fans on different voltages

VJ

@mikebridge Interesting idea, although getting a Duex2 or5 may be a bit of overkill to drive some fans...

Easy would be the solution @dc42 confirmed, especially when a buck converter can be used to get the 12V from the same 24V PSU that powers the duet (of maybe better: from an always on fan header?). I can get 4 wire models of the fans. Just still looking for confirmation that there would be no ground issues then.

Also, still curious if positioning one buck converter for each fan, between the fan header (24V) and the fan (12V) is an option. But I don't know if the PWM signal into a buck converter correctly translates to the output...?

As a last resort, and perhaps most isolated from the Duet board is the use of DC-DC SSR's, but can they be used for fans?

dc42

@vj said in fans on different voltages:

Also, still curious if positioning one buck converter for each fan, between the fan header (24V) and the fan (12V) is an option. But I don't know if the PWM signal into a buck converter correctly translates to the output...?

Do not do that with controlled fan outputs, because you may damage the fan mosfet. It's ok for always-on fan outputs.

A DC-DC SSR would work.

SupraGuy

@vj said in fans on different voltages:

Thanks! Not all fans will be 12V... (at least in the beginning)
But getting the 12V from a buck converter that converts the the 24V output of the power supply to which the Duet is connected would guarantee the common ground. Yes?

As @dc42 said, using the buck converter on the fan pins is a really bad idea. Buck converters basically have an internal switching mechanism, which will compete with the PWM on the input, and the result will be at best unpredictable, and at worst it will destroy stuff.

I have a 12V buck converter, which I'm feeding to a positive rail for my 12V fans, with the negavive going to the negative fan terminal on the Duet. I bought a couple of 24V fans which I'm still using, but I plan on moving them all over to 12V at some point, since they're a third of the cost and seem to last twice as long. I have a bunch of fan headers soldered onto breadboard so that I can jumper the negative wires wherever I want, or use the tach wires if I so choose.

VJ

Thanks for the replies!
Basically, PWM-ing a buck converter is a bad idea.

@SupraGuy
I read on the wiki about the option of feeding fans with a positive power from another source and connect the negative on the negative of the Duet for control. But somehow I would prefer more separation: most likely this comes from the fact that I'm no electrical engineer and would like to keep a situation where I understand the way it all works.

So my options are:

24V-12V buck converter on the same 24V supply as the Duet3D (or powered from an always on fan connector), pwm cable of fan to FAN-
A 12V source to power the fans (could be the same as above, or its own supply), one DC-DC SSR per fan to connect it to the fan header.

If I use the always on fan connector to provide 12V power (via the buck converter), is there no issue with current/power? Let's say to power 1-3 fans?

SupraGuy

@VJ I don't think that the DC SSR is needed. It adds complexity and possible points of failure needlessly.

My buck converter is powered from the main 24V supply. I have a supply that has multiple connections, so I'm using one set to go to the Duet, and another to go to the converter, via a 3A fuse. My 12V converter is supposed to be able to supply 5A, so this should be a more than adequate supply fuse. The advantage of using the always-on fan connector would be that it's already fused.

The arrangement that I'm using is effectively the same as your first situation, but since I have some 24V fans still in use, I can't just feed the 12V to the V_FAN pin. I'll probably do that at some point when I get around to swapping out the 2 24V fans that are in use.

VJ

@supraguy said in fans on different voltages:

@VJ I don't think that the DC SSR is needed. It adds complexity and possible points of failure needlessly.

True... I know it is overkill (negative lead or pwm cable could connect to the Duet), but it is private situation (not a professional use) so an extra point of failure is not so critical and it would make the wiring more understandable to me.

My buck converter is powered from the main 24V supply. I have a supply that has multiple connections, so I'm using one set to go to the Duet, and another to go to the converter, via a 3A fuse. My 12V converter is supposed to be able to supply 5A, so this should be a more than adequate supply fuse. The advantage of using the always-on fan connector would be that it's already fused.

True on the fuse, hadn't thought of that.

The arrangement that I'm using is effectively the same as your first situation, but since I have some 24V fans still in use, I can't just feed the 12V to the V_FAN pin. I'll probably do that at some point when I get around to swapping out the 2 24V fans that are in use.

For sure at the start I will have a 24V fan, but that may change in the future. There is still a difference in the wiring: you wrote that you put the negative lead of the fan to the negative of the Duet; I would connect the PWM cable (requires a 4 wire fan though) as dc42 confirmed would work (taking into account ground issues).

Regarding what dc42 mentioned earlier in his first post

#1 will work provided that the 12V supply has a common ground with Vin

If you use different outputs on the same powersupply, does it give the 12V supply a common ground with Vin?

SupraGuy

@vj said in fans on different voltages:

If you use different outputs on the same powersupply, does it give the 12V supply a common ground with Vin?

Yes, I will have a common ground point, since the converter doesn't isolate its output ground.

VJ

@supraguy said in fans on different voltages:

@vj said in fans on different voltages:

If you use different outputs on the same powersupply, does it give the 12V supply a common ground with Vin?

Yes, I will have a common ground point, since the converter doesn't isolate its output ground.

Good to know! Euhm... out of curiosity... the powersupply also does not isolate its different outputs?

(the more I learn, the more I think I will go with the option of a DC-DC converter connected to the fan output, and PWM fans with the PWM control cable connected to FAN- of the desired fan output; no using an SSR)

planeguy

@vj said in fans on different voltages:

@supraguy said in fans on different voltages:

@vj said in fans on different voltages:

If you use different outputs on the same powersupply, does it give the 12V supply a common ground with Vin?

