Fans not working after shorting fan leads *solved*

[WTFockewulf 21]

Hi Guys,

I have a very annoying Problem with my UM2. Due to a faulty duct (it broke during an overnight print) one fan came loose and the cable got smoldered thus causing a short circuit. After this, the (new) fans would only run on 100%. between 01 and 99% they would only "quiver". I replaced the 817 Transistor and when I measure the Voltage you can see it go up nicely to 24V as I increase the steps in the menu. But again, the fans only start up at 100%...

Any Ideas are much appreciated...

Rgds,

Philipp

Edited December 16, 2016 by Guest

[neotko 1,417]

Wow the problem persist after changing the 817.. I'm clueless. Can you plug the led on the fans to see how the respond? Maybe is the actual fans the ones that died?

The leds use the same v so if they work the same way the cheapest solution could be to change the led to the fan making a custom firmware and changing the pin.h assign table.

[neotko 1,417]

Oh I see you replaced also the fans? Umm try the led on the fans to see if the pwm works. Maybe the fns you got ain't PWM-able? Are they from UM resellers?

[WTFockewulf 21]

Yep, I changed it but no avail. i have a couple more so maybe I just managed to get a faulty one. I will change it again. But I will use the LED's to cross check.

Both Fans are new, but I cross checked with a pair of working ones from my secon UM2. Same story so the fans are definitely OK.

[WTFockewulf 21]

Oh I see you replaced also the fans? Umm try the led on the fans to see if the pwm works. Maybe the fns you got ain't PWM-able? Are they from UM resellers?

 

OK, I wired up the LED to the PWM and it works perfectly. I can regulate the brightness of the LEDs with the FAN control. Fans wont work on the LED control though...

Is it possible that the little controller in both fans could be shot? The other fans are not original UM. Best guess is these are not PWM fans... Would make sense. Seeing the cables of one of mine are cooked, where can I get replacement fans?

[WTFockewulf 21]

Right, hooked up the working original fan to the board and it works...

So the question now really is where to get new fans. Looks like both are shot as is the cable somewhere along the line.

[neotko 1,417]

Any UM reseller have them. I think they are 10-13€ each? I bought a couple a few months ago.

Nice at least the board is ok now that you fixed it.

[WTFockewulf 21]

Any UM reseller have them. I think they are 10-13€ each? I bought a couple a few months ago.

Nice at least the board is ok now that you fixed it.

 

Neotko,

yes, very glad the board is fixed. I will order the fans tomorrow. Hope they arrive quickly, I have customers waiting

Rgds and thanks for the help, its much appreciated!

Philipp

[SyntaxTerror 344]

Best guess is these are not PWM fans...

 

Technically speaking, none of the fans in the UM2 are PWM fans; that would require a third lead for a triggering signal. The UM2 runs ordinary DC fans as PWM fans by chopping the power input. Not all fans react equally well to this, and the PWM frequency may be the issue here.

[neotko 1,417]

 

Best guess is these are not PWM fans...

 

Technically speaking, none of the fans in the UM2 are PWM fans; that would require a third lead for a triggering signal. The UM2 runs ordinary DC fans as PWM fans by chopping the power input. Not all fans react equally well to this, and the PWM frequency may be the issue here.

 

It would be interesting to actually know what specs an user must search for, to have fans that work on um2 boards.

[SyntaxTerror 344]

Agreed, there's an annoying lack of specs regarding fans (airflow/pressure/etc).

I've been wondering awhile whether or not there's anything to be gained by replacing the side fans with thicker ones for greater pressure. I have this sneaky suspicion that angling the airflow as aggressively as it is done on the UM2+ head assembly might severely limit the airflow due to lack of static pressure.. the fans are awfully thin after all so I can't imagine they produce much. Then again I'm not that sort of engineer, and airflow is a surprising thing sometimes so I can't say for sure. I'd like to try to replace them with something else, but it gets somewhat random when you don't have any specs to compare with.

