A simple little projector module for your DIY alarm clock 🕒✨
Building an alarm clock with a real wall projector is surprisingly hard.
Until now there wasn’t really an easy way to just buy a small module that can project the time cleanly.
So I went looking and found this cheap LED projector lamp on AliExpress:
https://de.aliexpress.com/item/1005009155662454.html
It’s super affordable, but it also has a few downsides:
- It’s a 7-segment display
- You only get 3 full digits
- The first digit is basically a “1” made from only two segments
- Plus the ":" in the middle
That said — the important part is:
✅ We only need the LCD, the rubber contact piece, and the lens from the projector.
Here are a few pictures from the project:
I designed a custom PCB using the HT1621 LCD driver, and the rest of the build is done with 3D printed parts.
All required files are included in this repository.
For a nicer final look, you can also add a small glass plate (20×1.5mm) from AliExpress:
https://de.aliexpress.com/item/1005003692263992.html
I also included a small Arduino test sketch so you can try it immediately.
Basic setup:
- Connect the module to your Arduino
- Add a small resistor for the LED
- Power it up and enjoy the magic 😄
If the image isn’t sharp, just twist the lens holder until the projection is in focus.
From my experience, the LED works best in darker rooms and projects clearly for about 3–4 meters.
It’s really important to use an LED with a 15° viewing angle, otherwise the projection will look weak or blurry.
These LEDs work great (I used them myself):
Green:
https://www.reichelt.de/de/de/shop/produkt/led_5_mm_bedrahtet_gruen_43300_mcd_15_-230982
Classic Red:
https://www.reichelt.de/de/de/shop/produkt/led_5mm_bedrahtet_rot_20000_mcd_15_-361605?nbc=1
Have fun testing and tinkering! 😄🔧