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[#] Sat Nov 09 2019 19:02:33 EST from zooer @ Uncensored

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Precision Clock, works with GPS.  It has no controls.

Kits available on the website.  


[#] Sun Nov 10 2019 17:08:26 EST from zooer @ Uncensored

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Or you can simply order clock from Heathkit!*

Fran demonstrates how it (sort of) worked.


*No you can't simply order one of these from Heathkit

[#] Tue Nov 12 2019 17:18:15 EST from IGnatius T Foobar @ Uncensored

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Yup. I've seen that video. Not willing to spend 100 GBP on a kit when what I really want to do is design and build from scratch. But he's got the same mindset -- build a clock that has no controls and cannot be set manually.

[#] Tue Nov 12 2019 19:48:33 EST from zooer @ Uncensored

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I think he offered a kit but provided the schematic for free on the website.  

[#] Thu Nov 14 2019 10:49:25 EST from IGnatius T Foobar @ Uncensored

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Yup. His design is pretty good. Once you get the basic concepts, though, the design starts to become obvious. There are basically two ways to do it.
If you want to drive the displays manually, you put in a bunch of shift registers and bit-bang the segments. The other way, which is much simpler, is to use a driver chip like a MAX7219 which handles the multiplexing of up to 8 digits x 8 segments on its own, and you just send serial data/clock to it from your microcontroller's GPIO pins.

I have a four-digit display (with huge 1.2" LED digits) and a driver chip.
At this stage of the build it's displaying a free-running software clock.
The accuracy is terrible, but since I will be picking up WWVB all day long it's not an issue. I could always toss in an RTC if I wanted to, or even go back to my original idea of using the 60 Hz AC power as a timing source.

In the future I want to build a GPS driven clock as well, but that one will have a 16x2 LCD display.
Surprisingly, nearly all LCD text displays use the exact same interface, based on the Hitachi HD44780 controller. I'm thinking that one will probably be built on a Raspberry Pi instead of an Arduino, so it can be attached to Ethernet and used as an NTP server.

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