4 ms·
DCF77 also tells you what time it is, AC can only keep whatever time's been set in sync. The equivalent would be to include a 50-cent crystal oscillator instead
by mseebach 9y ago
DCF77 also tells you what time it is, AC can only keep whatever time's been set in sync. The equivalent would be to include a 50-cent crystal oscillator instead.
On a only barely related note, I've been playing with the idea of implementing a NTP synced clock on an ESP8266. It'd wake up, join wifi and sync NTP every few hours, then keep time on its internal crystal in between. It should be a good deal cheaper, work anywhere in the world, and have better indoor coverage (I have a DCF77 clock in an interior bathroom in London, and it never syncs. Kind-of defeats the purpose that I have to move it to a south-facing room for the day to get it to sync).
- pjc50 9y agoThe UI for entering the Wifi password is always the biggest problem with these things. The Dash buttons have an interesting solution involving audio.
- Drdrdrq 9y agoOne solution would be qr scanner...
- a1369209993 9y agoYou could try a USB SATA drive with a FAT16 filesystem containing "/wifipass.txt". USB-1.0 low speed is 1.5Mb/s and while I can't find documentation on ESP8266's GPIO switch speed, it's CPU is 40MHz, so bitbanging should be feasible.
- c3833174 9y agoOr just reporpose an old phone.
- mseebach 9y agoI was thinking about this in terms of building a product. Even with that, a clock generally runs for months, even years, on a single battery. Not exactly phone territory, but might be feasible on the ESP8266, depending on how the oscillator behaves in deep sleep mode.
- c3833174 9y ago>how the oscillator behaves in deep sleep mode. horribly
- sokoloff 9y agoThere are many dedicated real time clock chips, pre-designed for backup time-keeping and low power usage. Interfacing with one is going to be way faster/easier/better than trying to roll your own on a general purpose microcontroller, IMO. TI's bq32000 is $0.55@1K, is 3.3V for easy interface to the ESP, and takes just over 1 microamp in backup power mode. That's just one that I quickly poked at. (Side note: at this point, I'd think I'd want to be using an ESP32 in any new designs.)