Yes, I will have a common ground point, since the converter doesn't isolate its output ground.

Good to know! Euhm... out of curiosity... the powersupply also does not isolate its different outputs?

(the more I learn, the more I think I will go with the option of a DC-DC converter connected to the fan output, and PWM fans with the PWM control cable connected to FAN- of the desired fan output; no using an SSR)

Been searching this fan stuff and just wondering if this turned out as planned?

VJ

@planeguy Not sure if you still need my reply... I have not yet messed around with the fans as I has quite some delays. Just last week I started with the first test prints. I have a 24v fan and am using that at the moment. The 12v route is on my todo-list, but that rather is an upgrade to make it all more silent. No idea when I will get to that though; first I want it to print.

bberger

Sorry for pushing up this old thread, but I'm (still) not quite sure how to solve my situation and don't want to start a new thread as this fits pretty perfectly. My first instinct was to just wire the the buck converter directly between fan and duet, but as I gather this is a bad idea.

Parts I have:
1x 12V hotend fan
2x 24V part cooling fan
1x 12V always-on mainboard fan

Currently I have:
1 Buck converter directly on the PSU to supply 12V directly to my mainboard fan.

Goal:
Re-Use that buck converter to power my remaining 12V fans.

From what I could gather this is what I think I'm supposed to do:

12V Hotend-Fan (negative) in parallel to Duet Fan1(GND)
12V Hotend-Fan (positive) in parallel to Buck Out(+)
12V Mainboard-Fan (negative) to Duet Always-On-Fan(GND)
12V Mainboard-Fan (positive) to Buck Out(+)
24V fans as is (directly plug them into the duet)
Jumper on V_FAN and VIN

Is that correct? Also: Does it even make sense to wire the mainboard fan to the Duet or should I just keep it wired at the Buck Converter?

Bonus question:
When my 12V 4010 Delta fans arrive (and only have 12V fans on my Delta): I'll just plug all of the fans directly in the Duet, Power the Buck Converter from the PSU, leave out(-) disconnected and just supply the out(+) to the V_FAN pin?

Bonus Question 2:
With the mixed setup (12V hotend fan, 24V part cooling fans) I still need to set the jumper on the Smart Effector - correct? If I go all 12V the wiring on the smart effector end can stay the same as the 24V setup - correct?

Phaedrux

@bberger In your case I think it would probably be simplest to simply replace the two 24v part cooling fans with 12v options and use the buck converter to feed 12v directly into the V_fan pin to provide 12v to all the fans. Simplest option, and less prone to error.

It doesn't really answer your question but it's the only answer I can recommend.

dc42

@bberger said in fans on different voltages:

Parts I have:
1x 12V hotend fan
2x 24V part cooling fan
1x 12V always-on mainboard fan

Currently I have:
1 Buck converter directly on the PSU to supply 12V directly to my mainboard fan.

Goal:
Re-Use that buck converter to power my remaining 12V fans.

From what I could gather this is what I think I'm supposed to do:

12V Hotend-Fan (negative) in parallel to Duet Fan1(GND)

12V Hotend-Fan (positive) in parallel to Buck Out(+)

Correct.

12V Mainboard-Fan (negative) to Duet Always-On-Fan(GND)

12V Mainboard-Fan (positive) to Buck Out(+)

Yes, assuming you want the mainboard fan to be always on. Alternatively, connect the mainboard fan negative to the buck regulator negative output.

24V fans as is (directly plug them into the duet)

Jumper on V_FAN and VIN

Is that correct?

Yes.

Also: Does it even make sense to wire the mainboard fan to the Duet or should I just keep it wired at the Buck Converter?

Either will work. The important thing is that when using mixed fan voltages, the VIN jumper on the Duet must provide the highest voltage needed by any fan, which in your case is 24V.

Bonus question:
When my 12V 4010 Delta fans arrive (and only have 12V fans on my Delta): I'll just plug all of the fans directly in the Duet, Power the Buck Converter from the PSU, leave out(-) disconnected and just supply the out(+) to the V_FAN pin?

Correct.

Bonus Question 2:
With the mixed setup (12V hotend fan, 24V part cooling fans) I still need to set the jumper on the Smart Effector - correct? If I go all 12V the wiring on the smart effector end can stay the same as the 24V setup - correct?

The jumper on the Smart Effector must be set according to the voltage you are supplying to the hot end fan. This is because the LEDs on it are connected in parallel with the hot end fan.

bberger

@dc42 thank you very much for taking the time to thoroughly answer my question!

One last thing though: are the 'always on' fans actually always on or can those be toggled (on/off)? Not sure if 'always on' stands for "not PWMable" or if it's actually meant literally. Couldn't seem to find any information about it, but I also may be overwhelmed by the amount of docs and source code I've read over the past few days..

@bberger said in fans on different voltages:

are the 'always on' fans actually always on or can those be toggled (on/off)?

they are directly connected to the chosen supply, no pwm, no on/off.

bberger

Sorry for reopening this again - however with the Revo Micro and it's 5V heatsink fan coming up - is that 5V fan okay to use with the provided buck converter from the HF output on the Smart Effector?

Skimming through this thread again - I'd say no - correct?

What are my options?
(apart from finding a (probably impossible to source) 12V/24V 20x20 fan with enough CFM and pressure..)

Do I need to run the full length of 1m wire directly to my Duet Wifi?

May we get lucky and just stick a standard V6 30mm duct with a 30mm fan on it..?