Updated Control Board

A project log for Volumetric POV Display

A 3D rotational persistence of vision display

Jamal-Ra-DavisJamal-Ra-Davis 07/02/2019 at 20:013 Comments

The main control board was updated with the following hardware:

The boards were fabricated using OSH park, and I had a stencil made through OSH Stencils. This was my first time using a stencil but aside from some minor solder bridges between the microcontroller pins, everything came out fine, and I found the experience to be much easier than placing the solder paste on each pad by hand. 

I feel it's worth noting that I incorporate the receiving circuitry for the inductive coils onto the control board itself, instead of just mounting the coil's PCB. This involves desoldering the components from the coil's PCB and resoldering them onto my board. Which is definitely a less than ideal situation.  I would love to instead develop my own inductive power transmission circuit as to not have to rely on these modules, but my previous attempts didn't pan out. If anyone has any comments or advice on this matter, I'd very much appreciate it.


Stefan Krüger wrote 07/03/2019 at 07:18 point

Why did you create a 'optocouple' for the trigger signal?
you could just use one phototransistors and a static-on ir-led on the rotating disc?!
or iam missing some point?! ;-)

Regarding the Power-transmission -
i have written down all my research things at

the 'easiest' circuit i found was the Application Note 'High Power Wireless Power Transfer for the Industrial Environment' from Würth Elektronik
but i did not test any of them yet..

Main Problem with the 'High-Efficiency' concepts is that the coils are bound to a ferrite base  - and so have no hole for shafts in the center :-(
and multiple people told me that its about no way to drill or cut ferrite without it cracking and falling into peaces...

so if i get back to my project someday i will first try with some self-made slip-rings for power...
should be much easier and with a relative big bank of capacitors and a dc-dc converter on the rotating disc all noise should be gone.. so i can use 'high voltage' (= my raw battery voltage ~12V) on the rings and then convert it down to the 5V for the leds and 3.3V for the controller..

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Jamal-Ra-Davis wrote 07/03/2019 at 20:24 point

Hahaha, there is a little bit more to my reasoning behind doing it the way I did.

I've been trying to debug the root cause of the screen jitter I've been seeing on the display, and one of my theories was that the hall effect trigger signal might have a little bit of noise or not be triggering in exactly the same spot each time. Though, on the previous version of the control board, I didn't have a way to observe the hall effect trigger signal while it was spinning. Doing it this way lets me look at pretty much a 1-to-1 version of the trigger signal, and I can also use it for the motor speed control.

But yeah, if I was only trying to generate a signal to use for speed control, the method you suggested would be much simpler. :)

And thank you for the links to those resources, I'll definitely take a look at them.

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Stefan Krüger wrote 07/04/2019 at 08:09 point

thanks for explaining!! :-)
your reasoning is really good ;-)
to debug this POV things it hard - you can't probe with a scope at a fast rotating disc ;-) ;-)

something i also should keep in mind..... ;-)

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