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reh191

Installation of second fan went wrong (UM1) - Need Help

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Hello guys,

I need your help. I'm not very well versed in electronics.

I wanted to install a second fan on the right side of the printhead of my Ultimaker1. I bought the fan (50x50x10 mm, 12 V, 0.09 A) and a y-cable on ebay for connecting both fans to the same pin, that one for the printhead fan.

I thought this should be no problem to have both fans in a parallel circuit. And it worked very well, while printing the fanduct for the right fan (fan was connected, but not mounted on the printhead). After that, I assembled everything completely and I was going to print a Ultibot to check the print quality, when my printer shut down suddenly at half of the print. A strange smell diffused and announced the disaster. I was afraid that I blew up my electronics.

Nothing happend when turning the power switch on and off. Not yet sure why, but after a while my Ultimaker was working again in an other plug socket.

Now the strange thing is that the left fan is always working and always on full speed. I can't control it with the UltiController nor the gcode regulates it while printing.

Meanwhile I identified that the bad smell was caused by the right fan, which had a shortcut or was overheating or something else (I don't know).

Has anybody an idea how to get my UM working properly again (in the best case with two fans) or how to identify what's wrong?

I'm deeply grateful for every tip!

Thank you in advance,

Eddie

 

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Since your original fan is now running all the time it sounds to me like you blew the transistor (or is it a mosfet? I'll have to check if no on else jumps in) for the fan due to the short in the new fan. You'll have to replace that and make sure that your new fan, and connection, is correct to try again.

 

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I exported these from Eagle if they help Jonny.

ultimakerBoard

ultimakerSch

 

edit again: Screw it, I can't be arsed to fix the image. It's already taken 30 minutes of my life (had to re-upload 6 times because the uploader kept hanging. I then changed resolution, which looked fine on my end, but was messed up on the forum end... *sigh*).

 

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If the print header fan connector is the one just right of center on the top of the 1st picture IRobertI posted then Q4 is the one that probably needs to be replaced. It is just below the top, more right of center mounting hole.

It's a transistor, BD679 (the one previously linked) so it's orientation matters. Before removing the existing one, determine it's orientation. Usually they differ from front to back so find the same front or back indicator and ensure the orientation is correct. For example, front is probably the one with the markings on it or has a dimple on it.

They are cheap so buy two in case you get the orientation wrong and the magic smoke escapes.

You will need to be able to solder it back in. You will need solder wick to clear the holes after removing the dead one. The easiest way to remove it is (FIRST NOTE THE ORIENTATION) use flush cutters to clip the leads and remove the "head" if possible. Then heat each remaining lead and remove one by one. Then use the solder wick to suck the solder out of the holes. Place the new on in the correct orientation and solder.

 

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So I looked at the specs for the transistor and it seems like it should handle two fans without a problem.

On issue might be that the fan is supplied with the full 19V from the power supply. Most fans are 5V or 12V so this higher voltage might cause a problem.

Do you know what voltage the fan is designed for?

 

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That is a darlington transistor. It is already operating near it's limit. When the transistor is fully on it is quite happy as all the energy is going to the fan. When it is off there is definitely no problem either. But when it is switching between on state to off state, if the fan is inductive, it can generate thousands of volts potentially which can blow up the transistor. It's the same circuit for making sparks for a spark plug in a car. There should maybe be a flyback diode.

However from your failure mode I think the fan failed first and that caused the failure to the transistors.

Q4 breaks quite commonly and it has two fault states - always on, or always off.

You might also want to know that the Marlin firmware has two different pulse modes for this fan: fast and slow. Slow mode supposedly is less likely to damage Q4 but fast mode is less likely to interfere with the temp sensor or something like that. You have to choose which mode when you compile and create a version of marlin. I think the versions that come with Cura are 'slow" mode.

 

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@johnnyB, please grab the latest eagle software - it's free so next time you will have this at your fingertips...

Where to get circuit diagram:

ULTIMAKER1

The circuit diagram, and board layout are here:

http://reprap.org/wi...er's_v1.5.7_PCB

There is a zip file at the top. It contains the "brd" file which is the layout. Also the "sch" file which is the schematic.

Both files can be opened by eagle software which is free:

http://www.cadsoftus...download-eagle/

ULTIMAKER 2 SCHEMATIC

https://github.com/U...aker/Ultimaker2

 

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So I looked at the specs for the transistor and it seems like it should handle two fans without a problem.

On issue might be that the fan is supplied with the full 19V from the power supply. Most fans are 5V or 12V so this higher voltage might cause a problem.

Do you know what voltage the fan is designed for?

 

As I wrote before, the fan I bought has 0.09 A and 12 V and the original Ultimaker fan has 0.10 A and 12 V.

 

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It looks like the print head fan that is used in the UM1 is 12VDC 1.2W so that would imply that it draws 100ma at 12 volts. Probably higher at 19V but I doubt that it is more than 200ma. The transistor can handle 4 amps or 4000ma. So two fans shouldn't be a problem.

However, if the fan load is inductive, it might cause high enough voltage spikes to kill the transistor.

I would check the Y cable for shorts and check the voltage rating of the fan.

It's possible the high voltage killed the new fan causing it to fail shorted and that caused the death of the transistor. Of the high spikes from the fan caused the death of the transistor.

Definitely should have a flyback diode on it....

