Continuing the theme of examining metaphors for the measurement of, and perception of, time, the ROUND ABOUT Clock makes concrete the response to “What time is it?” … which may be… “it’s a round about eleven twenty five”.
A rotating face – the “round-about” – and a periphery of lights combine to replace the hands of a traditional analogue clock such that time is displayed both spatially and through continual movement. (I plan to design a new and larger top disc for the “round-about” to have the lights fully illuminate the numerals, but as a prototype, this is quite functional.)
A stepper motor drives the “round-about” such that the current hour is always uppermost (and separately illuminated), while the periphery is illuminated to display the current number of minutes. As the hour progresses, the “round-about” turns towards the next hour as more of the periphery of the “round-about” is lit. At the top of each hour, the “round-about” spins to “re-home”, and return to the new time – sort of echoing the idea behind the phrase “… this time around”.
The ROUND ABOUT Clock is built using an Arduino Nano, a real-time clock module (based on the DS3231 RTC chip) and a 4-wire stepper motor driver (DRV8825 / A4988) driving a NEMA-17 stepper motor. The motor’s pulley drives the “round-about” using a toothed belt, although appropriately sized elastic bands would do. A A3144 Hall-effect sensor mounted in the body of the clock, and a rare-earth magnet located in the underside of the “round-about”, create a switch that allows the stepper motor to ‘home’ to a known absolute position. A rotating coupling (seen in the centre of the image below) made from a 1/4″ stereo jack plug and socket carries power, ground and signal to a strip of 30 addressable LEDs, glued around the periphery of the “round-about”.
The Arduino Nano, RTC clock module, the stepper motor driver module and the 5V voltage regulator are connected together on a small circuit board. Connections to the stepper motor, LED strip (via the stereo jack) and the Hall-effect sensor are made using simple header pins and sockets. The unit is powered from a 9v DC 2A “wall-wart” power supply. The simple 7.5″ square box is made from birch plywood with a thin ply lid, while the round-about is made up of two stacked disks of plywood – the upper sized for the strip of 30 LEDs while the lower serves as the stepper motor pulley. The top disc is made from 1/8″ plastic and the numerals cut using my CNC machine.
As Rihanna states and asks rhetorically…
“Round and around and around and around we go
Oh now tell me, now tell me, now tell me now you know”
“Not really sure how to feel about it
Something in the way you move”
Clearly, unlike the songstress, now you know!