Fan with PWM from filter unit how to hook up and address
I build the BRS CF80 Filtration Unit. Got 2 24V fans with it (4028's). Florent (the designer) advised me to use a MOSFET to power the fans and to use a signal line from the MOSFET to either the Pi (GPIO pin) or the Octopus Pro board to signal the MOSFET to run it. Is the Octopus Pro (which I have) capable of powering 3 40X28 fans, 1 part cooling fan (12V) and 2 coupled 24V fans. Or should I use a MOSFET?
17 Replies
Using the mosfet is to prevent overcurrent on any fan port.
You just need to connect 24v to the mosfet like any other and send the signal from a fan (or other PWM port to the mosfet) and set it as any other controllable fan on printer.cfg.
Don’t let the mosfet create any confusion because it is only an external switch controlled by any port on the board. It just avoids pullung too much current from the fan ports. And 2 c 4028 at 24v are too much for any fan port.
Thanks, I waited to connect it for an advise. You saved me from frying my Octopus Pro. Thx! I'll use the MOSFET and signal it from a free port. Can I still use the PWM the same way the 4028 part cooling fan is used? PWM wire connected to a pwm port? Or does the MOSFET limit it to on/off only? As far as I see it the MOSFET is the equivalent of the always on port but only switchable. Thx again!
The mosfet provides power, but the pwm will tell the fan how much to pull
Thx, got it! Now the only thing I've to figure out is the printer.cfg code, especially the pin names. I'll trace back the part cooling setup and pin names and copy the setup with the new pins .
I've been fighting with the connection all afternoon. Got the MOSFET hooked up to the 24V and the fans on the output. For the switching I tried using one of the Octopus Pro endstop pins (Octopus Pro 446 J34 pin PG15). MOSFET wouldn't switch. Whatever I tried no luck. One wire to the bed - , to the bed + ground connected to the mosfet no joy. Basically what signal should I use, I read on discord to use a PWM signal, that would be of one of the fan ports right? Any advise on this? Now I have hard wired the fans to the PSU directly which leaves the fans on as long as the printer is powered. I'd prefer them to be switchable. Does a MOSFET like this one need a 5V signal to switch? Any help is welcome.
Got a picture or diagram of how you have it wired up?
Tried all 3. The PG15 gives a steady 3.2 V
I read that similar MOSFETS need a 5-24V signal to switch, so maybe that's the thing. I guess it needs a 2 wire setup from signal pin to Bed + and gnd to Bed -. The signal pin coming from a PWM fan port since that generates a 5V signal. If anybody knows please guide me in the right direction.
Sorry, can you label those rectangles? I'm still not sure what I'm looking at :/
Middle rectangle is the MOSFET, bottom one is the Octopus Pro, Top 2 are labeled
got a link/datasheet for the mosfet board?
ANGEEK 3D printer Heat bed Printhead heating control MKS MOS module...
ANGEEK 3D printer Heat bed Printhead heating control MKS MOS module super large MOS tube 30A
Is the designer really recommending to use an external MOSFET driver to power the fans? Why not use fixed 24V directly from the PSU and just use the PWM to drive the speed, just like the part cooling fan?
He is, because the 2 4028 24V fans would draw a too heavy load on the boards fanport and possibly fry by overload the 24V rail of the board. Problem was too have the MOSFET switch on and despite a days and nights long search on Google there's no documentation on CNN connecting the MOSFET to another device than a hotbed. latest info points me to the endstop signal pin being Digital and connecting that to the "SIG" port of this MOSFET which is designed for a digital signal.
Could you use the heater port for power, and the usual pwm pin?
The external mosfet is quite an ovekill and unnecessary IMHO. I would connect the 24v of the fans to either an unused bed heater port on the board (as @TheTik suggested) or directly to the 24V output of the power supply. And then you drive the PWM to control the speed. If you connect to the bed port, you need to make sure the voltage levels are s you expect them to be, so that you get a reliable ground reference. That is why I might suggest using the ground an 24 directly from the power supply, no need to worry about the levels. I’d also connect the ground to as close to the board as possible, to make the ground reference the same as what the board has.
Excellent advice however I got the PWM part of the fan wrong. It's a 3 wire fan. The third wire is a tacho. It won't control the speed. To be able to switch it on and off is worth a lot. The bed heater port can do that. In the mean time I'm going to search for payable PWM 24V 4028 fans. Thanks for your advice.