Layer Fan Woes

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thingismith
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Layer Fan Woes

Postby thingismith » Sat Nov 04, 2017 10:22 pm

For the longest time I didn't bother with setting up the layer fans because I just didn't need them. Lately I decided to set it up, but I'm having issues. When I first set it up, the accelerometer was hooked up and the led light told me it was getting power, but alas, no fan movement :x . I know the led light is for the layer fans because I was turning it off and on in my machine control.

I decided to try hooking up the fan directly to the duet, still nothing (shorted my first fan control in the process :cry: ). Measuring the other two, 7mA and 8mA. Just 1 of my fans need 90mA (I've got 3).

Does this sound right? Should I be getting more power to my layer fans? Is this something I need to fix in the config? I have the fans turned up to 100%.

dc42
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Re: Layer Fan Woes

Postby dc42 » Tue Nov 07, 2017 3:27 pm

If you shorted out an always-on fan connector, you may have fused the PCB trace that feeds power to the fans. Remove the fan voltage selection jumper and check continuity between the centre pin of that jumper block and the + pin of the VIN terminal block or the bed heater terminal block. If there is no continuity, you can add a wire on the back of the Duet to bypass the trace.

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thingismith
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Re: Layer Fan Woes

Postby thingismith » Tue Nov 07, 2017 11:15 pm

Thanks for the reply dc42. I checked for continuity... There's none between the middle pin and the + of the blocks, but there is on the right pin.... the diagram I found http://reprap.org/mediawiki/images/thumb/7/7b/DuetWifi_connectionsv1.0.png/640px-DuetWifi_connectionsv1.0.png says the Vin is the right one.

I should mention that the always-on fan connections do work, with both my duetwifi cooling fan (which is normally connected) and my squirrel fan.

Any other suggestions?

dc42
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Re: Layer Fan Woes

Postby dc42 » Wed Nov 08, 2017 2:46 pm

You are right, it's the VIN side of the jumper block that should be connected to VIN. But if the always-on fans work with the jumper in the VIN position, it's OK anyway.

Fan 1 defaults to thermostatic mode, so to control it normally you need to send M106 P1 H-1. Other than that, if you are only getting a few mA out of the fan outputs when you command them fully on, then it sounds like the fan mosfets have blown due to overload.

Does your fan use a brushed DC motor? Normal fans are brushless, but the motors used in water pumps are normally brushed. If it does use a brushed motor, and you have a version 1.0 or 1.01 Duet, then you need to add a flyback diode to protect the mosfets from the back emf of the motor.

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thingismith
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Re: Layer Fan Woes

Postby thingismith » Fri Nov 10, 2017 12:55 am

Sorry, I should have mentioned that I have a duetwifi in the beginning, and I do have brushless fans.

I entered M106 P1 I0 S1.0 B0.1 H-1 (varying with P2 and P3), still no dice.

I only have an intermediate (self-taught) understanding of electronics, how could I have blown the mosfets? By shorting them out? I know I shorted the 1st fan, and am getting no amp reading at all. Shouldn't I be getting the same 0 amp readings for the other 2? I have no idea how I could have blown all 3 of them, I haven't even touched them until recently.

There are 3 sets of jumper pins below the fan connectors, 2 have jumpers on them, but not the one on the far right. I couldn't find any literature on it, is it supposed to have a jumper on it?

If I can't figure this out soon, I'm just going to throw my hands up in the air... I need to get back to printing!

dc42
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Re: Layer Fan Woes

Postby dc42 » Fri Nov 10, 2017 4:31 pm

thingismith wrote:Sorry, I should have mentioned that I have a duetwifi in the beginning, and I do have brushless fans.

I entered M106 P1 I0 S1.0 B0.1 H-1 (varying with P2 and P3), still no dice.

I only have an intermediate (self-taught) understanding of electronics, how could I have blown the mosfets? By shorting them out? I know I shorted the 1st fan, and am getting no amp reading at all. Shouldn't I be getting the same 0 amp readings for the other 2? I have no idea how I could have blown all 3 of them, I haven't even touched them until recently.

There are 3 sets of jumper pins below the fan connectors, 2 have jumpers on them, but not the one on the far right. I couldn't find any literature on it, is it supposed to have a jumper on it?

If I can't figure this out soon, I'm just going to throw my hands up in the air... I need to get back to printing!

Connecting a brushless fan with the wrong polarity can also blow both the fan and the mosfet, it depends on the fan. So if you wired the red and black wires the wrong way round and tried each fan connector in turn, you could have blown more than one. Last time I wired a fan the wrong way round, the fan blew but the Duet fan output survived.

If you are in the US, one option for you is to send a PM to forum user W3DRK on the Duet3D forum. He provides a Duet repair service, so he could give you a price for replacing all three fan MOSFETs if that is what's needed.

I am assuming you do not have any M106 commands with parameter I-1 in config.g, because those commands disable the corresponding fan.

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thingismith
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Re: Layer Fan Woes

Postby thingismith » Sun Dec 03, 2017 7:52 pm

So I took your advice and sent my Duetwifi to W3DRK. Apparently you were right, it was the Mosfets. He offered to do it for a reasonable price, fixed it quickly, and always returned my messages immediately. I just got it back and now it works like new. Thank you dc42 and W3DRK!


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