60 pixel/meter strip behaving irregularly (230 leds total)

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Cerbrus
 
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60 pixel/meter strip behaving irregularly (230 leds total)

Post by Cerbrus »

For a project at school, my team has to make a new interactive / multi-media "anything" for use in a skatepark.
The product we came up with is a grind box, with sensors that detect where a skater is, and a ledstrip on top, and in the front side of it, that reflect the skater's position:
Image
(I'm afraid that's the best pic I have of when it worked)

We tested the product at a skate park recently, it worked just fine.

However, the next day the strip wouldn't light up, turns out the first leds on both sections of the strip were burned out.
We replaced those two leds, added a capacitor (1000 µF, 6.3V) to the power supply, and made sure the ground connected to the arduino (Due).
We also have a power switch on the 5V line, which we turn off before the system is shut down, and turn on only after the system's started, to make sure it's always the ground that's connected before 5V.
The power supply (5V & gnd) is connected close to the middle of the strip (after led 117).

Now, the strip is behaving irregularly.
There's a video showing what's happening, here:
http://www.youtube.com/watch?v=mTnSGJRwtvY

I'm running the strandtest code on it, with only the pin address changed to 2, and the led count to 230.
When the arduino is started, the strip works fine for a moment, most of the times, then starts flickering once or twice. During the "rainbow" phase of the strandtest, the strip switches between flipping out and just showing the rainbow.

The wiring to the strip isn't interrupted anywhere, and since the strip does work every now and then, I'm pretty certain the data connection is solid

Now, what my question would be, is what could be wrong?
I really don't want to snip off another led under the assumption it's broken

P.S: I'm happy to provide more photos or details of connections and other parts, if necessary.

Edit: I've currently stripped everything from the arduino that was not related to the led strip, and it seems there might have been an issue there.
It's only flickering a little bit on the 4th quarter of the strip (Power is connected at the start and in the middle, so that might be the issue).

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pburgess
 
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Re: 60 pixel/meter strip behaving irregularly (230 leds tota

Post by pburgess »

Do you have a 5V Arduino (Uno or whatnot) you could test this with? Flickering and erratic behavior is often a symptom when trying to control the LEDs from a 3.3V device...but maybe not, so testing from a 5V Arduino would be helpful.

Cerbrus
 
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Re: 60 pixel/meter strip behaving irregularly (230 leds tota

Post by Cerbrus »

We're using a Due, so that should be able to supply 5V. However, the strip is connected to a external power supply linked to in the OP.

Cerbrus
 
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Re: 60 pixel/meter strip behaving irregularly (230 leds tota

Post by Cerbrus »

Turns out the first 2 leds were burnt out again.
We're adding capacitors to the power supply wires, as close to the ends of the strip as possible, instead of at the power supply itself. (a 6.3v 1000µF one, and a 100µF one in parallel)

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pburgess
 
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Re: 60 pixel/meter strip behaving irregularly (230 leds tota

Post by pburgess »

Regarding 5V vs 3.3V: referring to logic levels here, not the power supply. The Due has 3.3V logic, which is right at the threshold of what 5V-powered NeoPixels will recognize. When riding this thin edge, tiny variances in voltage (which can be influenced by factors such as temperature) can make the difference between "working" and "not working."

Regarding the burned-out pixels: try adding a 470 Ohm (or thereabouts) resistor between the data pin on the Arduino and the strip input, see if this prevents future burnouts. Also, about how long is the wire between the two?

Cerbrus
 
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Joined: Tue Jan 07, 2014 5:30 am

Re: 60 pixel/meter strip behaving irregularly (230 leds tota

Post by Cerbrus »

pburgess wrote:Regarding 5V vs 3.3V: referring to logic levels here, not the power supply. The Due has 3.3V logic, which is right at the threshold of what 5V-powered NeoPixels will recognize. When riding this thin edge, tiny variances in voltage (which can be influenced by factors such as temperature) can make the difference between "working" and "not working."

Regarding the burned-out pixels: try adding a 470 Ohm (or thereabouts) resistor between the data pin on the Arduino and the strip input, see if this prevents future burnouts. Also, about how long is the wire between the two?
Ah, that's worth a try, then. We should have another arduino laying around somewhere...
We'll also add the resistor.

The stip is split in 2 parts of roughly 2 meters. The data pin is connected to the input on strip 1 with about 10cm of wire, straight from the arduino. The output of strip one's data is connected to strip 2 with about 30cm of wire.
The + and ground are connected on both sides of both strips to the power supply that's positioned in the middle:
Image
The blue dots are the 6.3v 1000µF and a100µF capacitors in parallel:
Image(With some heat shrink tubing around the bare wires)

Cerbrus
 
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Re: 60 pixel/meter strip behaving irregularly (230 leds tota

Post by Cerbrus »

A little update:

Last week, we had the strips connected to two Uno's, with a shared power supply, and connected to our due for serial communication (I2C / Wire library), so the Due can still control the strip according to it's sensor input. This didn't work, and one of the leds burnt out again (If only I knew why...)

Since the project's deadline is approaching, we compromised by removing everything but the bare essentials necessary to get the strip working. Now, there's 1 uno and the power supply, to which the two strips are connected in parallel. I've added a small button to trigger a "demo" (a colorWipe).
When the demo isn't running, it's just showing off with the strandtest code.
So far, the strip hasn't burnt out again.

It's a shame the strip doesn't accurately reflect the skater's position with the demo code, but it's better than no light at all.
There's still the "wow" effect from having 60 leds per meter light up the thing in a fancy rainbow ;-)

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