Digital Clock with an Analog Face.

Display Overview

• The inner LED ring shows the hour: yellow on the hour and green on the half hour. At 12:00, the indicator is blue.
• The outer LED ring shows the minutes in red. Every fifth LED is yellow, except at 12:00, where the indicator is blue.
• This clock does not display seconds.

Setting the Clock

Install three AAA batteries first. When the clock is powered on for the first time, it starts at 12:00. Set the time by advancing the display as you would with a mechanical clock.

There are three push buttons located between the hour LEDs near the 11 and 12 positions:

• SW1 – Minutes: Advances the minutes one step at a time. The hour indicator and half-hour position advance normally as the minutes progress.
• SW2 – Hours: Quickly advances the display so you can set the hour.
• SW3 – Zero Minutes: Resets the minute counter to synchronize the clock more precisely. You will not see any visible change when you press it.

Time.gov is a reliable source for accurate time information. For example, to set the clock to 3:15, start with fresh batteries so the clock begins at 12:00. Hold the Hours button until the display is close to 3:00. Then use the Minutes button to advance to one minute past the current time, and press Zero Minutes to reset the minute counter. When your time source reaches exactly 3:15:00, press Zero Minutes again to synchronize the clock. Using the Zero Minutes button is optional, but it improves accuracy.

Power

•  A USB-C connector is located at the 6 o’clock position for external power.
•  Use a USB-A to USB-C cable with a 5-volt USB charger that has a USB-A connector.
• The clock will not work with a USB-C fast charger.
• The three AAA batteries provide backup power. Use alkaline batteries to prevent the clock from losing time when it is unplugged.

Notes

• I installed new batteries in the clock on Wednesday, June 9, at about 1:00 p.m. I plan to run the clock on battery power only until the batteries are depleted and then report how long they lasted.

• I ordered five circuit boards from PCBWay, with one board assembled. The time from ordeing to delivery by DHL was one month.

• You can order the clock from PCBWay as either bare boards or a fully assembled unit, and the Gerber files are also available. I used red, green, yellow, and blue LEDs in my design, but you can choose any colors you prefer. If you want PCBWay to assemble the clock with different LED colors, you will need to update the bill of materials. If you like the clock and want to improve the design, download Other Files For Assembly Clock.zip. It includes all KiCad 10.0 project files. The ZIP file also contains ClockTemplate.pdf; print it at actual size to make a template for the four mounting holes located between 10 and 11, 1 and 2, 4 and 5, and 7 and 8.

• All parts should be available on DigiKey or Mouser. Except for the battery holder and USB connector Amazon is also a good option.

• Whether you order the clock fully assembled or build it yourself, you’ll need to mount it. Round boards from stores like Hobby Lobby or Michaels work well; I used a Round Acacia Wood Cutting Board from Woodpile Fun! at Hobby Lobby. For mounting, I used M3 12 mm standoffs, M3 20 mm screws, and M3 nuts, all listed in the component list. I drilled the holes using a small hand drill set from Hobby Lobby and an unused PC board as a template, then finished them with a Dremel. I also added round felt pads over the standoff screws to protect the wall. These are just suggestions, so feel free to use your own mounting ideas.