Puzzlingly Simple Tutorial On GPS Time Corrected Clock

We’re not sure if [Derek Lieber] is messing with us or proving a point. Why are you doing this [Derek]? We know there’s technically enough information to build the clock. You even included the code. Couldn’t you have at least thrown in a couple of words? Do we have to skip straight to mediaglyphics?

Anyway, if we follow the equation. The equation… If you take a gps module, a 7 segment display with an HT16K33 backpack, a digital potentiometer, a piezo, and a boarduino we suppose we could grudgingly admit that these would all fit together to make a clock. We still don’t like it though, but we’ll admit that the nice handmade case was a nice touch, and that the pictures do give us enough details to do it ourselves.

It was also pretty cool when you added the Zelda theme song as an alarm sound. Also pretty neat that, being GPS corrected, there’s no need to ever set the time. We may also like the simplicity of the only inputs being the potentiometer, which is used to set the alarm time. It’s just. Dangit [Derek]. Nice clock build, we like it.

24 thoughts on “Puzzlingly Simple Tutorial On GPS Time Corrected Clock

    1. The rotary switch on the back is multipurpose.
      Press it and it works like a button.
      Turn it and it works like a rotary encoder (24 positions).

      – no press: turn it to set the brightness
      – short press, then turn it to set the alarm
      – long press, then turn it to set the timezone/daylight savings time

  1. Unfortunately, I cannot bathe in the sweet enlightening rays of GPS until I get about 20ft away from my house.

    (Yeah it’s a bastard for doing any testing. Multiple GPS devices have this prob for me, so it’s not just one bottle of weaksauce.)

    1. Hi,

      I bought an old serial (tomtom) GPS mouse for 10€ from ebay and

      actually, what I saw studying the serial output was, that indeed it needed a great time (1-3hrs.) to catch GPS coordinates when trying it indoors, however the time-fix needed just about 5-10 mins.

      Meaning: perhaps you expected it, to work faster, wait longer.

  2. That’s an encoder with push switch, not a volume control. Used for timezone, alarm time, debugging, etc. There’s also a serial port with menu.

    Basically, the “clock” displays the time output by the GPS receiver over I2C, adjusting for time zone (and possibly DST).

  3. I tried the GPS clock thingy and it wouldn’t work indoors. I bought 4 different GPS receivers and while some were better than others, none of them would even lock indoors. Some of them drifted really badly especially in the ‘Z’ axis.

    In the end I went with the DS3231 TCXO temperature compensated real time clock module that go for cheap on ebay.

    And did you see the WIRE-WRAP he used here lol. I revisited wire-wrap with a project that I will probably never finish, too many wire in a retro computer.

    BUT wire-wrap is perfect for when you have lots of modules that need to be connected together like this. 30 (or 31) gauge wire, wraps well on standard 0.1 inch pin headers.

    1. I designed and built a 2box gps system for my home. the general idea is that you have a ‘time beacon’ that is a gps receiver and an rf module of some kind (xbee or even hc05 or nrf). put the gps receiver where it gets signal and it will replay the contents (in serial ascii, etc) to your whole house. one benefit is that I pay for gps only once and all the rest of the clocks all just listen for periodic beacons.


      very small box and has been working well for over a year, so far. you can connect an external antenna, too, so that you get best reception.

      separating the gps part from the display was key and most people don’t think about that, it seems. you could also have ntp or other time sources feed into this and still the ‘beacon’ will transmit rf to the house and all clocks are auto-set. bonus: if your clocks are smart, you can broadcast messages and alarms in an IoT kind of way (no WAN leakage, though; I’m against that).

      1. I might give that a go. Perhaps a GPS module, ESP8266 or small radio, small solar cell and LIPO battery and stick it on the roof or something. It would have the added advantage of always knowing where the house is.

        1. If you have a fixed GPS unit you can average the location data over time and broadcast the difference between that average and the current signal to boost the accuracy of any nearby mobile GPS devices that can receive the differential data signal.

          And if you do do that you should expect your house to suddenly “move” about 1.5 early next year, so make sure your code can handle it.

        1. I don’t think the suggestion was necessarily to use an RPi, just that using GPS as the clock source for an NTP server is more useful than multicasting the time by some custom protocol. I could be wrong though.

    1. gps receives well for many of us (the others, not as much). gps receivers with ttl serial are $10 and even less. what’s not to like?? its not $100 anymore and so gps can be everywhere you wanted but could not justify it before. I use ublox neo-6 (and up) series. great stuff and simple NMEA. again, what’s not to like at this price?

    2. My clocks that set themselves from WWVB have trouble getting signal indoors. I’ve considered making a GPS clock that drives a very low power transmitter simulating the WWVB signal.

  4. Q: Why GPS?
    A: its cheap, you can find gps receivers for example in UMTS-mini-pci-e cards, that work out of the box without a sim card,
    and you can connect it via USB
    – serial gps receivers are enmass on ebay

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