Re-wiring X1C logo LED’s downwards in print head front cover housing

My dear X1C enthusiasts,

I made myself a little project and could use some help and thoughts. The logo lighting of the X1C print head is very nice but not very useful. Since they are made of three very bright LEDs and can be turned on and off by G-Code, I want to move them downwards in the print head front cover housing to illuminate the tip of the hot end and build plate underneath.

I already implemented the G-code in my own printer setting files / machine code templates (M960 S5 P1 to turn on logo lamp and M960 S5 P0 to turn them off). I moved to M960 S5 P1 code to the very end of the machine start G-code so that the 3 logo LEDs stay off and do not interfere with LIDAR measurements. Then turn them off again with M960 S5 P0 at the very end of the machine end G-code.

I ordered a spare X1C font housing to test and try the rewiring of the LED’s. Also I ordered new wired micro LEDs so I can eventually remove the original LEDs an replace them with wired ones that I guide downwards. I’m still figuring out how to neatly do this inside the bottom part of the turbine output holes.

I also had the idea not to remove the original LEDs but add 2 LEDs on wire to the appropriate terminals of jumper 7. But I guess that this will mess with the 3 original 560 SMD resistors on the PCB board. The two LED’s that I add with just connecting them the two appropriate jumper pins, won’t have a resistor. I guess that is not good for the LED’s. I can’t figure out the wiring schematics so I asked Bambu Lab if they are willing to provide me with the wiring schematic of the front cover PCB. That would make it a bit easier. Or maybe some of you already figured that out. I Also asked if they maybe provide me with a spare PCB that doesn’t have the three logo LEDs on them. But that asking for a stretch, I guess.

Other ideas are also welcome by the way to finish my goal. Maybe I’m addressing this from a completely wrong way :blush:. When I have a working procedure, I’ll document every step by photo and text and post it in case somebody wants do execute this mod too.

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LEDs need a series “current limiting” resistor to keep them from overheating and burning out. The LED will have a current rating, like “50mA”. And also a voltage rating like “5V”. If you were going to power such a LED you’d need a resistor who’s value would cause only 50mA to flow.

Ohm’s Law says Volts = Current * Resistance. In this case we want to calculate Resistance, so we’d use the equation Resistance = Volts / Current. Volts is 5, current is 0.05, so Resistance is 100 Ohms. So to power the LED with a 5V source, you’d connect a 100 Ohm resistor in series with the LED. Doesn’t matter if it’s “high side” (between the connection point and the LED) or “low side” (between the LED and ground).

So what you want to do will work fine if you add these resistors to your LEDs. But you need to know what the drive voltage is that the X1C is using (could be 3, 5 or 12V for example, and you need a LED that’s rated for that voltage), and you need to know how many milliamps your LED needs. Then you do the math above to compute the resistor values you need (and note, you can round off to a value that’s close to what you calculate if you can’t locate the exact value. A few percent either way won’t make any meaningful difference).

If I was going to do this, I would look for a LED ring to go around the whole nozzle. Something like this (except this is a “smart” LED ring, you have to control them with a micro controller). The hole in the center is about 1", but there are all different sizes. I would use a really small controller like a ATTiny85 to drive the LEDs. And I would connect the print-head LED power source to an input of the ATTiny85. Then, I would write a little code that detected when the print-head LEDs were on using that input signal, and it’d drive the LED ring. Would let me do colors and vary the brightness independent of the simple on/off control the print-head implements for its LEDs. I could do spooky effects for the timelapse, with the color changing over time.

I’d note, I was already considering this idea. I don’t like the quality of the lighting in the printer. Makes it challenging to see what’s going on in the far corner of the print bed. Particularly with darker colored filaments.


Hi RocketSled, thank you for the very in-depth explanation. That is so nice of you to share with a complete novice person. I think I go for the option to just move the three existing LEDs with wire down. That way I keep everything within the front cover and by doing so, replacing the hot ends as easy as possible.

I measured the voltage going through the LEDs with my multimeter. It’s 2,65 volts. Awh…I hope i ordered the correct ones at amazon.
I had a test PCB from an old lamp with some LEDs on it just as the PCB in the front cover has. Trying to de-solder them is a PITA…if you catch my drift :wink: They melted.

