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How to wire three joining programmeable LED strips?
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How to wire three joining programmeable LED strips?

by jesteringo on Sun Feb 17, 2019 9:47 am

Hi, I'm working on this project featuring a cube where I want to light every edge on the inside. A power source/arduino will outside, leading into a corner of the cube with wires, where it will light a programmeable WS2812B type LED strip. I do not know circuitry well and it seem that the only way to fully light each edge will be to use this (see image) method, of first leading the led strip around the bottom four edges, then up one edge, and then again around the top four edges. This leaves the 3 red marked edges with no led strip. So it seems I would have to join 3 short led strips to the main LED strip. Would this wiring work? And if so, would it still work if the short vertical LED strip was joined to either the left or right upper led strip in my sketch? Or I may have it completely wrong, I'm unsure how this should work. My sketch feels wrong but I know that these strips work in strange ways. I've also included a slight closeup of how the LED strips look. Would the 3 red LED strips work just wired at the top only? Instead of wired at the bottom too?


for.jpg
for.jpg (68.29 KiB) Viewed 96 times



strip looks.jpg
strip looks.jpg (40.92 KiB) Viewed 96 times

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Re: How to wire three joining programmeable LED strips?

by adafruit_support_bill on Sun Feb 17, 2019 1:13 pm

You could wire them that way. Where the strips 'fan out' like that, the pixels on both branches will have the same effective addresses and will display the same pattern.

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Re: How to wire three joining programmeable LED strips?

by jesteringo on Sun Feb 17, 2019 2:25 pm

Hi adafruit_support_bill, ok thank you very much that helps!

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Re: How to wire three joining programmeable LED strips?

by adafruit_support_bill on Sun Feb 17, 2019 3:18 pm

One other detail. You didn't specify how large the cube is. But if you have more than a few hundred pixels in total, you may want to consider feeding power from multiple corners of the cube.

A good rule of thumb is for no pixel to be more than about 200 pixels distant from a power feed. This is to minimize the voltage drop along the length of a strip. If a pixel is too far from the power feed, the voltage drop can cause a color shift and/or unstable operation.

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Re: How to wire three joining programmeable LED strips?

by jesteringo on Mon Feb 18, 2019 1:12 pm

Hi Bill,

Its a 25 x 25 x 25cm cube - thank you for that advice. I did see that the USB power alone struggles to light my entire strip (though I did buy a longer strip than that I will need for this project), but I have a power adapter that seems to light it all properly, though I have had an issue where from a certain point it often doesn't light up to the end of the strip - but when I physically jiggle/manipulate the strip the rest does light up, but that last portion does not do the animation that I have coded into the arduino, it just lights up but the lighting doesn't change, so I've wondered if this is due to lack of sufficient power or due to a physical fault in the strip.

Thanks again

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Re: How to wire three joining programmeable LED strips?

by adafruit_support_bill on Mon Feb 18, 2019 1:44 pm

RGB pixels can draw as much as 60mA each at full intensity white. At that rate, 10 pixels would be enough to overload a typical USB port.
Most applications on average run the pixels at lower intensity, so 1/3 to 1/2 of that 'worst-case' estimate is often sufficient.

If there is a voltage drop issue toward the end of the strip, pixels closer to the end will tend to show a color-shift toward the red end of the spectrum. If the colors all look fine, it is possible that you have an intermittent solder joint somewhere in the strip.

This can be a result of a sharp bend or repeated flexing of the strip which can crack a solder joint. If you can locate the broken joint (the pixel where the misbehavior starts - or the oe just before it) you can typically fix it by just re-flowing the solder joints with the tip of your soldering iron.

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