 

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I barely know enough to make recommendations so take this with a grain of salt...

You might add two diodes such as a 1N5400 just at the end of the Y cable that for each fan across each connection. Just don't get the polarity wrong. Then shrink wrap them. I believe that the line in the diode would connect to the plus side and the other side to the - lead.

Anyway, that is what I would try....

However, I blew up my stepper drivers last night so it's important to consider that I don't know what I'm doing....

 

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The fan actually does run from 19V (probably PWM'd down to 12V RMS maximum because a 12V fan shouldn't survive 19V for long).

If you add two fans on the same transistor, then you also double up the inductive load on the transistor, which is what probably blew up your transistor.

Adding a freewheeling diode (something like a 1N4001 would do fine) should help. You might just end up blowing up the replacement transistor as well if you don't add one.

 

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In case you are wondering, this is what we are discussing:

http://en.wikipedia.org/wiki/Flyback_diode

When the flyback diode is used to simply dissipate the inductive energy, as with a solenoid or motor, cheap 1N4001 and 1N5400 series diodes are used instead.

I recommended the 1N5400 because its higher current capacity but I'm not sure how to size a flyback diode. I think I read it should handle the current that is seen in the coil. So in this case, that would be something higher than 100ma x 2.

 

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It's actually 12V, not 19V. I just checked the schematic one more time. The voltage is lowered from 19V to 12V at IC1. The 12V signal is called vcc/2 for some reason. Why don't they just call it 12V? Anyway that is the signal that goes to the fan. The other side of the fan goes to the darlington transistor which grounds the fan when you want to turn it on.

The flyback diode is a great idea. I'm thinking maybe there is already one built into the first fan. You certainly don't need two flyback diodes as one will take care of both fans. You could put the flyback diode on either fan or on anywhere in the fan circuit.

This post has too many errors. It's 19V and there is already a flyback diode as mentioned in the next post.

 

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NO DIODE NEEDED!

I just looked at the BD679 part and it has a flyback diode built into it. So no need for this. I should have guessed this in the first place!

The people who designed this board (rep rap people originally?) knew what they were doing. The switch for the nozzle heater also has a flyback diode but in that case it's a separate part. That's what got my thinking about the fan.

 

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Ahh yes the datasheet shows an internal flyback.

However, are you sure about the 12v? VCC/2 is coming directly from the power switch and is connected to pin 1 of the regulator which I believe is the VI (voltage in), VO is pin 3 and is the 12 V going to powering the auduino.

The transistor has a max current of 4A which is quite a lot for these two fans. If the flyback is integrated, why is it so easily killed?

 

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19V to a 12V fan might kill a lesser quality fan and if it fails shorted, it will also kill that transistor.

I'd would recommend that if you connect a second fan after replacing the transistor, reduce the maximum to 50% -70%...

I was wondering how that little fan produced so my air. Its overvolted...

I noticed that the electronics cooling fan is a 24v fan...

 

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And what about using a 24V fan...? (respectively two 24V fans each 0.095A) so overvolting cannot happen

Let me summarize: If I understand you right, I just have to replace that transistor Q4, check my connections for shortcuts, replace the broken fan and I don't need an additional flyback diode. Is that correct?

And by the way: Thank you all for the awesome help!!

 

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Oops - yeah it is 19V. You definitely don't need a flyback diode. You should purchase a fan that can handle 19V. I guess that 12V fan you bought can't handle it.

 

I just have to replace that transistor Q4, check my connections for shortcuts, replace the broken fan and I don't need an additional flyback diode. Is that correct?

 

Yes. I'm sure you don't have any shorts yet. The only short was probably from the new fan which didn't take the 19V very well.

 

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Yeah, forget about the flyback diode....

The issue with using a 24v fan is it will run slower at 19V.

Ideally, If you could get another fan that is the same make and model of the one on the UM1, you might be able to support two at 12V overvolted to 19V and really get some air blowing.

a 24V fan (or two) might still work even running slower since obviously there will be more fans blowing.

Not sure what to recommend you do..

 

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19V to a 12V fan might kill a lesser quality fan and if it fails shorted, it will also kill that transistor.

...

 

This has nothing to do with quality. If the product is specified to run at 12V DC (plus minus something of course), then running it at 19V DC is simply running it out of it's specifications and thereby "probably going to damage the product".

It may or may not work, but it's definetly unwise to do that.

The voltage specifiaction of a transistor doesn't have anything to do with quality either. Lower voltage transistors usually have a lower On-state resistance (higher current capability, better efficiency) than their higher voltage pendants...

Instead of using 24V fans you could also connect two 12V fans in series. That's almost as unprofessional as running a 12V fan on 19V, but it should work if the two fans are the same model and there won't be any danger of damaging the fans.

By the way, my 12V Noiseblocker fan also works on the UM1 at 19V. Usually at 100% fan speed. But I have already noticed deteriorating performance. I'd guess this comes from the high ambient temperature around the fan, but it may also be that the fan's electronics overheat from the 19V supply voltage...

 

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Hey fellows,

I'm back with a progress report. You've helped me a lot. I soldered a new transistor on the conductor board. Even with my limited soldering skills, I have been successful and my fan (original one, overvolted) is working properly again.

Now I'm designing fan ducts for the two new fans. When I'm finished and I've mounted both fans, I will report my progress.

Big thanks to all of you!!

 

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