I could just snap the LEDS of the front cover PCB, clean the terminals en solder the wired new LEDs to the terminals. That is, if I don’t accidentally damage the terminals bij snapping the LEDs of the PCB.

The ring LEDs you propose look real super cool. The lighting they will give would be awesome I Imagine. But for now I’m afraid that this is a bit to difficult for me as a novice. Also I placed a 30cmx30cm led panel on top of my X1C. The lighting is really wonderful and bright everywhere inside the cabinet…except under the hot end/ printhead. So I do not need a lot of additional light under the print head. The light of the three logo LEDs wil be more than enough.

I’ll keep you posted here and share my next steps and thoughts. Hopefully you’ll prevent me from making my X1C go BOOM! Just joking :slight_smile:

Thanks again for your in-depth info!

Warm greetings from Ludo Timp, The Netherlands

Also I had another thought: what would happen if I solder a wired LED directly to an existing one on the PCB? Is the one resistor connected to the original LED than enough to carry the second LED? Will the LEDs just dim half in brightness because the voltage will be divided in two over the two LEDs?

Is there a way to see on the soldered LEDs on the PCB what model they are so I can order them somewhere online? I don’t see any writing on them. I think I ordered the wrong ones now.

The reason the light bar thats included isnt brighter is because it would interfere with the lidar.

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I placed a LED panel of 30x30 cm on top of my X1C, the kind that one normally mounts at the ceiling of the kitchen. It’s very VERY bright! I experience no problems with lidar measurements whatsoever.

If its above the lidar and print head, the lidar is probably scanning a shadowed area. Nice though. And good to know because I want to add an led strip around the lid.

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Each LED needs its own resistor. If you put two in parallel on the same resistor, each LED gets 1/2 of the current and it will not be as bright as it should be. Since sensitivity to light isn’t a linear thing, 1/2 the current may be much less than 1/2 the brightness.

Based on your measurements with a meter, it looks like you need a 2.5V (or thereabouts) LED, though a 3V would work. Anything higher will not be bright enough.


That’s why I want to use the three logo LEDs and move them down. You can turn them on and off by G-code. I already added machine G-code to the start and end. This in case the LEDs are accidentally on, to turn off the LED’s while the lidar is in use, to turn them on when the printing starts and to turn it off again when printing is finished.

Thanks! Very helpful. :slight_smile: The white wired LEDs I bought are 2,8 to 3,3 volts. They have a brightness of 240 to 280 MCD. So I guess that if I solder the new wired LEDs parallel to the existing ones on the PCB, the brightness dims by half, at least. That exactly not the goal I wish to reach. So I guess removing the old ones and soldering the new wired ons to the pcb is the better option? If I know what LED’s there are now on the PCB. I already asked Bambu Lab. Hopefully they can provide me with a model/part number or exact LED specification.

Not sure I understand why you need to remove the existing LEDs. Just buy a few resistors for the LEDs you’re adding and leave the stock Bambu LEDs in place. If you’re confident enough of your soldering skills that you feel you can safely remove the existing LEDs, instead just tack a wire on to the “high side” of one of those LEDs, add 3 (or however many) resistors you need for your added LEDs, connect all three resistors at one end to your tacked on wire. At the other end of each resistor, connect one LED (or just use one resistor with 1/3rd the value calculated using my formula above). Tie all three of the cathode side of the LED together, and wire that to electrical ground and as Emeril would say… BAM. :slight_smile:


I’m a complete novice…I have no clue what you mean from ‘High side’ on. That is why I go for the replacing option so I can skip the resistor, calculating and ground challenge. I understand your totally good intentions but its still gibberish for me. I have no clue what my soldering skills are. I know that I’m carefully though and have the right equipment. That’s a good starting point. I see that without hands on guidance, I’m a bit lost.

Who’s Emeril? Or is that an expression? :slight_smile:

In this screen clip of a schematic for a project I’m working on:


The “high side” of the LED is the positive (Anode) side. This is the side from which current flows in to the LED. The “low side” of the LED is the negative (Cathode) side. That side connects to Ground.

