# Control of 28 stepper motors // Rhei Clock by Damjan Stankovic

Hello all!

I am trying to understand how Damjan Stankovic’s Rhei Clock works.

As of what i can see, he uses stepper motors to control the clock, 7 for each digit = 28 total.
How is he managing this much stepper motors?

If i were asked how one should manage this many motors i would say something like, buy 28 drivers - one for each motor - then divide them by four into collections each consisting of seven drivers. These collections of seven drivers could then each be controlled by Atmega328’s. Then the four Atmegas could be controlled with one master Atmega - or something in that direction.

Can anybody shed some light upon this magnificent clock?

Best regards.

Grumpy_Mike:

Sorry, updated.

I can't figure out what is going on in the video. I can't see even one stepper motor, never mind 28.

...R

This link http://www.hellorhei.com/ shown at the end of the video you linked to shows you a lot more about how the clock works. Magnets are moved forwards to create a seven segment figure using ferromagnetic fluid.

Considering it took about a year for him to make I consider controlling that many stepping motors is the least of your problems. The mechanics look like a high precision job, and ferromagnetic fluids are made from quite nasty chemicals.

But yes just have 28 stepping motor drivers, you can probably switch the control signals with digital multiplexer chips.

I wonder could you get the same effect by energizing electromagnets - no moving parts?

...R

Robin2:
I wonder could you get the same effect by energizing electromagnets - no moving parts?

Possibly but the hysteresis will leave a permanent magnetic level even when the power is off.

The remanent field allows to toggle a segment on and off and keep it in the last state. A 180° flip can switch between both sides of the segment, with different colors, or 90° for face and side view.

A 180° flip can switch between both sides of the segment, with different colors,

Different colors of ferromagnetic fluid? Have you a link to that?

I meant mechanical segments.