Transparent arduino alarm clock

Dec 06th, 2019 | by: Simon Cornu
Category: Electronics Basic Circuits

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This is not my first project but it is the one I enjoyed the most. It is a simple alarm clock but I wanted an original way of turning it off. Therefore, to do so you need to turn it upside down ! And I also wanted to make it transparent, in order to see the internal. I think it's a shame to hide all the beauty of electronics.

I will not make a tutorial to explain how I made it but here are some details:

The time is obviously handled by an RTC module (the classic DS3231);

I store the sounds on a SD card, so there is a SD card reader module;

The sound is amplified by a single transistor (I don't need a loud noise to wake me up) and emited by a loudspeaker of 55mm in diameter;

There is a battery in case there are no plug nearby (I don't know its capacity, I salvage it somewhere some time ago). So I also added a charging module and a step up module to have a constant 5V;

The display is composed of a 4 digits-7 segments display and I drive it thanks to a single SN74HC595;

To detect the orientation, a simple yet efficient tilt sensor is used (the one with a little metal ball inside a tube, debounced with an usual little RC circuit);

There are 2 buttons at the back to setup the arduino and a power switch;

To handle all this input/output, I use an arduino nano. Its main routine is the display since I only light up only one of the four digits at a time. I've removed the 5V regulator since I don't it and to save power. I also removed all LEDs on each module because it is annoying and wastes power. I've only keept the LEDs from the charging module.

And because the arduino and the LED display were quit energy intensive, I added a low power mode with the LowPower library. When this mode is activated, the time is not displayed and the arduino wakes up only when the orientation changes or when the alarm should be activated. So it can run for a few days.

And to make it transparent, I use acrylic sheets. 5 sides are glued together and the last one (in the front) is maintain with 4 bolts and nuts. This part was the most complicated ! And I'm not so happy with the result, the glue I was using left some horrible white marks...

I think I've said everything about this project!

PS : English is not my native langage, sorry if it doesn't sound natural