Cautionary tale of burning out pixel strips

EL Wire/Tape/Panels, LEDs, pixels and strips, LCDs and TFTs, etc products from Adafruit

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
tjwood
 
Posts: 22
Joined: Fri Nov 29, 2013 3:58 pm

Cautionary tale of burning out pixel strips

Post by tjwood »

By some measure, this is user error (or at least insufficient paranoia). But, it seems that the 144 LED NeoPixel strips are not very forgiving and the "uberguide" leaves out an important step.

On my first strip, I carefully followed the wiring guide on the first page of the uberguide http://learn.adafruit.com/adafruit-neop ... no-library and then loaded the sample code right below that on the page. When hooking up the power, all the pixels flashed brightly and nothing worked. It turns out on the NEXT page http://learn.adafruit.com/adafruit-neop ... uide/power there are some critical hints. In particular, while there was a built-in 300 Ohm resistor on the data-in (so the red you-will-fry-it boxes weren't an issue), there is no mention on the first wiring diagram that you need a capacitor to avoid power spikes. Obviously, I could have read all the instructions and avoided that, but putting the wiring diagram and sample code on the first page really makes it seem like the person following along should do those things in that order.

(Interestingly, the red box on the second page of the uberguide says 470 Ohm for the data-in resistor, but the one built-in on the 144 pixel strip measures at 300 for me…)

Hooking up a meter, I can see 5V between +/- all the way at the end of the strip, but checking between data and ground shows zero (even if I jumper data-in into the middle of the cable, with a 330 Ohm resistor).

So, for my next strip, I hooked up the capacitor and it worked fine. But, then tonight I was testing it installed in a cramped location and accidentally swapped signal and ground. The first strip lit up an ugly yellow before I could pull it and now nothing. I haven't tried bypassing the first pixel, so there might be something salvageable there or might not be. I don't know if it is practical to add any polarity protection in the strips, but as is they are fairly expensive and fragile.

If I opt to by any more of these, I'll want to protect myself from idiocy by always using JST SM connectors wherever possible instead of inserting jumper wires from the Arduino to the JST on the strip. Strangely, the strips I received have 3 pin JST SM connectors, but Adafruit only seems to sell 2 and 4, so I'll need to find some of those elsewhere.

User avatar
adafruit_support_bill
 
Posts: 88088
Joined: Sat Feb 07, 2009 10:11 am

Re: Cautionary tale of burning out pixel strips

Post by adafruit_support_bill »

Thanks for the feedback. I have replicated the warnings on the first page of the uberguide.
(Interestingly, the red box on the second page of the uberguide says 470 Ohm for the data-in resistor, but the one built-in on the 144 pixel strip measures at 300 for me…)
The exact value of this is not critical. It serves to damp out any ringing in the signal line. This can be a problem with longer signal runs.
Strangely, the strips I received have 3 pin JST SM connectors, but Adafruit only seems to sell 2 and 4, so I'll need to find some of those elsewhere.
We don't have a reliable source for the 3 pin connectors yet. But we find that it works fine using 3 out of 4 pins on the 4 pin connectors.

User avatar
tjwood
 
Posts: 22
Joined: Fri Nov 29, 2013 3:58 pm

Re: Cautionary tale of burning out pixel strips

Post by tjwood »

Nice improvement! One minor tweak, on http://learn.adafruit.com/adafruit-neop ... -practices, the note about the capacitor looks like a caption for the image instead of an item in the list. I suspect people will skip it in that position, but hopefully they'll see the red box on the next page. Still would be better to move that down into the list.

Thanks!

User avatar
pburgess
 
Posts: 4161
Joined: Sun Oct 26, 2008 2:29 am

Re: Cautionary tale of burning out pixel strips

Post by pburgess »

Thanks for the feedback. Page updated!

Locked
Please be positive and constructive with your questions and comments.

Return to “Glowy things (LCD, LED, TFT, EL) purchased at Adafruit”