Hi all, I'm hoping to get some help with some flashing issues on my

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Hi all, I’m hoping to get some help with some flashing issues on my 5x5x5 LED cube I’ve been working on. I’m using a NodeMCU esp8266, and for LEDs I am using 125 PL9823s (Supposedly similar to Neopixels? You’ll have to forgive me, I’m fairly new to this). Power is supplied to both the LEDs and the esp8266 by a 5V 60W power supply, and the data signal is being converted from 3.3V to 5V by this thing: https://www.jaycar.com.au/medias/sys_master/images/9071426961438/XC4486-dataSheetMain.pdf (that’s the best datasheet I could find, I know its not great).

The issue I’m getting is, whenever I try to display something even slightly complex, the entire cube will flash brightly every second or so, often multiple times per second. It seems (although I’m not certain) that each LED flashes whatever color it’s meant to be, but at full brightness.

In terms of versions, I’m running version 1.8.5 of the Arduino IDE on Linux, FastLED 3.1.6, and version 2.4.1 of the esp8266 plugin. I’m building for “NodeMCU 1.0 (ESP-12E Module)”.

Here’s a minimal example that I get issues with (see video):
https://gist.github.com/Christopherbikie/847d3b10455dc0202a1e266b49d24c19
The flashes become less frequent when DELAY_INTERVAL is increased.

I have tried adding both of
#define FASTLED_INTERRUPT_RETRY_COUNT 0
#define FASTLED_ALLOW_INTERRUPTS 0
before including FastLED (https://github.com/FastLED/FastLED/issues/367) to no affect.

Interestingly, if I plug in a USB cable into the esp8266 (disconnected at the other end), the flashing becomes significantly less frequent, maybe on average every 5 seconds. The USB cable has a ferrite bead - what that does is beyond my knowledge. Connecting the esp8266’s/LEDs’ ground to power supply casing seems to have the same affect, but I also tried two shorter USB cables without the ferrite bead - this did make any difference.

I should also note that I don’t have the 1000 μF across vcc and ground, mainly because I don’t have one lying around. I don’t think this is the cause, but correct me if I’m wrong.

So, any ideas on the cause of the flashing?

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I think that level converter may be your problem. It looks like a simple transistor device and maybe too slow for the speed of the data.

Try bypassing it completely… The 3.3V logic mat work. Many here do not use level converters but results do vary…

If you can adjust your 5V PSU, adjust it to 4.5 V, that could help if you have flaky results with the 3.3V data signal.

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I agree with @JP_Roy , it’s almost certainly the level shifter. You need to use a sn74hct245n.

See this research…
http://happyinmotion.com/?p=1247

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I also believe that these leds prefer 5.1 v

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@Christopher_Hall , nice cube :slight_smile:
I’ve been thinking about making one with the same leds…

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@JP_Roy First of all, thanks so much for your help! This seems to of helped considerably, but there’s still a bit of oddness going on.

I turned down the power supply voltage to around 4.7 V, as low as it goes. Previously I had it up at 5.5 V, copying this video https://youtu.be/R-arZ31-zJo?t=6m24s, which my cube is heavily based on. I then shorted the esp8266 output to the first LED’s input by holding a jumper lead, and all was well, the cube worked perfectly!

However, upon soldering that connection, the cube was flashing again! Even more confusing, attaching a single end of a jumper lead to either the esp8266 output or the led input makes the cube work fine! I suppose I could just permanently attach a jumper lead, but I’d really like to know what causes this.

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@Christopher_Hall Difficult to be 100%, I was lucky with my guess of the level converter being the problem though that was an educated guess… :wink:

I would venture yet another lucky guess and suggest that you first double check all your soldering for cold solder joints !!

Next would be to follow Jeremy’s suggestion and add a much better level converter like the sn74hct245n, then you can go back to applying the full 5Vdc.

I do not know about the 5.5 Vdc recommendation from GreatScott ! I have seen a number of videos from that guy and he is very very accurate with his suggestions and conclusions but here I have some doubts.

Note that I have built my own cube a few years ago around these 8mm RGB LEDs with integrated WS2811 chips so I am talking from experience here…

https://plus.google.com/106626345342202981932/posts/RCnWduhk9Sr

https://plus.google.com/106626345342202981932/posts/6cTydVvqdGj

and finally a short, accelerated build video of that cube…

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@Christopher_Hall if when you touch something the flashes disappear it’s problably due to ground issues. The wires tend to grab noise around the room and then disturb the signal. As surggested using a 74hc245 should help you as the signal will be stronger. I had the same issue on my last build. Just by standing next to the signal wire I could eliminate flashes.
Great build by the way !!

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@JP_Roy @Yves_BAZIN Thanks again for the help! I will look into getting a 74hc245. In the meantime, I’ve bodged a connection from the circuit’s ground to the power supply’s casing, which seems to work for now. The cube’s looking fantastic! I’ll be sure to post when I’ve got it doing something pretty. If it’s okay I might see if I can get JP/Peter’s atom thing working, but we’ll have to see how it works on a 5x5x5.