Current limit of the white LED header on xbuddy extension board
Hello,
I am not particularly happy about the stock white LED stripe and would like to add my own lighting solution.
Can anyone tell me the current limit that the (white) LED header can handle? I'm not planning to add a ridiculous amount of LEDs, but I don't want to risk damaging my electronics either.
Kind regards,
Moritz
RE:
The schematic of the xBuddy extension board shows on page 8 that the white LEDs are driven by a MOSFET transistor, type MMBF170. The schematic also states specs for the transistor, but those seem much too optimistic -- current too high, on-resistance too low.
The datasheet of the MMBF170 transistor specifies 200 mA continuous current as the absolute maximum. Assuming that this is actually the transistor Prusa placed on the board, that's the limit I would go with.
RE: Current limit of the white LED header on xbuddy extension board
Hang on, here's another datasheet for an MMBF170. This one, from onsemi, has the better specs as stated in Prusa's schematic. I did not expect such significant spec differences for the same part number (from two brand-name suppliers). Let's hope that Prusa used the onsemi part or equivalent -- in which case you could actually get up to 500 mA for the LEDs.
https://www.onsemi.com/download/data-sheet/pdf/mmbf170-d.pdf
RE: Current limit of the white LED header on xbuddy extension board
Hello Jürgen,
Thank you very much! I totally forgot Prusa hardware is open source so I could check the schematics...
It looks like they are using either "MMBF170-7-F" (onsemi, 500mA) or MMFTN170 (diotec, 500mA) if I understand the text near the part correctly. So either way it seems to be 500mA - which still is a limit I'd rather not push, especially with SOT-23-3 which are not amazing for heatsinking.
But this gives me an upper ceiling to work with, and 24V 0,4A would still be 9,6W which is already more light than I'd realistically want inside a 3D printer. I mainly want to spread the light out a little (one strip top left, one top right, one where the original one is) to get more even lighting - helps noticing flaws or warping off the bed.
RE: Current limit of the white LED header on xbuddy extension board
Why not just use a separate power supply for your extra LED's? I did that with my setup. Even made a change to the xLCD mount to accept a small, inexpensive switch.
I posted all this here: https://forum.prusa3d.com/forum/user-mods/core-one-led-light-strips/#post-778387
RE: Current limit of the white LED header on xbuddy extension board
Why not just use a separate power supply for your extra LED's?
To get the benefit of automatic dimming?
RE:
No dimming. I don't need that - lights either on or off. Its an LED strip after all - so power consumption is not an issue. I also have a camera in the enclosure so having the extra light is a bonus.
RE: Current limit of the white LED header on xbuddy extension board
It looks like they are using either "MMBF170-7-F" (onsemi, 500mA) or MMFTN170 (diotec, 500mA) if I understand the text near the part correctly.
Oh right -- I should have read the small print... 😉
RE: Current limit of the white LED header on xbuddy extension board
No dimming. I don't need that - lights either on or off. Its an LED strip after all - so power consumption is not an issue.
Sure, but maybe longevity could become an issue -- depends on how well you can heatsink the LEDs.
RE: Current limit of the white LED header on xbuddy extension board
LOL! Longevity. These things are so cheap!! I could care less about that - just replace with a new one.
RE: Current limit of the white LED header on xbuddy extension board
LOL! Longevity. These things are so cheap!! I could care less about that - just replace with a new one.
Look, it's pretty straightforward: I am not trying to talk you into or out of something. Build whatever you like. I only gave a possible answer to a question you asked. Before you start insulting someone next, why can't you just leave it at that?
RE:
LOL! Longevity. These things are so cheap!! I could care less about that - just replace with a new one.
Look, it's pretty straightforward: I am not trying to talk you into or out of something. Build whatever you like. I only gave a possible answer to a question you asked. Before you start insulting someone next, why can't you just leave it at that?
I am not insulting anyone. I gave an idea - never said you must do it. I have that on my printer and I like it. But enough. I am not arguing with you, I have infinetely better things to do! 🙂
RE: Current limit of the white LED header on xbuddy extension board
Well, uh, that kinda escalated 🤐
Why not just use a separate power supply for your extra LED's?
That's a good suggestion, I have been considering it myself, but Jürgen guessed correctly - I don't want to lose the ability to have the LEDs software dimmed by the printer itself.
If 8-9W should prove insufficient, I'd probably add a small external PCB with a MOSFET that uses the LED connector from the printer board as a control signal. But I doubt that will be necessary.