Did I break the fans?

drmaestro

Hi,

I have 2 part cooling fans which were wired together to form a single lead, which was connected to PWM fan input on the board. The wiring (the splitting) was a little bir problematic and it was disconnected today. While I was trying to repair the wire, I probably shorted the positive and negative wires together. Now, I can't turn the fans on. If I set the fans to 100% and measure the voltage on the unconnected wire I read around 12 volts, so I assume the connection at the borad side and the PWM circuit is not damaged. However, when I connect the fan to the cable the voltage drops to 1-2 volts and there is no movement except small milimetric shakings. Did I damage the fans (or the board)?

Thanks...

Probably damaged the mosfet driving the fans. You could verify the fans working by moving them to a always on fan header set to the appropriate voltage.

drmaestro

@bearer Would it be possible to repair it? Maybe I can use another PWM connector (the other 2 are free).

bondus

It can be repaired, you can swap out the broken mosfet component. Some SMD soldering skills required.
But as you say there are two more to ~~burn~~ use. M106 configures the fans in RRF2 (and some M950 in RRF3)

dc42

@drmaestro said in Did I break the fans?:

Hi,

I have 2 part cooling fans which were wired together to form a single lead, which was connected to PWM fan input on the board. The wiring (the splitting) was a little bir problematic and it was disconnected today. While I was trying to repair the wire, I probably shorted the positive and negative wires together. Now, I can't turn the fans on. If I set the fans to 100% and measure the voltage on the unconnected wire I read around 12 volts, so I assume the connection at the borad side and the PWM circuit is not damaged. However, when I connect the fan to the cable the voltage drops to 1-2 volts and there is no movement except small milimetric shakings. Did I damage the fans (or the board)?

Is it all the fans that won't turn on, or just the one you shorted?

Which Duet is it?

drmaestro

Hi,

If I connect the fan to the always on connector on the Duet (WiFi), the fans turn on, so I can confirm that the fans are working. Then, if I remove the connector and connect it to PWM connectors (1,2 or 3) and then use the screen to turn the fan to 100 (full power), nothing moves. I also tried m106 P0 s254, m106 P1 s254, and m106P2 s254 commands but still, nothing moves. Do I need to make some change to the m106 commands at the config files before giving these commands?

Thanks.

Phaedrux

@drmaestro said in Did I break the fans?:

Do I need to make some change to the m106 commands at the config files before giving these commands?

The commands in config.g would be pretty much the same, so no.

Are you using RRF2 or RRF3? If using 3, you'd need to have some M950 commands in config.g to create the fan pins before M106 can address them. In RRF2 the fan pins are pre-defined.

That all said, it really does sound like you've damaged the fan mosfets.

drmaestro

@Phaedrux I am on RRF2. Is it possible to damage all three mosfets at the same time, even though 2 of them weren't connected to any fans and the non PWM fans are working?

dc42

@drmaestro said in Did I break the fans?:

@Phaedrux I am on RRF2. Is it possible to damage all three mosfets at the same time, even though 2 of them weren't connected to any fans and the non PWM fans are working?

No, only the one that had the output shorted is likely to have been damaged.

Fan 1 is configured in thermostatic mode by default, so you would need to disable thermostatic mode before you can control it manually.

drmaestro

@dc42 Here are the relevant sections on my config file:

M563 P0 D0 H1 F1; Define tool 0 (I added the F1 to be able to assign the second PWM fan to my hotend)

M106 P1 S0 I0 F500 H-1 ; Set fan 1 value, PWM signal inversion and frequency. (Thermostatic control is turned off by using H-1 and removing the T command)

Am I doing anything wrong on the config part?

Phaedrux

@drmaestro I think that looks ok.

After that's been set, can you turn on the fan with M106 S1?

drmaestro

@Phaedrux Nothing happens. Is there a way to test the problem using a multimeter?

@drmaestro said in Did I break the fans?:

@Phaedrux Nothing happens. Is there a way to test the problem using a multimeter?

sure, you could probe the mostfets with the diode junction function. you could measure the voltage at the gate to confirm its getting a signal from the processor.

https://www.google.com/search?q=mosfet+multimeter+test

droftarts

@drmaestro Long shot; does your Duet have a fan fuse (Duet 2 Wifi/Ethernet v1.03 and later)? Have you checked it?

But does sound like the MOSFET has failed.

Ian

drmaestro

@bearer What should the voltage be when m106 S1 command is given?

drmaestro

@droftarts It doesn't have a fan fuse, it is an earlier Duet WiFi (1.02 maybe) which also didn't have the fuse for the heated bed (I had to solder a fuse to the board when the smd component burned 2-3 years ago).

drmaestro

Also, is it normal that I am reading 12.4 volts at the fan wire (measured from the Dupont connector side) when the fan is set to 0 and the fan is not connected but if I connect the fan the voltage drops to 1.2 volts?

droftarts

@drmaestro MOSFETS switch on the ground (or negative) side, so you will always read 12V (if VIN is 12V and the V_FAN JUMPER SELECT is on the VIN and V_FAN pins) on the positive pin. The voltage drop is probably explained by a failed MOSFET, but you really need to check it with a multimeter as @bearer suggested.

My Duet Wifi daily-driver is a pre-production white PCB version; no fuses and some of the pins are a different way around! Haven't managed to kill it yet...

Ian

@drmaestro said in Did I break the fans?:

@bearer What should the voltage be when m106 S1 command is given?

I'd test without power and according to the google search link, far too much to repeat in a post here.

if not, you should have close to 3.3v on the gate when the fan is on, and Vin on the source pin of the mosfet.

drmaestro

I've had an idea today about the fan and would like to ask your opinion on the subject. Until I can fix the board, I was thinking of a temporary solution, which is to connect the part cooling fan to the always on connector. That way, I can cool the part. I understand that the slicing software can vary the amount of cooling depending on the contents of the layer, so this isn't an ideal solution but it is better than not having part cooling for PLA prints. The only problem is how to turn it off for the first 3-4 layers, so that the part can stick to the bed. Right now, I am pausing the print at the 4th layer ans disconnecting the fan connector at the hotend but I am not very comfortable leaving unconnected wires around the hotend. I've found some fan controllers at Aliexpress (for example https://www.aliexpress.com/item/32983495011.html?spm=a2g0o.productlist.0.0.165062189TcZdL&algo_pvid=46d10c0f-61a5-4856-ba09-ca38e93a022d&algo_expid=46d10c0f-61a5-4856-ba09-ca38e93a022d-0&btsid=0ab6d70515864703710462983e2ec8&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_) . Would it be advisable to use them?

Thanks.