Neopixel sticks boneyard

[chrisjx]

OK, I know I've been a bad boy and I know I'm usually pretty lucky but I burned out 4 neopixel sticks today. Very bad boy! I've plugged sticks, rings, strips of all lengths into arduino micros, tinkets (3V,5V), wall sockets (just kidding), and never had a failure before.

So now I'm looking carefully at the best practices and I'll be adding the 1000uf cap and a resistor in line with the data signal. I hope that will make me a good boy.

The question I have is that the wire from data out pin of the arduino-micro is about 4" from the Data In of the stick. Does it really matter if I put that resistor at the stick end? The best practices says it won't be effective if I put it on the arduino-micro end.

Thanks for any advice,
Chris.

[adafruit_support_mike]

The resistor controls ringing in the wire.

Electrical signals have wave properties, and waves reflect from hard surfaces. More technically, some of the energy in a wave reflects any time the wave encounters a material that's harder to move through than the one it's currently in.

Electrically, 'hardness' is equivalent to resistance (or more generally, impedance). When a signal in a soft/low-impedance medium (like a wire) hits a high-impedance medium (a large resistor, or in this case, a mosfet), energy in the wave will reflect back the other way.

That can cause a range of problems, dead pixels being one option on the list. Putting a resistor between the wire and the NeoPixel reduces the sudden "milliohms to megohms" jump in impedance at that point. The resistor also converts some of the excess energy to heat.

Four inch wires shouldn't see too many problems with ringing, but resistors only cost a couple of cents. The cost/benefit analysis favors using one even for small benefits.

We're also asking people to try putting a 10k resistor between DI and GND at the NeoPixel end of the connection.

Any wire more than an inch long picks up induced current from mains wiring and other nearby radio emitters (flourescent lights are big offenders), and even a few nanoamps can cause uncomfortably large voltage spikes. I recently did a test where I was able to observe 7v 60Hz spikes in a 20M resistor and a foot of wire. Adding a 10k pull-down reduced the spikes to a few millivolts.

[chrisjx]

Thank you, Mike, for that excellent input.

I'll try the following:

• * 1000uf cap between Gnd and +5VDC
  * 300 Ohm resistor at the input of first DI
  * 10K resistor between DI and Gnd.

The challenge for me is that there are 2 chained neopixels going into a tight space around a slot in an enclosure creating a display kind of like the Knight Rider car. I don't know where I'm going to put the capacitor yet or where to bend the resistors; there's barely enough room for the ribbon cable.

If this is a permanent issue, I vote for adding those resistors to the stick in the next design... or maybe just some through holes for adding to the first stick? I think this would be important, especially if you've got folks like me who will fondle them, plug into active circuits, plug and unplug phone chargers as power sources, incorporate them into wearables, etc.

Thanks for your help,
Chris.

[westoutwest]

Total n00b here, sitting in front of:
- NeoPixel Stick - 8 x WS2812 5050 RGB LED with Integrated Drivers
- WS2812S 5050 RGB LED with Integrated Driver Chip - 10 Pack
- NeoPixel Mini PCB - Pack of 5
- Adafruit NeoPixel Digital RGB LED Weatherproof Strip 60 LED -1m

It's time to get started learning about this stuff. I've read through the Neo BP guide and have the resistor and capacitor mentioned and thought I'd get started with the low$$, $5 stick first in case I screw up. However, I'm confused by the mention of integrated drivers and the comment about 'no external choke resistors required' for the stick.

So I'm not sure what an integrated driver is and assume the no resistor means... no resistor is needed to choke/limit (current/voltage/whatever), but what about the capacitor?

Then I also make the assumption that this only applies to the stick, but I'm not certain. Don't really wanna fry any of these goodies, so I thought I'd ask for some clarification here. Based on the post that started this thread, I assume the precautions apply across the board. Still confused though as I watched the new product showcase with the stick and no mention was made of this - and it was plugged right into a breadboard.
Thanks!!

[chrisjx]

WestOutWest,

You should probably hook up the cap and the resistor as Mike recommends. I have to say, I've abused these sticks and the neopixel strands beyond what would be expected reasonable behavior. I've plugged them into active circuits (where the pattern picks up where it is in the sequence), I've reset the arduino micro, the trinket, and worn them as I cavorted around a campfire in the desert. Never had a problem. Until last week when I plugged into a 5V source from a tiny Via PC (http://www.viaembedded.com/en/products/ ... -P910.html). Blew out 5 of them.

The "integrated drivers" refers to a tiny integrated circuit (heretofore added to the circuit externally) which is now included inside the RGB LED package. Look closely and you can see a tiny black dot in the middle; I think that is the IC. It's called a driver, because it "drives" the LEDs for optimum performance. So it's different from software drivers we often use for usb devices and the like.

As I say, Mike's advice is probably the right thing to do, but you might want to just get it set up and see it work. Have some fun and see some color. Then worry about protecting it from environmental conditions.

Our short term fix is procedural; no plugging into active circuits because that's what we were doing each time they went dead.

Good luck,
Chris.

[westoutwest]

Thanks for the reply, Chris. After a bit of mucking around, I actually got it to work. I now see where the description for the stick has the blurb in there about the cap and the resistor, I missed it the first time around. I followed the attachment order precisely and will have to figure out how to deal with that impractical approach in the permanent installation.

Thanks again!
West

[chrisjx]

Well done. You're no longer a noob. ;)

[pburgess]

Never had a problem. Until last week when I plugged into a 5V source from a tiny Via PC [...] Blew out 5 of them.

Was this a first-pixel problem or did you toast the whole strip/strand? Have you measured the voltage from the supply? Did they die when power was switched on, or was it spontaneous in the midst of running?

Still trying to deduce the cause of the remaining first-pixel deaths, because I've yet to reproduce the effect here. Whatever power supply you're using with the Via board, maybe I need to track one down.

[chrisjx]

We were using the 5VDC from the Via that is intended to power floppy drives. As measured it looks like a solid 5V. It seems to have killed all the LEDs not just the first.

It was a classic case of one got blown, then we tried another while powered, then in disbelief we plugged in another; pop, pop, pop.

Haven't zapped one since, but we've stopped plugging them in to a powered up system.

I'd be willing to send the poor dead ones to you if you think that would help.