Anomalous behaviour of LED strips with Plasma2040

I created an LED strip light with 72 addressable LEDs, driven from a Plasma2040, which slowly varies its colour throughout the day to simulate the daylight conditions in Tokyo. I had occasion to change the LED strip recently using another strip which I purchased from Pimoroni some time ago and which I had laying around doing nothing. When I fired up the light, the strip behaves differently in that the LEDs are not all the same colour as intended and experienced previously but now seem to progress in an “RGB” sequence along the strip. I notice that the replacement LEDs appear slightly different and I think have a separate white LED in each. Have I simply got the wrong type of LED strip or is it likely to be some error in my coding which didn’t show up before? Thanks for any help you can offer.

If they have a separate White LED they need to be coded differently.
Getting Started with Plasma 2040 (


If your LEDs are in (surprise) disco mode or if fewer of them are lighting up than expected, you may have RGBW LEDs. Peer closely at the LED strip - if one half of each LED is yellow, then they have an extra white element, lucky you. Try initialising your led_strip object like this:

led_strip = plasma.WS2812(NUM_LEDS, 0, 0, plasma2040.DAT, rgbw=True)
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Thank you, alphanumeric, problem solved !

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Your welcome, I figured that would point you in the right direction.
I’m having a lot of fun with some Plasma Sticks. I have one Plasma Stick and 144 RGB LED strip setup as my desktop lighting. I use the Pimoroni Rotary Encoder Switch for the controller. I also have 2 Plasma Sticks setup on two mini artificial Christmas Trees to light the trees up in patterns. The more LED’s the better, lol. =)

I am quite impressed by both the LED strips and the Plasma2040 controller. I think I have found out what the problem was with my original set up; one of the LEDs about a third of the way down the chain must have come loose. If I apply gentle pressure to it, everything works. The trouble is I think they may be BGA-type devices with the solder connection underneath the body and these are notoriously difficult to repair. Sometimes a judicious application of heat can cure it but you run the risk of damaging the whole strip. Probably better to simply cut the defective LED out. Haven’t tried this personally but since you can daisy chain them I don’t see why it’s not possible. Here is an image of the whole lamp in case you are interested. The idea is that the light changes very slowly throughout the day to match the location of the light. My next job, when I get around to it, is to include a world time facility to automatically adjust to any chosen location. Thanks again for the original steer.

Cutting the one LED out should work, like you said, daisy chain it back together. Just remember to change your number of LED’s in your code.

I got a Unicorn Hat HD that had one dud LED. It wouldn’t light up Red. Pimoroni sent me a replacement and I put it aside. I just recently got a hot air reflow and gave that a try on that dud led. Now its working. It took me a couple of attempts, increasing the temp a bit on each try. It’s a lot easier on a circuit board, I was only worried about melting the LED, lol.

You could try putting your soldering iron on the back side of the strip. while holding the LED down. The heat transfer might be enough. Your going to cut it out anyway if it doesn’t work. It should only damage the strip under that LED if it melts something.

Thanks Alphanumeric. I don’t think I mentioned in my previous post that I had a “spare” LED strip so the pressure is off. I had thought of the heat approach but other than a soldering iron I only have a hot air gun and I thought that might be a bit like " a sledgehammer to crack a walnut". I am sure I will find a way to sort the original strip out as they are too good to waste !