Strange NeoPixel Behavior

[digital11]

So I have a 60 pixel NeoPixel strip that I've wired up to a Teensy 3.0 that is behaving strangely and I have no idea what's going on. The circuit is set up as such:
5V 10A power supply connected to LED strip and Teensy on their respective VIN & grounds. Signal input on LED is connected to a 100 ohm resistor, then to pin 2 of the Teensy. I loaded up AdaFruits strandtest and loaded it on to the Teensy and nothing happened. I hooked up my DSO Nano v3 Oscilloscope just to see if there was any signal being generated by the Teensy, then it magically started working. Whenever I unhook the scope, the LEDs freak out until I hook it back up again. What could be causing this?

[digital11]

I discovered that my multimeter causes it to work sometimes as well when I read voltage on the signal and ground lines

[EternalCore]

Add a 6-25v @ 1000uf capacitor to the positive and negative of the power going to the neopixel strand like they show in this picture below.

[digital11]

No dice

[EternalCore]

Why do you have a resistor on the data line of the neopixels?
Remove it and connect the neopixel data-in line directly to the data-out of the trinket then try the strip.
Also remove the power to the trinket while using the USB to power the trinket as it's conflicting with your power supply.

[digital11]

This is a Teensy, not a trinket. The resistor is there because I plan to use octows28011, and they recommend having a 47-200 resistor in line to reduce ringing and cross talk on the signal. Also, I have cut the usb VIN on the Teensy so it is no longer powered by usb, only by external power.

Also, I have tried it without the resistor with no effect.

[EternalCore]

Can you take a macro pic of the 1st couple of pixels on the strip?
The neopixels use PWM and Using a resistor on the data-out(PWM) line for the neopixel strip will make the neopixels not work, read more on PWM(Pulse-width modulation) here: http://en.wikipedia.org/wiki/Pulse-width_modulation

[digital11]

This is why im using a resistor: http://www.pjrc.com/teensy/td_libs_OctoWS2811.html
Will take a macro when I can. As I said though, removing the resistor made no difference, and doesn't explain why hooking up a multimeter or scope magically makes it start working.

[pburgess]

If the strip is being powered from 5V, then 3.3V (the Teensy 3.0 operating voltage) is right at the threshold of what the NeoPixels will register. Try using a slightly lower voltage for the pixels (e.g. 4.5V from three AA cells, 3.7V from LiPo), or a logic level converter (3.3V->5V) on the output of the Teensy.

[digital11]

Update: Still having issues. I am able to get it to work occasionally with the 1kuf cap at the power supply and no resistor on the signal, but only if i plug the power barrel in very slowly. If i do it too quickly the strip freezes with only some of the pixels lit. If I do it slow and gently enough, the animations start running. However, if I update the firmware and reboot the Teensy, it stops working until I gently re-insert the power barrel again.

Any ideas on how I could get this thing working reliably? I'm so stumped.

[EternalCore]

Do you have an Arduino you can test the strip with? If not then I recommend getting the Arduino UNO(R3) then test to see if the strip works.

[digital11]

I don't, but the strip (and the other dozen that I have) works perfectly on the teensy when on a breadboard. It's only when I hook it up directly that I run into problems.

[EternalCore]

I don't, but the strip (and the other dozen that I have) works perfectly on the teensy when on a breadboard. It's only when I hook it up directly that I run into problems.

Did you read this:

If the strip is being powered from 5V, then 3.3V (the Teensy 3.0 operating voltage) is right at the threshold of what the NeoPixels will register. Try using a slightly lower voltage for the pixels (e.g. 4.5V from three AA cells, 3.7V from LiPo), or a logic level converter (3.3V->5V) on the output of the Teensy.

So basically you can't use the Teensy 3.0 to power the strip because the Teensy 3.0 uses 3.3v and the neopixel strip requires 5v. Also use this tutorial to check your soldering: http://learn.adafruit.com/adafruit-guid ... n-problems

[digital11]

I have some logic level converters on the way, but I'm going to be out of town when they get here and really needed to have a working prototype up for my coworker to start animating.

The thing I'm not getting, is why it works sometimes when I slowly plug in the power supply. If I just knew what was behind that and could reproduce that in a circuit I'd be golden.

[EternalCore]

Also just to note that the project you want to do uses the strips with "WS2811 IC & LEDs", which was the Neopixels Version 1.0 strips and the Neopixel strips that Adafruit is carrying now has the "WS2812 LEDs" which is the Neopixels Version 2.0 strips. There are big differences between the two led strips so here are the data-sheets for them: WS2811 data-sheet & WS2812 data-sheet
This is most-likely why you're having such an issue getting it to work.