Need Advice on Maestro Fans Max Current

CCS86

Hi guys,

I am currently running my Maestro with a print head fan, a hot end fan, and a fan to cool the mainboard.

Now I am adding a beefy auxiliary fan. Does the 1.5A max apply if you are connecting a fan directly to a power supply (24v) and then grounding through the fan pin for PWM control?

If so, how can I control a fan that exceeds this? Is there some sort of relay I can use, or does PWM complicate it.

Phaedrux

I think you're ok if you're supply the voltage from a separate power supply directly rather than the voltage pin on the fan header.

CCS86

@Phaedrux said in Need Advice on Maestro Fans Max Current:

I think you're ok if you're supply the voltage from a separate power supply directly rather than the voltage pin on the fan header.

Okay, that's promising. Maybe I'm not a complete moron.

That was my first thought too... since I'm just running the ground through the Maestro for PWM, I thought the current limit didn't apply.

Then, I hooked it up and powered on. My old config had a thermostatic control for my control board fan in place, so the new fan fired up full speed for a second or two, then throttled back and ran for maybe 5 more seconds at various speeds. Then I thought l smelled magic smoke and cut power.

The fan was supposed to be rated at 1.6A / 24V according to the spec sheet (https://www.digikey.com/en/products/detail/delta-electronics/BFB1224GH-A/5799881). But after this moment of panic, I looked at the fan itself and it says 1.9A.

Maybe it is just new fan smell, but I had already hooked it right to the power supply for a full speed blast and didn't notice the smell. Not sure if PWM control can cause more of a smell with a new fan.

So, hopefully I can get some solid confirmation of whether externally powered fans must abide the current limit before I try again, and pray I didn't smoke fan control on my poor little discontinued Maestro.

dc42

@CCS86 yes the 1.5A limit applies to the fan outputs even if you use separate power. It's limited by heating of the fan mosfet.

Are you already using the second extruder heater output? If not then you could use that to drive the fan.

CCS86

@dc42 said in Need Advice on Maestro Fans Max Current:

@CCS86 yes the 1.5A limit applies to the fan outputs even if you use separate power. It's limited by heating of the fan mosfet.

Are you already using the second extruder heater output? If not then you could use that to drive the fan.

Okay, that explains the smell! Hopefully, I shut down before it got ruined.

I am not using the second extruder output, so that is great news. Is there a write up anywhere about doing that, or is it as simple as a normal fan definition and using the pin from the extruder output?

In case I did damage something is there anything I might miss by changing from my Maestro to a Duet 3 Mini 5+?

T3P3Tony

@CCS86 said in Need Advice on Maestro Fans Max Current:

I am not using the second extruder output, so that is great news. Is there a write up anywhere about doing that, or is it as simple as a normal fan definition and using the pin from the extruder output?

Yes define the fan using the pin name for the second extruder heater.

CCS86

Okay, it does look like I cooked the FAN2 mosfet. Bummer.

what would be the recommended PWM frequency for a big blower like this? It is electronically pretty loud, even throttled back.

CCS86

Oh man, you've got to be kidding me.

I was playing with different PWM frequencies and kicking the fan on at around 35% to check noise.

It seemed better at 100 Hz, so I tried 50. It just buzzed and didn't spin, so I kicked it off after maybe 1 second. Now it won't run at the higher frequencies. I got a

VIN under-voltage event (9.5V)

When I just last tried to turn it on.

Did I smoke this fan???

dc42

@CCS86 looks like your fan may have developed a short circuit, or else you have the positive and negative wires crossed.

CCS86

@dc42 said in Need Advice on Maestro Fans Max Current:

@CCS86 looks like your fan may have developed a short circuit, or else you have the positive and negative wires crossed.

I definitely have the polarity right.

You can't think of any reason that a low PWM frequency would cause this? It was running nicely on the heater circuit until I changed PWM to 50Hz.

Now it won't turn when hooked directly to the 24V supply.

When I check resistance across the wires, it is ~1.5 k-ohm

dc42

@CCS86 2-wire fans are not designed to work with PWM. It's a minor miracle that so many of them do.