The Stack Archive

Swiss robot clock writes time on a whiteboard

Fri 20 Feb 2015


Perhaps not the most stylish or practical clock to ever grace a wall, but nevertheless it’s Swiss and it’s cool – the Whiteboard Clock is a little time-keeping device designed by Maurice Bos which actually jots the current time onto a whiteboard with a dry wipe marker pen.

The robot clock uses 3D-printed arms to hold the pen in place, while magnets help it keep its place against the whiteboard.

The clock mechanism, a tiny PIC16F1454 microcontroller, currently operates the marker to write the time every five minutes. A 433MHz receiver is used to wirelessly transmit information and updates as pulses from Bos’ computer: ones are transmitted as a 0.20ms signal followed by a 0.10ms silence, and zeros as the reverse.

“All messages are sent multiple times, so if a message is received with some error […] it is simply discarded,” says Bos. “The message index is incremented every time the transmitter transmits a new message. The receiver uses this byte to detect whether a message is just one of the retransmissions of a previously received message, or if it is a new one.”

The font is also sent in a similarly geeky fashion in series of x and y coordinates. When new time information is sent to the device, a C++ programme is able to convert the pulses into dots and dashes which are then plotted by the marker pen.

A cronjob runs on Bos’ computer to push a time update to the microcontroller at specified intervals. When the information has been received a set of servo motors coordinate the arms to pick up the sponge and erase the previously recorded time. The pen is then taken out of its ‘dock’ and scrawls the time before returning to its station to avoid drying out.

Fancy one for the office? Find out how to make your own here.


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