UMO Fan Circuit

[the_schire 3]

Hey I'm working on an e3d v6 conversion, and I'm wondering about how much current I can pull from the stock fan circuit. I plugged two 12v 0.1A fans (wired in parallel) and they didn't start spinning until 91% power, so I worry that they're drawing a lot of current from the circuit. Does anyone know the limitations of this circuit? 

[JohnInOttawa 22]

Good morning.  The E3d mod and fan mods have both been done to the UMO by others here, hopefully you'll hear shortly.

 

I've only had to repair my UMO PWM control (transistor) and am still using the original fan.  That said, you might find the following post starts you in the right direction.  The board sends 19V to the fan, so not all 12V fans will work.  As I understand it, even in parallel, you might need to manage the voltage down.

 

Presuming for a second that the fans can handle the voltage, there is normally a pretty high threshold to start rotation, after which the setting can be dropped.  Your post doesn't say whether you experimented with lowering the power from 91% to, say 50% once the fans were running.  If they keep going and the speed lowers as requested, that would suggest that you have control of them and there is just startup to tweak.

 

Good luck

 

J

 

 

Edited July 26 by JohnInOttawa

[the_schire 3]

On 7/26/2018 at 3:30 AM, JohnInOttawa said:

 I've only had to repair my UMO PWM control (transistor) and am still using the original fan.  That said, you might find the following post starts you in the right direction.  The board sends 19V to the fan, so not all 12V fans will work.  As I understand it, even in parallel, you might need to manage the voltage down.

 

 

In practice, I think most computer fans can take a lot more than their rated voltage due to the simple nature of their circuits. I have a friend who pushed a computer fan to over 25v before it blew up. As for longevity, I broke the original fan that came with my printer, so I got a new 50mm fan rated for 12v. It's been working fine for a few years now.

 

I did notice that the motor of the 30mm hotend fan got rather toasty when given the full 19v, so I wired a few 330 ohm resistors into the fan lead to drop the voltage and thus the heat. 

 

What I'm really worried about is how much current I can pull from this circuit before something on the main board fries. If I were to guess, maybe 1 amp? However, I wanted to double check before I killed something on an expensive control board. 

Quote

Presuming for a second that the fans can handle the voltage, there is normally a pretty high threshold to start rotation, after which the setting can be dropped.  Your post doesn't say whether you experimented with lowering the power from 91% to, say 50% once the fans were running.  If they keep going and the speed lowers as requested, that would suggest that you have control of them and there is just startup to tweak.

That's good to know, I'm not sure if I tried that. I usually run my fans either off or 100%, but if 100% will fry a transistor, that's a good tip, thanks.