When I was little, I used to have a projector alarm clock in my bedroom. It is convenient to wake up in the middle of the night and be reassured that you have 4 more hours of sleep, just by glancing at the ceiling. A few years ago, I set out with the idea to make a DIY version of said clock, but a little bit more useful. First, I searched for previous attempts at making a DIY projector: I found the awesome work by Thomas Pototschnig. He documented every aspect of the build, from the lens system to the custom PCB he designed. The image quality is very good, but the total price was too high for my taste, so I discarded the project until a few months ago.

Random Aliexpress finds

The turning point was finding the cheapest projector I could find on Aliexpress. For a little bit more than 3€ you get a lens array, an LED, a pcb with a battery and usb-c charging. These kind of projector usually have a translucent moon slide to insert between the lens array.

On Aliexpress you can also find very cheap IPS 0.96 inch SPI displays. My idea was removing the backlight of said display and insert it in the lens array instead of the moon “projection chip”.

The final result

I designed the external case in Fusion 360 and 3D printed it. The LED is a White 6500K 3W 3535 mounted on a 16mm aluminum PCB. I also added a larger heatsink, but the LED runs at very low power, thanks to a cheap constant current driver. The focus is adjustable via a threaded housing for the projector lens. A photoresistor acts as a light sensor: when the room is bright, the LED automatically turns off. Everything is controlled by an ESP32-C3 board, powered by a USB Type-C cable. The ESP32 runs a modified version of G6EJD’s e-paper weather station code. I adapted it to display the time, date, and current temperature and humidity. The weather data is updated every 10 minutes, after which the board disconnects from Wi-Fi. Since the screen is a color LCD, it can also display different colors, although the individual RGB subpixels become more noticeable with such magnification. The total cost of this projector is around 17€, slightly more than just the lens used by Thomas Pototschnig.