Bluetooth capacitor - is it upsetting my accent LEDs?

Anyone seen this before (see video)?

Ignore the white inner LED, but the red and green LEDs are coded just to blink with the blade on, but they’re flickering.

I’ve installed a BT909 Bluetooth module with neg from LED pad 1 for auto-shutdown, along with the recommended capacitor (CAP CER 47UF 6.3V 0805) between 3.3 volt pad and Ground. Those LEDs are running positives from the same 3.3 volt pad that has the capacitor, so I’m guessing the capacitor is upsetting them somehow.

Unless anyone can suggest what else might be causing it? I’ve used the same config and essentially the same build lots of times in the past, but this is the first time I’ve fitted Bluetooth.

Looks like I’ll need to move them to hard off the battery positive. Resistors should be enough - 100 ohm red, 47 ohm green and they’re only runnng at about one third power in the config.

Just thought I’d ask here before re-routing things.
Thanks in advance.

I can’t think of a reason that BT or the capacitor would make your LEDs flicker, at least not like that.

It’s hard for me to ignore it, because it looks like the red and green are flickering when it is flickering, which makes me think that maybe there is a short between them somehow?

Hmmmm. As always you’re right Prof, but I don’t understand why.

I’ve just re-programmed so the inner white LED is just off (StylePtr< Black >).

The remaining blue inner LED is an smd LED added to the Bluetooth module as a status indicator.

Wiring setup is:

3mm LEDs:

Positives - combined to 3.3 volt pad.

Red Neg - LED Power pad 4

Green Neg - LED Power pad 5

Inner white pixel LED:

Positive to battery positive

Negative to LED Power Pad 6

Data 2 with 330 ohm resistor

And this time it works fine.

I’ve checked for shorts with a meter and there are none between any of the LED sides, except of course for the two 3mm LED positives which go to the 3.3 volt pad.

Very odd.

The white inner LED is set to blink with the blade colour with blade off, then strobe white/black with blade on. I’ve tried turning that white down in the config to Rgb<150,150,150> in case the draw at full white was too much, but the problem still comes back when I code it to use that inner pixel LED. :frowning:

Definitely something to do with that inner LED.

Tried a config where the first preset included both bluetooth and inner LED active - fault persisted.

Second preset switched off Bluetooth - fault persisted;

Third preset switched Bluetooth back on but switched off inner LED - fault fixed.

It can’t be a short if config changes fixes it I wouldn’t have thought, but I could be wrong, though my meter says there are no shorts.

The only other thing is the physical pixel LED itself. I got it off ebay. It’s a 5mm dome style but with an RGB pixel inner. Connections are positive, negative, data in, data out. Data out obviously not used. But I can’t vouch for the quality. Alarm bells did ring when the wiring diagram that came with it showed anode and cathode the wrong way around (I tried it and it didn’t work. Threw that one away and wired another one opposite way round which did work). But could a cheap and nasty pixel LED upset things like this?

I might try swapping it out for a normal pixel from a blade strip offcut as I know they are decent quality.

Other than that I’m kind of at a loss.

OK, I’ve figured it out!

The inner LED is closer to the red/green LEDs than I thought, and Prof, you are, as always, 100 percent right to spot them flickering in sync:
the red/green LEDs weren’t flickering at all - the white inner LED was shining THROUGH the red/green LEDs from underneath!


I’ll get my coat!

Thanks as always for taking the time Prof. It is appreciated!
Sorry for being such a numpty on this one. LOL!


That’s a first. Congrats Chris!