Having Trouble with Multiple NeoPixel Matrices. Old LEDs worked fine, new ones not so much

Other Hardware LEDs and Multiplexing
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Hi,

I'm having an issue with a NeoPixel project and hoping someone might be able to point me in the right direction.

Details:
-I'm running 4 matrices of NeoPixels from an Arduino Nano 33 BLE Sense.
-LEDs are WS2812B, GRB color order and I have Bitstream set to 800 KHZ.
-Two matrices are 11x11, one is 7x3 and the last is 17x3.
-Each matrix has it's own DIN output from the Nano and they're all running through a level converter to step up the 3.3v to 5v.
-Each LED matrix has it's own 5v power supply from different batteries.

Description of problem:
-All 4 matrices were running fine until I replaced one of them with new NeoPixels (the 17x3 was previously 17x1).
-The previous 3 matrices are still good, but the new one is not working (nothing lights up or it glitches or it runs through one loop and then stops while the other matrices keep going).
-If I plug in the old 17x1 strip it works fine.
-The new LEDs work perfectly well when I run an LED strand test through an Arduino Uno so it's not the LEDs or any connections as far as I can see.

The only thing I can think of is that there is something different about the new NeoPixels but they are the same product from the same manufacturer with the same specs. I'm baffled!

Let me know if you can shed any light on this.

Cheers,
Neal

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So that "level converter" is using a 74HCT14 or other 74HCT or 74AHC chip?

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When you plug in the old 17x1 strip, are you still running the code for the 17x3 matrix, or are you changing the code?

4

Documentation does not have any of those chip numbers. Schematic and Datasheet say BSS138 - N-Channel Logic Level Enhancement Mode Field Effect Transistor.

Here's link to product, datasheet and schematic

5

Running same code for 17x3 matrix when checking both. Unplugging one and plugging in other while program is running.

6

Thought as much. :roll_eyes:

That device is totally unsuitable for controlling NeoPixels so while it sort of works in your situation, it may well be the reason for the different NeoPixels failing if they are not as tolerant of the distortion the "bidirectional level converter" is introducing.

I strongly suggest you get a 74HCT14 (note the "T") and use three pairs of inverters, each wired in tandem so as to invert the signal twice, as your three "level converters". That chip will do the job nicely and should be very readily available.

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Ok, great! I'm going to investigate this further and report back with how it goes.

Thanks so much for the guidance Paul

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74HCT1G126GV for 1 matrix or 74HCT126D for 4 matrices. The not used input on GND. The OE (output enable) pins on 5V. The not used can be on GND.

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Thanks for the advice guys.

I ended up ditching the level converter and wiring the 3.3v data outs from the Nano directly to the NeoPixels. Still powering the LEDs with 5v. Works perfectly.

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Luck.

You may continue to be lucky, in which case, no problem. But if you make some apparently trivial change to the circuit later, and it then stops working reliably, take another look at the advice from @Paul_B above.

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Will keep that in mind, thanks.

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