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
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.