Berd-Air pump configuration notes for Duet users

dc42

@hergonoway said in Berd-Air pump configuration notes for Duet users:

@msquared

Just set F25500 and it damn quiet now thanks for the tip.

But adding a thermistor (the ref given by DC42) in series doesn't work at all, at least for Berdair 24v pump.

I guess that pump doesn't draw enough current to heat the thermistor up. There is probably another thermistor in a smaller size that would work. I'll order a few different types and test them.

Hergonoway

@dc42

thanks for your help ! unfortunately my multimeter is broken, I can't give additional feedback for the moment.

coredump

So, did anyone try the high frequency PWM with a module like this?

In my test here, using F500 and keeping the pump running at 30-40% gave me a lot of air, and not a lot of noise (I am using this on both intake and outtake), but the F25000 took away my ability to control the pump speed and sounds a little higher. I haven't tested temperatures yet with the two different F values.

I wonder if I should try to connect the pump directly to the DuetWifi. If there's not a lot to gain from that change in the noise department, I think keeping the module makes it safer.

BenDiesel

Have you cracked one of the mufflers open to see how it works?

coredump

@bendiesel unfortunately they are all one piece injected plastic, so it's not trivial to open.

They definitely lower the noise tho.

Responding my own question: that mosfet module that I added definitely blocks the high frequency PWM trick. I took a chance and connected the 24v pump I got from markerhive and connected it directly to my duet wifi (1.02) and with the highfrequency PWM I can run it at 20-30% with minimal noise.

Lets see how many fan ports I burn on this tho

coredump

This post is deleted!

coredump

@hurzhurz said in Berd-Air pump configuration notes for Duet users:

@msquared About the flayback diode, your link points to a 1N4007.
I have first tried this one, but it got pretty hot.
After some googling I think the reason is that the diode is just too slow for a high frequency of 25kHz (reverse recovery time of 30us).
I have replaced it by a schottky diode that doesn't get warm.

Are you using a 1N4148 or something different?

hurzhurz

@coredump
I'm now using a MBR345 as this was the first schottky diode I got into my hands after I read that schottkys are probably more suitable for higher frequencies.

And by the way, I have reduced the frequency to 20kHz so the mosfet stays a bit cooler.

fma

About the noise your are talking about, is it the PWM frequency you can ear, and so it disappear at 20kHz, or is it something else?

ShadowX

@hurzhurz

Schottky rectifiers are more suitable for low voltage applications. Its not always the best choice because its prone to thermal runaway if its not heat sinked properly. The reverse leakage increases exponentially with temperature so it needs to be designed properly for thermal dissipation.

The preferred diode is a fast rectifier with a low forward and recovery time. There are many different types available. There SMD and also leaded parts so it depends on your application.

https://www.allaboutcircuits.com/technical-articles/fast-ultrafast-soft-standard-schottky-selecting-the-right-rectifier/

Chipsa82

Hi

Im thinking of using the Berd Air concept from components I have laying around - what is the OD/ID of the metal pipe? is it stainless? thanks!

Hergonoway

@chipsa82

Standard tubing used by berdair are 3/32" OD aluminium tube.

I've personnaly switch to soft brass tube of 1/8" OD (Wall: .014") from K&S. Used a wire in the tube to bend it (honestly it's almost mandatory for larger tube) and solder the end instead of pinched it.

I don't recommend stainless tube if you want to make a tube ring with 12mm ID, because it already not so easy with softer material.

If you go over 3/32" it "may" require makerbot type nozzle which has 8mm clearance compare to 5mm clearance from E3D nozzle type, mostly for convenience especially if you use a headblock sock.

c310

@dc42 said in Berd-Air pump configuration notes for Duet users:

I guess that pump doesn't draw enough current to heat the thermistor up. There is probably another thermistor in a smaller size that would work. I'll order a few different types and test them.

did you have a chance to test other thermistors ?
what will be your final recommendation for DuetWiFi board 1.03+ ?
should i add any electronic components or i can safely directly connect the 24v pump to fan output of the duet board?

thanks!

dc42

I'm sorry, I haven't tested other thermistors yet.

If the DC resistance of the 24V air pump is less than about 7 ohms then you should use either a surge-suppression thermistor (or other surge reduction device) in series with it, or an external mosfet switch that can handle the surge current. You could try a 7 ohm resistor in series, but that may get rather hot and also limit the pump speed.