs taking forever

Screenshot_20240612_141625.png

[NinjaPoodle]

Why are you nerding about this nonsense?

Also how do you set the time zone?

[Smucky]

Hmm, now "klockit" showing they are back in stock but that page doesn't show up anywhere on their site. Got the direct link from google. And price is about half of everyone else Wonder what that means Should I spend $100 on a bunch of movements before I can verify with my chinese receiver if I can even get the signal?

[Smucky]

I'm thinking yes

[Smucky]

Why are you nerding about this nonsense?

I have autism

Also how do you set the time zone?

There's a button

[Smucky]

Just bort yolo

Screenshot_20240615_130245.png

[NinjaPoodle]

$0.00 is a good price.

[Clockwork]

Radio controlled cocks.

[Smucky]

[Smucky]

I got the toy receiver in the mail today. Will mess with it later. Need to fine an led I can wire in so it will blink.

PXL_20240618_193445397.jpg

[NinjaPoodle]

That dildo thing looks pretty beat up. Are you sure someone hasn't used it before you?

[Smucky]

Strangely the outside plastic envelope was dry. But the inside ziplok bag had some sort of moisture inside

[Smucky]

Got it breadboarded. But then discovered that led's won't actually light up unless you put more than 2 volts to it. So need to add another battery. The other weird thing is the output starts pulsing what looks like the timecode as soon as the battery is applied. Seems like it should take a few minutes to sync. And the receiver on/off pin doesn't seem to control anything

PXL_20240618_233301855.jpg

[NinjaPoodle]

What are you trying to achieve?

[Smucky]

What are you trying to achieve?

I think I explained everything in my first post? I bought some replacement radio controlled quartz units to swap out the guts of four of my wall clocks inside. But also bought this cheap china receiver to play around with. Originally I just wanted the antenna because I was going to attach it to my laptop's microphone input and sample it at 192khz to see if I could pick up the 60khz wwvb signal. Sounded fun, but I lost interest so once the receiver came in, I just wired it up with the idea to see if there are any "dead" areas in my house where the signal wouldn't deeply penetrate.

I added three volts to the total power so now the LED will light. Also the receiver does work, I was apparently just getting really good reception yesterday when I first tried it. It is raining today and that seems to hurt. It is certainly susceptible to interference. Notice in the video at 1:50 as I get the camera closer that causes the LED to flicker more. It is also very much directional, as in the video I lastly rotated it 90 degrees and you can see the LED flickers even more.

I'm going to try to decode the flashes here later into the binary. That is funner than actually doing what I am supposed to be doing at $work. It should decode to sometime around June 19 2024 @ 19:30 UTC

PXL_20240619_192754155.TS_720.webm

[Smucky]

Ok, took longer than I thought, but was easier than I thought. Per the docs the "timecode" is a series of high/low amplitude pulses each one second in duration. At the beginning of each second, amplitude starts low. If amplitude increases after 200ms, this is a 0 bit. If amplitude increase after 500ms, this is a 1 bit, if amplitude increases after 800ms, this is a "marker" bit. I basically took the video file and converted it to the raw frames. Then I increased the thumbnail size of my file browser until about 30 or so thumbnails could fit on the screen. This gives a nice picture of one second of time. From there it is easy to see if the LED is on for a long duration (0 bit), equal on off time (1 bit) or off most of the time (marker bit) as seen in the screenshot below. The video starts with the LED on, so I threw out the first few frames until the LED is off. And as you can see, for six frames it is off, then on for a longer duration. It turns off right around frame 30.

Screenshot_20240619_204254.png

[Smucky]

So from that position, what we have is long duration, long duration, equal duration, long duration, equal duration, equal duration, marker duration, marker duration.

Or in the binary notation:
0 0 1 0 1 1 M M

So after just 9 seconds in the video, we already see two "marker" bits. That signifies the end of one frame, and the start of a new frame. How lucky!

[Smucky]

So lets continue at that last marker:

M 0 1 0 0 1 0 0 0 M 0 0 0 1 0 1 0 0 1 M 0 0 0 1 0 0 1 1 1 M 0 0 0 1 0 0 1 0 1 M 0 0 0 0 0 0 0 1 0 M 0 1 0 0 0 1 0 1 1 M

One "frame" is 60 bits, taking 60 seconds to transmit. And since the video is nearly two minutes long, we got part of another one:

M 0 1 0 0 1 0 0 1 M 0 0 0 1 0 1 0 0 1 M 0 0 0 1 0 0 1 1 1 M 0 0 0 1 0 0 1 0 1 M 0 0 0 0 0 0 0 1 0 M

It got cut off due to the interference at the end of the video. For the first frame, I had to make a "best guest" once. For the second frame, I had to make a "best guest" about three times before giving up. So not sure if a microchip would have been able to synchronize or not with the first frame.

As you can see, there is just one bit difference between the two frames as they are just one minute apart.

[Smucky]

Lets try to decode the first frame. There is a cheat table from the docs

Screenshot_20240619_211658.png

[Smucky]

So we can just copy each row and fill it in with our data

Code: Select all

Marker min_40 min_20 min_10 0 min_8 min_4 min_2 min_1 Marker
M         0      1      0   0   1     0     0      0    M

Add that up and we get 28 minutes

Code: Select all

0 0 hour_20 hour_10 0 hour_8 hour_4 hour_2 hour_1 Marker
0 0  0       1      0   1     0       0      1       M 

Add that up and we get hour 19.
Our date is give by a "day of the year" counter which takes up two rows:

Code: Select all

0 0 day_200 day_100 0 day_80 day_40 day_20 day_10 Marker
0 0    0      1     0    0     1      1      1      M

day_8 day_4 day_2 day_1 0 0 UT1_S[2] UT1_S[1] UT1_S[0] Marker
   0    0     0      1  0 0    1       0        1       M

Add that up and we get 171. The UT1 stuff is for leap second correction, so ignore.
The last two digits of the year also takes two rows, plus more leap second stuff to ignore:

Code: Select all

UT1_C_0.8 UT1_C_0.4 UT1_C_0.2 UT1_C_0.1 0 year_80 year_40 year_20 year_10 Marker
  0           0        0        0       0     0     0       1       0       M
  
year_8 year_4 year_2 year_1 0 LYI LSW DST[1] DST[0] Marker
 0       1      0     0     0  1   0    1     1      M

Add up the year bits and we get 24.

So fully formatted we got 19 hours and 28 minutes UTC. 171 days = June 19 in the 24th year, or:

June 19, 2024 19:28 UTC

It works

[Smucky]

Looks like I just spent three hours on this
Guess I need to go to work now

[Smucky]

The radio controlled quartz units should be here tomorrow so I'll swap a clock or two out tomorrow. They should be able to receive the signal fine as they all ironically face Colorado. The one in my daughter's room does not though, so not sure if I'll be able to convert that one. Three out of four ain't bad though. This feels so futuristic