I've always been interested in radio and timekeeping. I'm an amateur radio operator, and we often tune in WWV (or here in Canada, CHU) to tune and test our radios and antennas. They broadcast the time using both voice and data in the HF range. However, there is another more powerful and much simpler system, run by many countries around the world: longwave time! WWVB in the US broadcasts on 60kHz(!) with an effective radiated power of 50kW, covering most the US during the day and propagating all over at night. Japan and Germany also provide longwave time signals on different frequencies (so make sure you order the right version of the kit for your particular region!).
Soldering the kit was easy (and it coincided with my switch to lead-free soldering, so this was a good test). I got it hooked up to a random Arduino I had laying around. There's a few different implementations, and of course you can implement a basic library from scratch, but for a quick test I just grabbed one of the suggested projects and stripped out all the RTC and display code, to just the bare decoding and serial display code. During the day where I live, it's a bit marginal (though this is expected) but during the night the reception is quite good. I was able to decode the time and date easily!
This is how all those "atomic" self-setting clocks work. It's kind of funny that they call themselves "atomic" as of course there is no atomic clock inside them; rather, they are just picking up WWVB which is calibrated by an atomic clock. But, the uncertainty is quite low, and this board would be great in any project that needs reliable time data but doesn't have room or power for a constantly running GPS module. The chip this uses (the MAS6180C) consumes well under 100uA when actively receiving and decoding. It has a convenient power-down pin, which drops the consumption to 100nA when activated. Of course, as the seller suggests, if you need it to be low-power you need to remove the LEDs, as they draw more current than the rest of the circuit! But they are great for debugging, and to see if it's outputting data or not.
Remember that in consumer products which use this type of chip, the designers have done all the hard work of carefully placing the antenna, and optimizing their code to get the best results. As this is just the receiver module, *you* now need to do a bit of work to position the antenna correctly, ensure it's away from high-speed digital circuits, etc. But with a bit of care you can get excellent results. Very cool board, and great fun too!
Response from Universal-Solder | July 16, 2022
Thank you for the nice review. BTW, the LEDs do not have to be "removed" to turn them off. There is a jumper "LED" on the board. Just cut the trace between the pads to turn the LEDs off. A drop of solder, placed between the two pads, will turn them on again if needed.