Weird fan issue

[antiklesys]

I bought two 30mm chinese fans that run at 12V and they are cursed/possessed/do black magic.

So the story is as it follows:

They work ok if I connect them to a PC PSU on the 12V line
They also work ok if I connect them directly to the UMO PSU (19V)
They also work ok if I connect them to the electronics fan PIN (FAN3) of the UMO.

If I place them on the head to cool the print, they don't work.
I tried replacing the transistor but that didn't make any difference.
I tried using a 24V 30mm fan to cool the print and that works ok.
I tried using a 12V 40mm fan to cool the print and that works ok too.

It is just those two 30mm 12V fan that seem to cause issue.

If I connect them manually to the wires on top of the printing head they twitch (only once) and then they just stand still for the rest of the time.

Anyone's got any clue on what's going on here?

Additional info: UMO electronics V 1.5.6

[LePaul]

Is the power for the fans running next to the heater block/sensor wiring? If those wires are close, weird things happen

[antiklesys]

It's not and I tested the wiring too with the other fans.
Also the heater block was off during the tests

[Amedee]

Can you also confirm that they don't run when the fan setting is 100% (255)?

I think your fans don't like PWM...

[antiklesys]

The way I was testing them was with FAN SPEED 100% by setting it on the ulticontroller.

[Amedee]

That's really strange indeed, at 100% you just get plain 19V.

I don't know which transistor you put back in, but if my memory serves well, the original one is a BD679 which can take 4 amps at saturation, which is more than enough for any fan...

Can you
- Check the voltage you have at 100% fan when no fan is connected (should be 19V as your other fans are working, but just to be sure)
- Same when the fan is connected

If the voltage drops when the fan is connected then the fan asks more power than the transistor can deliver, either because it is bad, not saturated or the fan needs way too much power a startup... (If you have an amp meter you could check that, but that not something everybody has...)

If the voltage doesn't drop...
... then I really don't know as you said it is running fine on the UMO PSU...

[antiklesys]

The BD679 was replaced just to ensure it wasn't messed up, but as mentioned in the first post it didn't change anything.
The voltage when no fan is connected is 19V

The voltage dropped to 13V with the fan is connected, but as far as AMPs are concerned, the fan is labelled for 0,06A (and the 24V fan is for 0,08A) so unless something's fucked up inside it, on paper it should've been ok.

Now a weirder thing happeend. I plugged in the 12V fan in parallel of the 24V fan and it started!
It started spinning and working as normal, but the 24V fan stopped spinning instead....

I'm confused.

[Amedee]

Mmmmh...

If the voltage drops to 13V, this is very bad.
I double checked the schematics and the transistor is directly connected to the PSU 19V. If the voltage drops it is because the fan drains a lot of power.
Maybe because at 19v it is out of specs... (that doesn't really explain why it works when mounted with the 19v though...)

Did you tried with both fans in series?

[antiklesys]

Tried your advice and connected them in series (the two 12V fans). None of them was moving.
I also tried to connect one 12V fan in series with a resistor, still no go.

[Amedee]

I am out of ideas here...

There is definitely something wrong with these fans, but I'm afraid that without a lab power supply it will be difficult to know exactly what.

The main issue is the UMO design where they choose to use 12V fans with a 19V PSU, so it is a challenge to find fans which at the same time support PWM and accept to be way overpowered...

For dual fan setup, I decided to go with 24V fans to avoid the overvoltage issue....

[LePaul]

How many wires do these fans have? Just positive and negative?

[antiklesys]

How many wires do these fans have? Just positive and negative?

Yes, just those two.

[LePaul]

Any progress on your fans?

[antiklesys]

Hey man, no I just gave up and purchased a few 24V ones from E3D.
Did you have any other advices or things to try?

[LePaul]

I did not but was curious how you solved the issue