Did I break the fans?

drmaestro

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

A Former User

@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

A Former User

@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.

Phaedrux

Those would probably work to allow you to manually control the fan speed while using the always on connector.

A simple latching switch could work too.