Bento Box wiring using the chamber fan connection

[mge]

I recently added a Bento Box on my X1 Carbon printer and I spent quite some time on forums to find the best way to wire it. I ended up doing something on my own so I share it here, as I think it could be useful to other users!

To power the bento box, I used the chamber fan connector. I never use this fan as it provides very poor VOCs filtration (it mostly expels smelly air into the room) and I mostly print in ABS / ASA so I don’t need to cool the chamber.

I used the “FAN_1” connector, initially used for the “Chamber Fan”. For the original fan, the wiring is as follows: black = 24 V, dark gray = GND, light gray = tachometer, white = PWM.

I disconnected it and plugged a new custom 4 pins picoblade connector, wired as shown on the schematic below. I used a mosfet with a gate resistor to power the fans, using the PWM signal and I also added a flyback diode. I indicated the components I used but they may not be optimal for this application: I used components that I already had from another project. I did not use a pull down resistor on the gate of the mosfet because there is already one on the MC board. I added a gate resistor but I’m not sure that it’s really useful. A 20 Ω resistor is already present on the MC board, but it seemed quite low to me so I added a 220 Ω one. I always run my fan at 100 %, so I don’t care about the switching time of the mosfet.

To route the wires, I used a small gap between the aluminum case of the X1 and the back plastic wall, to take my wires outside of the chamber. Then I routed them along the other cables, at the bottom of the printer.

The advantage of this solution is that it does not require any modification of the casing, and the fan can be controlled using the M106 P3 SX (X between 0 and 255) g-code, or even using the GUI, as it’s routed to the chamber fan. However, if I turn on the chamber fan, after 2 seconds the speed shows 0 %: as my fan only has 2 wires, the tachometer pin is not connected, so the printer thinks the fan is not turning. It’s juste a display issue so it doesn’t bother me too much. Another drawback is that I can’t use the real chamber fan, but that’s totally fine to me as I never used it before. If one day I change my ming, It can very easily use it again.

I modified my printer profile to add the command “M106 P3 S255” at the end of the start g-code and the following commands after the end g-code:

M106 P3 S255
G4 P300000
M106 P3 S0

This code will turn on my fans during all the print, and keep them active during 5 minutes at the end to thoroughly clean the air of the chamber. Since this modification, there is almost no smell during my ABS / ASA prints.
The noise of the fan is nearly inaudible when printing, as the printer already makes a bit of noise. I could also use lower values for the PWM, but I want the highest airflow to have a good filtration. I also noticed that my fan don’t work well with lower PWM values. Below a PWM duty cycle of 90 %, my fan won’t turn on. Anyway, I always use them at 100 % to have the best filtration so it’s not a problem.

[PrintMint]

Do you only use one fan for this? or still the two? also do you mind linking the components you used? I like this idea.

[mge]

Hello,
I use the 2 fans for this. The 2 fans are connected together inside the bento box. I don’t have specific links to share for these components, I just took components I had around, I don’t remember where they came from. Also, they may not be the optimal components, or at least there are plenty other components that will work as well as these.

[mge]

Review after a few months:
After printing a few spools of ABS or ASA, I’m not entirely satisfied with this bentobox. During long prints, there still is a quite strong smell in the room, which is not good at all.
I tried removing the HEPA filter to increase the air flow as it seemed very low to me. I did not see much improvement after removing it. I also removed some carbon pellets from the bentobox, and it improved a bit the filtering (less smell). I first filled the box up to the mark, as indicated in the bentobox manual, but it seemed to be too much, it was reducing the air flow too much, resulting in a poor filtration.
I doesn’t seem to be related to my wiring setup, as the air flow was similar with an other power supply.
I think I will try replacing this setup with the Nevermore Mini, or even the Nevermore Stealthmax (if I find a way to install it without drilling a hole in the X1C frame).

[Mcnugget]

Have you tried the 4028 fans? The voxel one suggests those and not 4020 for asa/abs.

[Advocado]

You should try and build using 4028 fans.

While Bentobox doesn’t eliminate the smell completely - it does help a lot.

[Mr.Bang]

I saw an alternative (even if you said, that you don’t need/want to cool your chamber):
it’s a magnetic cup to place 2 HEPA filter (same like bento Box) on the outside vent in the back.
(can’t post links here)
Since that uses the big original fan, it could be more effective. (but has no activated carbon, guess it could be upgraded with minimal effort.)