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Nicolinux

UM2 hotend side fans rating

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Hi,

Anybody knows the rating for the side fans on the hotend? (not the always on fan).

I tried to replace one of them with this fan, but then the other original fan acts up so I guess the difference in rating isn't that healthy...

 

 

Stefan

 

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Hi Nico

Regular you can find specific information on the bottom of the original fan, is there nothing to see? There is only one regulated fan-cable, so always have two fans are mounted with identical characteristics, otherwise You produce an imbalance in the fan performance. Your eBay fan is actually not OK, use two identical with 12 Volt. Only the rear fan use 5 Volt. The other characteristics of the eBay fan are OK, only You need a 12 volt variant.

Here is an example of a compatible fan:

eBay-Artikelnummer: 390883623144 / Link: http://www.ebay.de/itm/390883623144

Markus

 

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Oh, maybe I have a good idea for the rear UM2-fan:

The functionality can be improved without complicated electronics. There are bimetallic switches which can close / open a circuit, for example, at 40 degrees. There are also very small sizes of these bimetallic Switches. With such a switch near the heat source (HotEnd) so the fan can automatically be silenced. Once the Hotend is not in a critical temperature range, there is absolute silence fan. If interested, you can ask Philip times, I think that he knows these things already.

Explanation: http://de.wikipedia.org/wiki/Bimetallschalter

TypeSearchLink: https://www.google.de/#q=TLRS-9700%2B40

Link: http://www.amazon.de/gp/product/B00HK8YE3O

Markus

 

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Oh cool, I didn't know about these.

But the 3rd fan problem is solved anyway. I have replaced it with http://www.ebay.de/itm/Lufter-5V-0-38W-25x25x6mm-3-7m-h-23dBA-Sunon-MC25060V2-A99-/231085070846 and now it is almost completely silent. That was the reason I wanted to tackle the side fans. I thought I could simply buy the same fans but just the slightly bigger version. Should have asked about the power rating first :/

 

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Hi,

I'm trying to replace both side fans at the moment to see if I can reduce the noise level (especially at low speed). Since I replaced the rear fan with a quiet one I can now hear the side fans produce a high pitch sound at low speed and its very unpleasant.

I did get 2 12V fans and connected them but it wont work. Even at 100% the fans dont start.

http://addison-electronique.com/catalog/product/view/id/18839/s/ventilateur-12-vdc-30mm-x-10mm/

The fan themselves work because if I leave one of the original one and prevent it from spinning the other one starts and run at full power.

Any clue what could cause the fans not to run? I can feel the tension going in the fan and sometimes see the fan trying to start but with no luck.

 

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Perhaps i missed this... but... have you beared in mind that not every fan is pwm-controllable..?

(i can not find this information on the product page...?)

 

If it is like the UMO, the PWM frequency is 30 KHz, so a ~1-10 Khz low pass filter should make the fan happy. Obviously, a smaller resistor is better, but 1/RC should be about 10000 or less. The UMO supplies 19V to the fan, so I used 10 ohms to knock that down some. For a UM2, I would guess that a 1 ohm resistor would be better. With a 20 uF cap, the cut off frequency would be ~8 KHz, which ought to do the trick.

At least, that is what solved a problem when I installed a replacement fan. The symptom was that it would only run when the PWM was close to 100%.

 

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UMO is different but assuming you mean UM2...

The 2 fans are wired in series (which they are not designed to do so if you buy a different model 12V fan definitely buy them in pairs and a different fan might not work well). The 24V goes across both fans at the same time such that each gets 12V.

The 24V is pulsed on and off many times per second. When you ask for 0% fan there should be 0V across the 2 fans. 100% should be 24V across the 2 fans. When you ask for 50% the voltage pulses between 0V and 24V many times per second. Multimeters won't be able to measure the voltage accurately - you would need an oscilloscope - when it's not at 0% or 100%.

19V across one fan or both? Note that if you pull up the plastic shielding there are 2 connectors connected by a short wire. Those go to the 2 fans. Or they are supposed to. There is a 3rd fan in the back of the print head. That one gets 12V I think and is not pulsed.

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