GPS synchronized clock v1

GPS synchronized clock
Assumptions
- The clock shows the time with a resolution of 0.1 seconds and an error of no more than 50 ms
- Time is synchronized using a GPS receiver
- In the absence of GPS signal and disconnection of the main power supply, the time is maintained by the DS3231 clock
More information in the video.
Parts prices:
Ebay / Polish Allegro
LED matrix 8x32 2 pcs $5.10 / 49 zł
Arduino Nano $2.82 / 26 zł
DS3231 $1.38 / 14.65 zł
GPS+antenna $7.42 / 33.71 zł
Analog keyboard $1.91 / 10.71zł
Wires, connectors, box etc. $7 / 40zł
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TOTAL $25.63 / 174.07 zł

[@massimilianoamore6690]

Thanks for your reply. Could you suggest me a model of GPS receiver with PPS output. Regards Max

[@piotrne]

I have used a module similar to this one: www.ebay.com/itm/235123869115 . There are also modules without a PPS signal output to the connector. Probably this signal is available somewhere on the board anyway, but I bought a version with an openly available signal. The PPS signal is needed to precisely determine the beginning of a new second. NMEA transmission alone is not sufficient for this - it does not determine the precise moment of the second change. I used two quadruple LED modules as a display (8 modules in total). Please let me know if you managed to assemble the clock.

[@massimilianoamore6690]

Hello, Beautiful clock. Could you please share code & schematic ? Thanks Max

[@piotrne]

Hello, I will prepare the diagram and code for publication. It is now in prototype form and needs cleaning. The necessary elements are listed in the video, so you can buy them now :) The GPS receiver should have a PPS output.

[@piotrne]

I have shared the current, prototype and unpolished version of the project (connection description and code) here: tinyurl.com/GPSclock24

[@piotrne]

Hi Max, have you assembled the clock? If you have constant access to the GPS signal, you can slightly modify the program so that it synchronizes the time more often - not only at the user's request. In the current version, this only happens at the user's request and it is also possible to check the difference between the GPS time and the time maintained by DS3231, without synchronization. Such a check allows, for example, to detect whether a leap second occurred on the last day of June or December.