Hi guys I have some ws2812b that I am trying to connect to a skr e3 v3.0. I can get them to connect to the neopixel port And light up a strip of 17.but if I connect a second strip of 17 these do not activate.I am using klipper and changed the chain count to 34 but no luck.power and ground is connected to the buck converter and signal in neopixel port what am I missing
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Hi Bobby
What is an skr e3 v3.0. Googling comes up with a 3D printer board. Are you sure it is meant to drive neo pixels.
Cheers Bob
Hi mate
Yes is a 3d printer board.it has a dedicated neopixel port to drive neopixel
Hi Bobby,
Welcome to the forum 
Good to hear you’ve got the first 17 led segment working, that narrows down what the issues might be for the run of 34 a little bit.
Could you send us a photo of how you’ve got both strips connected? Another set of eyes might spot something small you may have missed.
The first check I would recommend to help diagnose the issue would be to try and verify the printer mainboard can deliver enough power for both strip segments.
Do you know the voltage and current rating the NeoPixel port can output for that board?
You can also do a quick test by measuring the between the voltage and ground at the far end of the LED strip, just to see how much the voltage is dropping across the length of the strip. If the voltage is low at the end of the strip, either your cable is too long or you’ve hit the current limit the port can output and the voltage has sagged as a result.
Another quick thing to check with these LED strips is that you’ve definitely got the second segment oriented the right way, WS2812bs have 3 contacts on both ends. Power, Ground, and Data In on one end and Power, Ground, and Data Out on the other. Do a quick check to ensure the Data Out of segment 1 is connected to the Data In of segment 2.
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Hi trent.i have the led running off printer psu through a step down converter.i have also tested power and ground at far strip is 5v and verified the arrows on strip are all facing the same way.i am going to test more tonight add a capacitor and a diode and see if any change
Hi Bobby,
Before you add more components or change the circuit can you please send us a photo of how the strips are currently wired up? A second set of eyes can may spot something simple you have missed.
One other test worth trying might be to swap the position of segment 1 and segment 2 to see if the fault remains the same or if both strips fail to light. If both strips work when they are the first one connected to the system it could help us isolate if the issue is with the strip itself or how it connected/addressed.
hi Trent
i didnt see this before i investigated,anyway i found a pin in the plug on the led strip was very loose so was making intermittent connectiom.however when i connected the capacitor it backfed the buck cionverter frying it.how do i stop this
Hi Bobby
Ahhh the pitfalls of randomly throwing capacitors around without knowing why. I have stressed the inadvisability of doing this on several occasions. You are usually only putting band aids around without fixing any underlying problem. What size cap was it and where did you put it. What did you do with the diode and what did you hope to accomplish with it.
I am surprised it fried the converter. If you had put the diode in the right place you would have prevented this “frying” but if it was a very large cap it could just as well been the large inrush current doing the damage. A capacitor (of any size) presents a short circuit at switch on. For how long is dependant on cap size. There again it could have been the buck converter design.
A wise bit of advice you should have heeded and save yourself a bit of heartache and $$.
Cheers Bob
By the way. I suppose your buck converter is capable of supplying the required current for the extra LEDs although it is funny that only the first 17 LEDs work. If it was a supply problem I would expect all the LEDs to malfunction in some way, not just the last 17.
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Hi Bobby,
It’s hard to say without knowing how it’s connected or what it’s there for. I am assuming your NeoPixel port is a 3-pin port that outputs 12V and a data line but I’m just guessing.
Could you give us a rough circuit diagram of how you’ve got everything connected in MS Paint? I’ve never used that printer mainboard before so if you could link some specs for it that would also help us get the context we need to give more useful advice.
Basically the printer power supply is hooked to a buck converter to reduce 24v to 5v,the out of buck is connected to the led pos and neg no board interaction on positive and negative,the signal to the led is board controlled through a 5v pin.the neopixel port has a power and neg also but is only rated to 2 amp that is y I went to the buck.here is a link to the board user manual.
Hi Bobby
That still doesn’t tell us anything about this capacitor and diode.
Cheers Bob