Note that in my project, which is battery powered, I have used fairly large resistors to limit current to the LEDs. They’re dimmer, but my battery power will last quite a bit longer than if I let them draw what they want for full brightness.

Also note that I show the current limiting resistor on the “high side” of the LED, but it works the same if it’s between the cathode and ground.


Pure LEDs have a forward bias voltage somewhere between 1 and 4 volts. That is the measured voltage difference on the LED when it is lit. So, to calculate the resistor needed to limit the current to the desired value, you need to substract the forward bias voltage from your supply voltage.

R = (Vsupply - Vforwardbias) / Current

Example, to get 50 mA in an LED with a Vfb of 1.8V from a 5V supply:

R = (5 - 1.8) / 0.05 = 64 Ohms (note: not 100 Ohms as you stated)

Then, make sure your resistor has a power rating high enough to dissipate the heat it will generate
where P = R * I * I
in example
P = 64 * 0.05 * 0.05 = 0.16W

Yes, I know. But those additional details only confuse the people who don’t already understand this stuff. I simplified. I’m assuming the LED is rated for the same voltage as the Printhead supplies, which looks like it’s 3V or so. So use a 3V LED. In that configuration you just need to consider current.


Hi Randy, thank you again for the explanation. You are very kind and very helpful to share your knowledge with me, someone who has almost zero experience with electronics. Because of your help my learning curve get a bit higher. I’ll do my best to wrap my head around it and see if I can implement it in my next steps. :+1:

Hi byMH62, I’m afraid your explanation is way above my pay grade. I really do appreciate your help but I’m so novice that I do not understand what you write. Thank you that you are willing to share tour knowledge. I hope that in the future I can refer to your information again and understand what you’re trying to explain. :+1:

Hi Randy, your absolutely correct and I really appreciate your sense in that and adjusting your information to my level of knowledge. I do however appreciate the help of byMH62 and hope that one day I’ll understand what he’s trying to teach me. Sharing information is always a good practice.

The LEDs I ordered are 2,8 tot 3,3 volts. So in that step I succeeded 100%. I ordered them at Amazon and they will be delivered sometime next week. To prevent you from doing everything I propose that I prepare the next steps, regarding the electronics, make foto’s of it and ask here on the forum if my thoughts are correct before I start soldering etc. I’ll keep you posted. If you maybe prefer to communicate in another way, please let me know.

Thanks again!

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Hi Randy, just for my simple mind of understanding. Can you explain the following?
When a LED is rated for getting a voltage between 2,8 en 3,3 volts and the power it receives is 3 volts, why is it then necessary to put a resistor in the voltage supply? It gets the right voltage it needs.

I have a Christmas led string at home for instance, 80 micro leds in parallel, powered bij 3 AA batteries. There is nowhere a resistor present. For small project I always use those, just cut away the leds I don’t need, and attach less batteries. For that I calculate the 80 leds divided by three. So if I cut away 26 leds, I also remove one battery. You probably laughing out loud right now by my simple way of thinking but t worked in lots of situations. And there is nowhere a resistor to discover. So Randy, do you magic stuff and explain me once and for all that there’s more to it. And I wil go as Emeril: BAM! :smile: (you teached me an English expression I didn’t know, thanks for that! :slight_smile: )

Oh wait, I’ll share my next thought too. I think I’m giving my own answer. The voltage the X1C gives to the front cover PCB LEDs is 5 volts. Is that correct? But the transistor reduces it to 3. That’s why I measure 2,65 volts when I measure the LED with my multimeter and place the multimeter probes to the anode and cathode of the LED. Are my thoughts correct? Where do I place the probes on the PCB to measure the real provided voltage?

In the first photo you see what my goal is, the second photo is the back of the pcb, the third is the front of the pcb.

I observed the pcb with a magnifying glass but it’s very difficult to see how al the traces run and are connected to each other. I also suspect that they go, at certain points, through the pcb from the front to the back.

And another thing: why not just provide the LEDs with 3 volts on the pcb? That way you can eliminate three resistors = cost reduction. Again, you’re aloud to ROFL. I know, novice thoughts…so simple. :rofl: