What is it?

Features

(All boards are now Rev 1.0A with mostly SMD components.) This is an accurate GPS corrected clock, with 4 large 1.8" LED digits. The clock depends on GPS data to continuously adjust itself. Without GPS, it can also be operated as a normal clock. The on-board real time clock (RTC) will also hold the current date. Accuracy is <0.2s (as benchmarked against TIME.IS website). You can see the video here

Summary of features

• Uses USB 5V supply (draws only 120mA typical running condition). Runs off power bank, laptop, mobile phone chargers, etc.
• Set and forget. GPS will do the rest. Set the time zone only once and it will be stored in memory. Correct time, every time once valid GPS is obtained. No need for backup batteries.
• Satellite count shows the number of satellites in use. Use this to determine the best location to place the GPS antenna for the highest number of satellites.
• Auto dimming display with night mode. Use it anywhere, and get the ideal display brightness at all times.
• Date display every 20 seconds (can be disabled to just show the time).
• Date format to be displayed can be set (MM:DD or DD:MM).
• Auto input selection (direct GPS connection or through the GPS RF module (optional)). No setting needed, as you can switch between either mode with just 2 simple steps.
• Indicator LEDs show communications and GPS Fix status. Quick visual indication of what is happening with the clock.
• With the optional RF module, you can have multiple clocks sync to a single time source. This allows scalability and expansion.
• 12 / 24 hour display mode with AM / PM indicator.
• 1 touch Daylight Saving Time mode. Manually switch between DST and normal time with 1 button press. Activating DST adds 1 hour to the current time.

Video on how to set the clock is here.

RF Transmitter Module

RF wireless data streaming of GPS data is an option. This works very well if the GPS antenna cannot be positioned in an optimal location due to the placement of the clock (GPS antenna's cable length may not be long enough). In this case, there is an optional GPS RF (2.4GHz) transmitter module available. Since the clock already comes pre-built with the RF module on board, you only need to purchase the GPS RF transmitter module. The GPS RF transmitter module can be placed in a convenient location for the GPS antenna placement, while allowing the freedom to place the actual clock somewhere more suitable. If you get the optional RF transmitter module, additional clocks can be purchased and synced to the module wirelessly. I have 3 clocks syncing from the GPS RF transmitter module and the video is here.

You can even have multiple clocks showing different time zones around the world, in perfect sync!

Running the clock without GPS correction (free running) is possible with the on-board RTC. However, its time accuracy will drift, as it is solely dependent on the RTC's own accuracy. The RTC has a built-in calendar which allows the date and month to be displayed.

Why did you make it?

After many years of using a battery driven clock in the bedroom (that seems to get slower even way before the battery dies), I had a mission to build something that is accurate and suits my needs. I wanted a battery free design, accurate and hassle free to use. This clock is the result and it has met all of those needs.

What makes it special?

It is accurate, flexible, highly featured, practical, easy to use and scalable. It has that raw look, but at the same time quite eye catching with the multi colored LEDs. Purchase the optional GPS RF transmitter module and you can add on as many "slave" clocks as you like! This clock uses a Microchip PIC microcontroller, and the board is ready with the 5 ICSP programming pins. You can write your own code and flash it to the onboard MCU or flash new firmware if I have new ones available.

More write up and files on Hackaday IO

Operating manual will be provided upon purchase.

Note: There are 2 slightly different designs of the clock board. One design has rounded PCB edges and the other has angular PCB edges. Both are functionally identical otherwise.