Did not know where else to ask about this, so if it is off-topic I would gladly take some pointers as to where the correct place would be. I would like to make one of those spinning LED fans that can project an image that looks like a hologram. I am not looking for anything with big resolution, just want to try it out, see if it is possible.
So I have a couple of questions:
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Is 30 Hz frequency for the fan enough to be able to see images without lag? I'm basing this off of the fact that 30 fps is needed for a video to be smooth for a human, so if a fan is spinning 30 times in a second, that means a human won't be able to see it?
If this is correct, would a 6VDC 340mA motor which can spin at 14400rpm (thats 240 Hz) be enough? -
What LED density should the LED matrix on the fan be in order for the images be recognizable? Or is a LED strip a better idea?
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I'm thinking that the controls should go to an Arduino. Is that at least possible? I think I should be able to divide a circle into 30 parts and control which LED's should be on in each section of a revolution.
EDIT:
Let's say I want to control an 4×8 RGB LED matrix (something like this https://www.adafruit.com/product/2945). I want to plot simple pictures like an arrow or a drawn cat face. While searching I thought the MAX72XX ICs would work for this?
The picture I think would be sent via USB (or something similar because MAX72XX support SPI) form the computer, one at a time.
Best Answer
Here is a picture of a simple toy clock that runs off a USB port.
The picture was taken at 1/40 sec, I didn't quite get one revolution. So about 1/30 would be one revolution.
The LEDs are on only one blade. The minimum arc that I see is about 2.8 degrees, so the LEDs are updated about 128 times per revolution (360/2.8).
Therefore, the LEDs are updated about 3840 times per second (30 * 128).
Now this is just a small toy. Something larger will need to update at a smaller angle. You will need to do some geometry calculations to get an update rate for a whatever "pixel" size you choose.
Realize that making something close to photo-realistic from scratch is a massive job.