Clock - gold&silver

IoT clock


Design and construction of a clock that serves the university. The idea is to design a clock that can display the occupancy of the classrooms.


The clock picks up the iCalendar data of the room occupancy of the "Forum Gold&Silber" and can display them in the form of an illuminated LED ring. We decided to identify occupied hours with a luminous section and free hours with extinguished light. The LED strip should be controlled by a Raspberry Pi and a 74AHCT125 line driver.


We decided to create a wall clock which is based on the classic design of a typical factory clock. With a simple design we wanted to set the focus on the function of the clock. The central surface of the clock consists of brushed aluminium, which is surrounded by an illuminated acrylic glass. We 



The first iterations of the code were based on the programming language Python. For these there are already several libraries to control the APA102 or to process iCalendar data.

In the further course of development it turned out that Node.js also has access to the GPIO pins. Due to previous knowledge and a large selection of software packages, we finally decided to use the hooloovoo and ical2parse packages.

The code loads all events from the iCalendar that take place in the next 12 hours in a given room. The start and end times will then be mapped from 0-60 and the areas will light up to indicate room occupancy. Furthermore, all LEDs pulsate when the air quality sensor value exceeds a critical value. The script is executed in a given interval via a cronjob.

Sensor technology

In the course of the project we iterated various possibilities to add further functions to the clock. Therefore we implemented an air quality sensor of the type "Grove - Air Quality Sensor v1.3". This sensor reacts to substances such as carbon monoxide, alcohol or formaldehyde in the air and outputs an analog value about the air quality. As soon as the sensor measures a reading above the set thresholds, the LED stripe pulsates red to alert people in the building.