Air filtration fan FAN3 on the xBuddyExtension board
Hey everyone! I've had my Core One L for a week now, and everything is awesome so far 😊聽
My next step is to connect the chamber exhaust to a custom air filtration setup. The exact details of that are not relevant, so I'm skipping over them for now. However I do have some questions with regards to xBuddy / xBuddyExtension electronics and software logic, which will be of interest for a lot of others that go into similar directions, I think. Here are my questions, numbered for easier referencing:
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1 Electrical questions:
- 1.1 The original "Intel CPU cooler spec" https://glkinst.com/cables/cable_pics/4_Wire_PWM_Spec.pdf says the mainboard should have a pull up to 12V on the tacho signal. From https://www.prusa3d.com/downloads/Electronics_drawings/MK4-xBuddyExtension-06.pdf (page 12) I get the tacho signal is pulled high to 3.3V on the xBuddyExtension board, with a protection (BAT54KFILM) against external pull-ups to higher voltages, correct?
- 1.2 The xBuddyExtension schematics show a https://assets.nexperia.com/documents/data-sheet/BUK6D120-40E.pdf 3A capable FET as the high-side switch on the 24V line to FAN3 (EXT_POWER_FAN). What is roughly the max safe, continues current draw, during printer operation, on the FAN3 connector? So I can decide if I need an extra PSU for my solution, or if I can pull the power from the xBuddyExtension board.
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2 Logic / software questions: I have not tried / used the air filter on the Core One (L) before.
- 2.1 Are the chamber fans logically linked to the air filtration fans? I.e. if the chamber fans run, then the air filter fans run as well.
- 2.2 If >yes< how is the link done? I.e. same set RPM maybe?
- 2.3 If >no< what is the general idea on how a user should set this up? I.e. fixed air filter RPM for the entire print, or custom G-Code, etc.
- 2.4 If the RPM on FAN3 is set to 0, will the 24V output on the connector be shut off?
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I did some searching through the forum and couldn't find something on the above, but I probably just didn't put in the right searches 🙃聽
Anyways thanks to Prusa for a great printer, and any answer in advance!
RE:
Update on my question 1.2: I had a closer look at the MK4-xBuddyExtension-06.pdf schematic. There is a TPS16630RGER which is a configurable current/power fuse, with current measurement capabilities. If I followed the datasheet correctly, the xBuddyExtension has this configured to about 4.6A max, and its on the 24v rail. So this places an upper current limit on the entire board (5V and 3.3V on the board is derived from the 24V rail). This chip also offers a measurement output of the current going through it ("IMON" pin), which goes into the STM32 uC, that reports back to the main (xBuddy) board, that eventually shows this on the front LCD (under sensors).聽
So what is connected to the xBuddyExtension board:
- Chamber fans (these are 24V directly, and draw about 600mA on 100%).
- RGB led strip for lighting (about 100~200mA on 100%).
- MMU (don't have one, can't test).
- One other fan (not sure what that is).
- USB power delivery (not sure what that is for)
The current displayed in the UI also includes the print head heater, but its not connected to the xBuddyExtension from what I can tell. So I assume the displayed value adds in other sources. For me it idles around 0.5A with nothing running, and lights dimmed. This sounds a bit much for just the STM32 uC and assorted bus drivers and such, which again points at more things being summarized into this one value.
So from this I guess that an about 1A draw for FAN3 should be in budget, depending on what else you connect, maybe even more (or less with MMU attached) ... Hope someone from Prusa can confirm this ballpark estimation 😋聽
RE:
This post shows the fan that Prusa drives on Fan3. Alveo3d lists a similar one, BLHP2432-H24, at ~24W at 24V. To quote @_kaszpir 's good advice,聽
"Of course this needs additional confirmation, so for now you fry the hardware on our own." It looks like you're doing a good job on the research, keep us posted on the project.
RE: Air filtration fan FAN3 on the xBuddyExtension board
@ssmith Oh cool thanks for pointing this out! 24V 4pin PWM fans are rare, I just bought one of those to test 😆
I also now had a look at the Molex connectors used (151350403) and those have a max of 2A per contact. This gives a reasonable upper limit for the FAN3 connector I think. Some confirmation from Prusa would be nice, but I guess this mostly covers Q1.2 for me 🙃聽
Will keep you posted about more findings 👍聽
RE: Air filtration fan FAN3 on the xBuddyExtension board
I have seen posts indicating the Prusa fan is 24v 0.5A and the max is 1.0A, but no true source.
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From my understanding, when you enable the menu setting for the advanced filtration.
"Note: When enabled, the Advanced Filtration System also takes over chamber temperature control and disables the cooling fans (with the exception of critical overheat situations)."
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As of 6.4, you can now control the chamber fans with G code
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M147 (Set): Explicitly marks the current print as requiring chamber filtration, overriding the automatic behavior based on the filament parameters.
M148 (Unset): Explicitly disables chamber filtration for the current print.
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Firmware 6.3.1 added the DIY fan option, detailed here
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