Doubt about the 85 columns

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Doubt about the 85 columns

Post by Pati » Sun Nov 14, 2010 7:53 am

Hi Brad, It's me again =)

About my question, my doubt is about the total number of columns, How do you know that are 85? 

I mean, if I put the circuit Maybe, I don't know, in a ceiling fan. I guess I'll have more than 85 columns, right? So, how I can determine the total number of columns? 

I made by myself a math formula to know that, but I don't know is it correct! It is with the radius of the circle formed...  

That's it! Thanks for the help! 


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Re: Doubt about the 85 columns

Post by brad » Sun Nov 14, 2010 12:48 pm

Hi Pati, thats a good question.

It is mostly just a bit of trial and error. One thing you can think about is that if one LED is 5mm and let's say that your fan outer diameter is 1metre then it stands to reason that you could have 200 columns. So this is good for a starting point.

You would set your code so that everytime it passed the sensor, it would flash 200 times (drawing your 200 columns) you would then just have a delay between flashes (in the order of microseconds or milliseconds) then put it on your fan, and try it! You will need to find a good mix between your fan speed and the delay between flashing each column.

Let's say you spun it up and the display complete's it's 200 flashes in half a circle - this means that your fan is either spinning to slow OR your delay between flashes is to fast.

If you were to speed up the fan then you will find that the image will now take up more than just half a circle - this is because the LED's are still flashing as fast as before but now the motor is rotating faster.

One thing that you will need to think about is that the LED's in the center of the fan will not move as far as the ones on the outside.

I was working with a guy a couple of years ago trying to develop a colour display for helicopters. He has come up with some great stuff and the software may very well help you out also.

check it out here: ... index.html

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