Color 7-segment display

still from movie

The goal of this project is to create an alarm clock which can indicate by digit-color, how soon the alarm will go off. This means you don't have to wake up to interpret the meaning of the numbers, but just enough to associate a color with 'it is safe to go sleep again'.

Click om the image above for a short movie. The project is not yet complete, but this is a first presentable state.


base board

The base board contains a PWM Servo Driver, here used just as I2C demultiplexer and MOS-FET drivers for the seven combined cathodes for a color. The PWM here comes from the Arduino. A base board is connected to two digits, here just one is connected.

back side of digit

The 3D-printed digit / LED holder has 7 LED sized holes at the back and 8 square holes to save filiament. The first few layers are black, most of the digit is white. The square holes could be filled with black paint to reduce bleeding between the segments. The digits could be made out of complete black filiament, but then we would loose internal reflection too.

The current prototypes are not very experiment-board friendly, as the LED distance is not properly aligned.

digit wiring

The wiring here is all segment anodes separate and the color specific kathodes combined, giving 7 + 3 wires. What is missing is the schematic. This is not yet in a presentable form. The hardware for thje other two digits, the baseboard and the RTC interface have to be build and programmed.

By the way, if you want a RGB-7-segment LED display ready for a finished product, you better look at

Last update: 2017-03-24