Regarding the PWM issue, it would be a quick modification to replace the fans with proper PWM controlled ones, as long as we have access to the PWM output and a suitable power bus. But again, with no fan specs, it would be random experimentation.

[neotko 1,417]

Agreed, there's an annoying lack of specs regarding fans (airflow/pressure/etc).

I've been wondering awhile whether or not there's anything to be gained by replacing the side fans with thicker ones for greater pressure. I have this sneaky suspicion that angling the airflow as aggressively as it is done on the UM2+ head assembly might severely limit the airflow due to lack of static pressure.. the fans are awfully thin after all so I can't imagine they produce much. Then again I'm not that sort of engineer, and airflow is a surprising thing sometimes so I can't say for sure. I'd like to try to replace them with something else, but it gets somewhat random when you don't have any specs to compare with.

Regarding the PWM issue, it would be a quick modification to replace the fans with proper PWM controlled ones, as long as we have access to the PWM output and a suitable power bus. But again, with no fan specs, it would be random experimentation.

 

A bit offtopic, but, since you mentioned it. I think the best alternative atm is @Gudo fan system

https://www.youmagine.com/designs/35x35-12vdc-um2-family-centrifugal-fan-shroud

Curiously @Gudo uses the 24V of the same fans UM did use on the UM3 (UM uses the same model but 5V version on um3). Also his design is much more centered airflow-wise. So the air should be pretty nice.

[SyntaxTerror 344]

Ah, I thought they might indeed be radial fans on the UM3. Just never could tell what was really going on inside the head because of all the covers hiding the inner workings. And you're right, that looks like a very nice design. Might just have to try it out.

Edited December 13, 2016 by Guest

[WTFockewulf 21]

Right, FWIW, my UM2 is working again.

After changing the 817 I first bought a set of Sunon Maglev MC30101V2-0000-A99 Fans. They do not work with the board. I then bought some cheap fans from here:

Click me softly and they do the trick although they have the same specs as the more expensive Sunon ones... go figure.

Both are brushless, both are 12V...

[SyntaxTerror 344]

After changing the 817 I first bought a set of Sunon Maglev MC30101V2-0000-A99 Fans. They do not work with the board. I then bought some cheap fans from here:

Click me softly and they do the trick although they have the same specs as the more expensive Sunon ones... go figure.

Both are brushless, both are 12V...

 

The problem here is that these are DC fans and as such, have their own internal circuits for switching the stator windings on and off in order to make the rotor spin. What we're doing when we try run them of a pulse width modulated fan bus, is turn the entire fan (and thereby the switching circuits) on and off at an alarming rate. It won't necessarily work on all fans, and is often dependent on the PWM frequency.

A DC fan designed for PWM operation is supposed to be powered on all the time, and instead takes the PWM signal on a third wire - and the fan electronics never lose power.

So yeah, it's hit and miss with this sort of thing. Most normal DC fans can be run with a PWM signal just fine, provided the PWM frequency is low enough. Ideally though, you would want to move the frequency somewhere above 20KHz since a great many fans will appear to become much louder when switched with a frequency inside the range of human hearing. Unfortunately not all fans react equally well to this.

[SyntaxTerror 344]

Oh yeah, one thing that should also be mentioned in a fan replacement thread is that when getting replacements for these two fans, you should make sure they have ball bearings. Sleeve bearings won't last long when operating the fan on a horizontal plane.

[WTFockewulf 21]

Thanks for the Input. These are ball raced according to the product description.

Truth be told, I am quite suprised These DC brushless fans work with PWM at all. The little controller must initialize first, check the position of the bell and then power up... and all this pulsed many times per second. I work a lot with brushless motors in my rc hobby and thats a lot of work for the ESC to do. Thats probably also the reason why the UM Board has a short 100% pulse when turning the fans on. Its easier for the ESC to determine the RPM of a moving bell.