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RobG

RGB Globe

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Or a white hula hoop with discreet LED's installed on the inner side, projecting on the outer side.

The hula hoop diffusing the light of the individual LEDs would look awesome, but i'm quite sure that it isn't stiff enough to support the weight of the electronics at high rpm. it would propably bend to the form of an egg at 3600rpm. I didn't even think about the rpm needed to achieve a persistent image. You definetly don't want to spin a hula hoop or a alloy bicycle rim at a couple hundred rpm :D

Even if you could handle the vibrations you would have to put this thing in a display box or a cage to prevent somebody or something putting their fingers in it ;)

Unfortunately, LED strip is not going to work, it's too slow. It takes ~60us to update each LED (~30us in fast mode, but I believe those strips are configured to use slow speed,) so to update 180 LEDs you would need 10.8ms.

 

For comparison, TLC59281 has 35MHz data transfer rate, which means you can update (in theory and @16MHz) 180 LEDs in just 270us, so @3600rpm, you can get 60 vertical lines per rotation (120 lines if the strip is all around.)

Yeah, i didn't take care of the math behind your project when throwing in the idea with the spinning bicycle rim... Although it is not really achievable with LED strips and a globe of this size spinning at 3600rpm, it would be so damn cool ;)

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The hula hoop diffusing the light of the individual LEDs would look awesome, but i'm quite sure that it isn't stiff enough to support the weight of the electronics at high rpm. it would propably bend to the form of an egg at 3600rpm. I didn't even think about the rpm needed to achieve a persistent image. You definetly don't want to spin a hula hoop or a alloy bicycle rim at a couple hundred rpm :grin:

Even if you could handle the vibrations you would have to put this thing in a display box or a cage to prevent somebody or something putting their fingers in it ;-)

The hoop could be made to withstand ovalling by using an acrylic rod spanning vertically. But, yeah it would have to be spinning quite the speed

 

Less ambitious maybe... a frisbee or frosted acrylic sphere?

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The half circle:

9 x TLC59281DBQ

9 x 0.1uF 0805

9 x 2.2k (or higher) 0805

 

The controller:

TBD but in my proto globe, I'll be using my F5132 board which is basically F5132 with few external parts.

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The half circle:

9 x TLC59281DBQ

9 x 0.1uF 0805

9 x 2.2k (or higher) 0805

 

The controller:

TBD but in my proto globe, I'll be using my F5132 board which is basically F5132 with few external parts.

Ouch- just realized how much the parts are. I'll hold off for now- spent all my Christmas money already :)

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TLC59281DBQ - $0.81 @ Avnet

LEDs - $0.27 @ Tayda or $16/100pcs @ Ali

3 PCBs - $7.5

 

Controller should be around $5-$8

Cheapest shipping @ Avnet is $8 though.  Mouser has them at 0.87 with $5 shipping.  Better overall price.  I might put in an order - I've been meaning to pick up a few things @ Mouser anyway.

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