Anyone have any thoughts on how to go about designing a fan relay for

3D Printing
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1

Anyone have any thoughts on how to go about designing a fan relay for a printrboard? I’d like to really get my cooling where it needs to be, but I’m concerned the the FET may not cope with the fans I am planning on using.

Can anyone provide me some guidance on how I might go about accomplishing this either by controller a relay from the existing fan output or using a free GPIO to control a relay? Ideally I’d like to retain the ability to control fan speed, but actually have the PWM frequency be high enough to not cause audible whine.

2

Fans only really use around 1A or lower. A fet is going to be FAR better than a relay.

3

Woah, don’t plan on a relay switching fast, much less fast enough to be above audible range.

4

https://www.sparkfun.com/products/10213 is basically what you need, but it’s way overkill. Just something with a 5v gate saturation voltage.

5

What sort of fans are you using where an on-board FET isn’t going to be enough?

6

You can use the fan output to drive a 12v relay directly.

7

@Stephanie_A , older printrboards don’t have a fan output. At least, if I’m remembering correctly. Then again - he did say he’s worried about the FET…the existing one I take it?

8

Maybe a better question is: what are you planning to use these fans on? (part cooling, hot end cooling, printrboard cooling, all of the above, something else?)

9

All models of the printrboard had/have one fan plug. RevF added a higher spec fet. Future revs are planned w two fan outputs- one got hotend, one for cooling prints.

10

@SirGeekALot , I just want to improve part cooling. While two small 40mm fans are adequate for most situations, I’ve definitely run into situations where more cooling would improve my prints. I’m thinking of running two significantly more powerful 50mm blowers, but only running them at full speed in specific situations.

@Brook_Drumm , I think the max continuous current draw that improved FET is rated for is 1.2A, is that correct? In theory I should have some headroom, but not as much as I would like to have.

11

That sounds right. The blower fans are pretty good. Our 30mm fan (Ubis 13s cooling) does 3cfm… The best I’ve seen- beats some blower fans for sure.

Did you see that article about the best cooling method? One focused fairly tightly on the print and one blowing generally across the print area? Interesting read of you can find it. Very scientific approach to the findings. He even sites modes for fan shrouds.

Do t be afraid to put a desk fan on really difficult prints either :wink:

12

I would suggest a fancontroler from a PC with the 12 volt supplyed from your powersupply .

13

@Stephanie_A I don’t run a printrboard, but the ramps 1.4. I did this esaxct thing for my heat beds. I’ve got 4 mk2 beds running off server psu that is cycled on and off via relay that is controlled by the fet of the ramps.