Confused about fan voltage.

fcwilt

@blaidd

Which fan pin are you measuring?

One of them is tied to Vin and is always present if the power supply is on.

The other is switched to ground to control speed.

Unless you set the min speed setting in M106 the min setting is 0.1 or roughly 10%.

The 2.0 v you are measuring is likely due to that.

To test, in the M106 command where you create the fan add the parameter L0 to specify a min setting of 0.

Frederick

Blaidd

@fcwilt I freely admit I don't know a whole lot about electronics, so perhaps I'm doing this wrong? I didn't even think you could measure a single pin. This is what I've been doing: I have one of those digital multimeters with a red wire and a black wire, and you can turn the dial to select what you want to measure. I set the dial to V200 (V20 gives me an error, presumably because it's above 20), then I touch the red probe where the red wire goes, and the black probe where the black wire goes. I did this on the pins themselves, and on the tiny bit of exposed metal on the connectors (the ones I'm using to connect the fan to the DB15 wire are similar to the ones that come with the Duet for connecting to the board in that you clamp a metal piece onto the wire, then shove it into the plug, and the place where it has a little piece that clicks in to lock it leaves a tiny bit of the metal showing).

I added the L0 you mentioned to the end of my M106 line, and with the fans plugged in I got the same result as before: 2.0 volts regardless of whether it's set to 0%, 100%, or anywhere in between. The change comes when I unplug the fans. Then it registers 24.0 volts at all times, instead of the 20.4 it was registering before, again regardless of whether I have it set to 0%, 100%, or anything in between.

fcwilt

@blaidd

So you are measuring the 2 volts with the fan connected and you are measuring across the two terminals the fan wires are connected to?

Does the fan speed vary with the speed settings?

Frederick

Phaedrux

@blaidd said in Confused about fan voltage.:

I have two (24 volt) 5015 blowers, each red wire and each black wire are connected together so there's a single 2-way plug.

Photos?

The PWM fan headers switch the negative side, so you can't share the negative wires for 2 separate fans. You can share the positive wires though.

If you connect the blower directly to the fan0/fan1/fan2 headers you should be able to configure them and control them with

M950 F0 C"fan1" Q500
M106 P0 S1 H-1

That should turn fan0 on full.

Blaidd

@fcwilt

@fcwilt said in Confused about fan voltage.:

@blaidd

So you are measuring the 2 volts with the fan connected and you are measuring across the two terminals the fan wires are connected to?

Exactly. 2.0 volts if the blower is plugged in, 20.4 (now 24) volts if the blower is not plugged in.

Does the fan speed vary with the speed settings?

Frederick

The blower fan does not come on at all, no matter how I adjust the speed or the config settings, that is the problem.

@phaedrux said in Confused about fan voltage.:

The PWM fan headers switch the negative side, so you can't share the negative wires for 2 separate fans. You can share the positive wires though.

That's what's confusing me. It was working that way several months ago. I had the two different blower fans, with the two red wires twisted together and put together into the one hole of the plug, and the two black wires twisted together and put together into the second hole. Now, I can't get it to work, but I didn't make any changes, other than not using them for several months. I'll try to take some pictures later.

Phaedrux

So it sounds like you've wired the two blowers together to a single header in parallel. What are the specs of the blowers? It's possible you've blown the fan mosfet.

https://duet3d.dozuki.com/Wiki/Connector_and_spare_part_numbers#Section_Fan_mosfet

Check the photo in that link and compare to your board.

Blaidd

@phaedrux

I currently have the main part taken apart, but here's the quick connect plug I mentioned.

And here is the board itself, which is in a difficult position because I built an enclosure and attached it underneath, but I don't see anything that looks melted or blown.

If there's anything you want me to zoom in on, or if you need me to temporarily pull off the duex board for my thermistor so you can see the board underneath, let me know. If you need to see the bottom of the board, I can do that too but it's going to take a bit of work to get it out.

Blaidd

@phaedrux Oh, and these are the blowers I used. I'm not sure which specs you're looking for, but hopefully it'll be on that page: https://www.amazon.com/gp/product/B0755BY9RH/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Phaedrux

If you connect the blower directly to the fan0/fan1/fan2 headers you should be able to configure them and control them with

M950 F0 C"fan1" Q500
M106 P0 S1 H-1

That should turn fan0 on full.

Have you tried that yet? Fan directly connected to the header with no additional wiring?

The fan mosfets are very small little chips near the fan headers. Get a close up well lit of the fan header area.

Blaidd

@phaedrux Even with a single blower fan plugged directly into the board, it still does not work.

Blaidd

@phaedrux Well, crap. I finally managed to take a really good picture of the area, and I'm thinking you're right, the mosfets do seem to have that black spot.

Phaedrux

d97775ba-46ae-4465-be86-16036ec994e5-1626754679050-img_20210719_211602531.jpg 1626754679050-img_20210719_211602531.jpg

Those two mosfet chips look like they have holes blown in them just like in the example from this link.
https://duet3d.dozuki.com/Wiki/Connector_and_spare_part_numbers#Section_Fan_mosfet

They can be replaced, but they are very small chips with 3 legs. Will depend on how handy you are with an iron. A cell phone repair shop or other electronics repair place might be able to do it. Or a local maker space?

Blaidd

I decided to replace the whole board, since I believe I short circuited something when I was doing the testing. I also broke at least one of the plastic "tongue" things, and possibly a pin, when I was doing all the plugging in and unplugging.

@phaedrux said in Confused about fan voltage.:

@blaidd said in Confused about fan voltage.:

I have two (24 volt) 5015 blowers, each red wire and each black wire are connected together so there's a single 2-way plug.

The PWM fan headers switch the negative side, so you can't share the negative wires for 2 separate fans. You can share the positive wires though.

I did have the two negative wires (and the two positive wires) connected so I could run the two blowers in parallel (one on left side, and one on right side). IMG_20210722_140841300[7085].jpg

It worked for a while, but I want to be sure to do it right with the new board. I noticed when I was setting up my dual Z axis there was a way to connect them to two different pins but control them with a single command from the slicer:

M584 X0 Y1 Z2:4 E3
M574 Z1 S1 P"zstop+e1stop"

Is there any way to do the same thing with the blower fans? For example, instead of twisting the wires together, plug them individually into Fan0 and Fan1 slots, and do something like:

M950 F0 C"fan0" Q500
M950 F1 C"fan1" Q500
M563 P0 D0 H1 F0:1

For what it's worth, I intend to update the new board to the newest FW and just copy the config.g (etc) files over.

cosmowave

@blaidd Your connector can lead to a problem!
You should try to crimp them more carefully. The free thin copper wires can produce a short circuit!

DIY-O-Sphere

@blaidd said in Confused about fan voltage.:

M563 P0 D0 H1 F0:1

You got it...
Exactly like in the example...
https://duet3d.dozuki.com/Wiki/Gcode#Section_M563_Define_or_remove_a_tool

Blaidd

@diy-o-sphere Thanks. That helps a lot more than the only thing I had found about it, which was here: https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans and didn't include anything about adding more than one of anything.