RAMPS Max Fan Amperage?

I am putting a bigger fan on my Prusa i3, and I wanted to know if there was an official spec for maximum fan amperage. I know that the rail that supplies the fan power has to be a minimum of 5 amps, but I wanted to make sure that I won't be destroying anything with running a fan that can pull a max of 1.2A.
Any help would be much appreciated!

-Mike

No, you won't be destroying anything with such a large fan.

But honestly, it doesn't make any sense to put a 1.2A fan on the PWM output (D9) of your RAMPS board, because that output is usually dedicated to the layer fan, where a 40mm, 150mA fan is more than enough.

I suspect you just need to run your large fan at maximum speed or some constant speed less than that, so you might just as well connect it to the +12V directly and add a few 3A diodes in series if you need to lower its speed.

Your fan is supposed to cool the bridges, not blow them away !

Just kidding
-Olaf

Thanks for the reply! I'm looking for some more cooling power for my hotend, since with the extruder I have (Folger Tech), I can only print ABS for about 2.5 hours before it clogs from overheating. I had a remedy where I had my parts pause every 10-15mm in height, cool the extruder, then reheat it and continue, but it was quite a hassle.

I tried that fan out, turns out it was a bit too good for the job. about 10 seconds after I turned it on, my hotend dropped from 230C to 165C! I slower fan on there now, which is much more manageable. I'm just trying to get PWM to work now. Any M106 command, even M106 S0 turns it on to 100%.

Is this a layer fan, or the hot-end fan? The hot end fan cools the heatsink, and should have almost zero effect on nozzle temp. The layer fan obviously cools the print, but does nothing for the extruder . . .

? ? ?

- Tim

@ eovnu87435ds

I guess you want to cool down the cold end of your hotend.

However, you are using a canon to kill a mosquito here. My advice is to just do what everybody else does: use a 40mm fan directly connected to the 12V PSU. The RAMPS PWM fan output is for the layer fan, not for the hotend body fan.

Edited 1 time(s). Last edit at 06/25/2015 09:19PM by AndrewBCN.