Why & How
Why build an alarm clock? Why invest a lot of money and time in a self-built device? Where you can buy "normal" alarm clocks for just a few euros.
The short answer
First because it has features that no purchased device offers, and second because it's fun to build. See Assembly and Tests
- Time and alarm time can be read effortlessly and glare-free even in the dark; without glasses, without pressing buttons, without having to leave the right or left side position.
- The alarm clock can also be operated in the dark and with only one hand.
- A first-time user can operate the alarm clock simply by looking at the front. No need to read the instructions.
- It wakes you up with a pleasant, volume adjustable sound (MP3 song).
- It also works reliably in the event of a power failure.
- It is very accurate and independent of the reception of a radio signal, the mains frequency and the room temperature.
- It does not occupy any space on the bedside table.
- The alarm clock is mounted on the wall above the headboard of the bed.
- The display and control elements face downwards and are particularly large.
- Apart from the volume control, all elements are located on the front.
- The lettering is large and rich in contrast (black on white).
- Procedures like "Press this for 3 seconds and then 2x that ..." do not exist.
- The LED displays permanently show the time (red) and the alarm time (yellow), so there is no doubt even at night whether and to what time the alarm is set.
- They are individually dimmable. In addition, there is a tinted foil in front of them, so that you are not disturbed or even dazzled even in absolute darkness.
- The rotary knob switches to the setting mode for clock or alarm time. The hours and minutes can then be adjusted using the plus and minus buttons.
- Unintentional changes or deactivation of the alarm during sleep are excluded by using the switches as rotary switches.
- The alarm is triggered by an MP3 file (stored on an SD card and exchangeable), the volume of which can be preset.
- A snooze function is intentionally not included, as the alarm time can be easily and quickly set to any later time at any time.
- A USB battery pack provides the power supply. Normally it is charged and simultaneously delivers the 5 volts required by the Arduino. In case of a power failure it takes over the power supply (in my tests for several days).
- The real-time clock module is quartz controlled and also has a temperature sensor that corrects the gear speed depending on the room temperature. Thus a very high accuracy is achieved. Even if the 5-Volt supply by the Arduino is lost, the clock module continues to run with a 3-Volt button cell.