This is an arduino-based clock using a 7219 dot matrix display:
https://www.amazon.com/Wangdd22-MAX7219-Arduino-Microcontroller-Display/dp/B01EJ1AFW8
This is an alarm clock based on a traditional bedside alarm clock. It supports setting time, setting an alarm, displaying seconds, and changing brightness. It supports a backup battery source, 3 AA batteries, to get a user through the night should the power go out.
Clock is based on the DS3231 RTC:
https://www.amazon.com/DS3231-AT24C32-Precision-Module-Arduino/dp/B01IXXACD0
The clock stores the set time in the RTC and reads the time from it. It uses an interrupt from the RTC to read every second, rather than continually polling to see if the time has changed. It also writes the time to the dot matrix display and then does not rewrite that minute or hour until a change occurs.
It does not support 24-hour time. It does not support date even though the RTC can handle that. I don't want to add more buttons for either of these functions. Plus no traditional bedside alarm clock I used growing up (the classic red-glow, 7-segment, fake-wood clocks) had these functions, so I'm not motivated.
The RTC supports two alarms but I only support one. The second alarm is used in the implementation of snooze.
- Show time from an RTC
- Show seconds upon button push
- Set the time using time set, hour, and minute buttons
- Blink separator
- Set an alarm
- Have alarm trigger a buzzer
- Snooze
- Support changing brightness
- Backup power (RTC has time backup already, this is for the display and alarm to still work)
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Show temperature?- I added this functionality and the temperature was impressively off. Other thermometers in the same space were saying 72 or 73 degrees F and the RTC was saying 66 degrees F. Why even add the feature if it's that unreliable.
- Build an enclosure