Hello, it’s been awhile since I have installed a saber and I now have one of the newer 3.9 boards. I have a new saber in which I want to put one 5 mm RGB LED and two 3 mm LEDs, one in red and one in yellow. I’m seeing on the proffieboard website that the LED pads now can handle up to 30 volts. The LEDs I’m using go no higher than 3.3 volts.
My question is would I still need resistors for these accents or am I safe to proceed without them? I’m not sure if there are differences, if any, in regards to the wiring of accents compared the 2.2 version boards but space is at a premium in the neck of this hilt so if I can avoid needing to use resistors, that’d be great, otherwise I will probably just drop to the one RGB LED. The other two are more chassis accents so aren’t necessarily visible anyway unless the hilt is opened.
The LED pads are just MOSFETS, they pass through the raw negative wire. The voltage your LEDs see is defined by the positive. If you wire them the traditional way, i.e. directly from the battery, you will have a variable 4.2V to 3.3v. The LEDs have a certain margin, so people calculate the LEDs at 3.7v (the “nominal” voltage of lithium-ion batteries).
LEDs usually have forward voltage depending on color. That info should be available from whoever you bought your LEDs, but if they are cheap Chinese ones, just look similar in AliExpress.
From there you can calculate the resistors, which just need to be sized for the Watts of the LEDs on the line.
Well the manual I have already breaks down the resistors needed per color as 5 mm is a pretty commonly used LED. I see what you mean though that the resistors are actually on the positive not the negative so the LED pad voltage is irrelevant. With that I have my answer. Thank you very much!
One last clarification here, I actually just realized that the layout in the manual says the same thing for the version 2.2 boards about the LED pads also handling up to 30 volts. However to maintain NeoPixel blade effects and individual accent led effects at the same time, it looks like I would actually need to put the resistors on the negative side. Is that right?
Got it, thank you. I guess I’m getting some resistors. Might drop the additional chassis accents and just do the hilt RGB accent then. It is common anode btw. Knocking the rust off and want to keep it as simple as possible for wiring.
