Passive cooling

uk25 · 16 Jun 2016, 13:44

I dont want use any additional fans for cooling the board with so quiet stepper drivers. So i decided take a normal-size heatsinks and install them on the board.

On the picture bellow i marked the elements which in my opinion needs to be cooled:

But i want to ask about other hot elements of the board which i must cover by the heatsinks too?

dc42 · 16 Jun 2016, 14:12

The main processor doesn't run hot so no cooling needed there. The WiFi module also only runs warm.

Putting heatsinks on top of the driver chips won't help much if at all, because the chips are cooled through the PCB - in fact they may make things worse by restricting airflow over the PCB.

If you want to use passive cooling, the best option is to mount the Duet vertically, and make sure that air is free to circulate over both sides of the PCB naturally by convection. An alternative if you need to mount the Duet horizontally is to use a large slow-running (and therefore quiet) fan, which you could mount below the Duet and spaced about 10mm or more from it. If you go this route then I suggest an Arctic F12 PWM fan or similar, because in future we may provide thermostatic control of electronics cooling fans based on CPU temperature. Bear in mind that most PC fans need 12V, so you will need a voltage regulator if you will be using 24V power.

The other area of the board that may get warm is the bed heater mosfet and surrounding PCB area, below and to the right of the bed heater terminals

Aussiephil · 16 Jun 2016, 14:28

I'm going down the road for this and the 0.8.5 of using 75mm blower fan that are actually nearly silent but still move enough air… still working on the custom enclosure that directs the airflow over the bottom of the board, fans are not always noisy

uk25 · 16 Jun 2016, 15:28

@dc42:

The main processor doesn't run hot so no cooling needed there. The WiFi module also only runs warm.

Putting heatsinks on top of the driver chips won't help much if at all, because the chips are cooled through the PCB - in fact they may make things worse by restricting airflow over the PCB.

If you want to use passive cooling, the best option is to mount the Duet vertically, and make sure that air is free to circulate over both sides of the PCB naturally by convection. An alternative if you need to mount the Duet horizontally is to use a large slow-running (and therefore quiet) fan, which you could mount below the Duet and spaced about 10mm or more from it. If you go this route then I suggest an Arctic F12 PWM fan or similar, because in future we may provide thermostatic control of electronics cooling fans based on CPU temperature. Bear in mind that most PC fans need 12V, so you will need a voltage regulator if you will be using 24V power.

The other area of the board that may get warm is the bed heater mosfet and surrounding PCB area, below and to the right of the bed heater terminals

I understood that heatsinks are practically useless, and the better way for my setup still use a fan but the most quiet… something like 120mm Noctua above the board.

.

@Aussiephil:

I'm going down the road for this and the 0.8.5 of using 75mm blower fan that are actually nearly silent but still move enough air… still working on the custom enclosure that directs the airflow over the bottom of the board, fans are not always noisy

can you tell the model of your fan?

T3P3Tony · 16 Jun 2016, 21:47

While a fan is probably more effective if you want to try a heat-sink for the stepper drivers then mounting one on the bottom, under the drivers, with some good thermal grease would be the way to go. The area under each stepper driver has 4 sections which act as heat sinks as well as connecting t the header pins:

Getting a good thermal connection across all 4 tracks to a heat sink might be enough.

We are going to be conducting thermal testing at some point next week and after I publish the results you should have a better idea of what needs to be done for your application.

Cheers

Tony

Aussiephil · 16 Jun 2016, 23:25

Hi Uv..

the fans i bought were from here http://www.ebay.com.au/itm/321865191866?_trksid=p2057872.m2749.l2649&var=510809488962&ssPageName=STRK%3AMEBIDX%3AIT

they certainly live up to the ultra low noise at the expense of being able to force lots of air but the flow from one of these will be good for board cooling.
I have no air flow measurement tools but the blow it in your face test, these seemed to have the same air flow volume as a smaller noisy blower (50x20 i think)

Cheers

uk25 · 17 Jun 2016, 08:14

Thanks all of you for your answers!
Let's wait thermal testing from Tony.

deckingman · 19 Jun 2016, 10:27

If you are looking for quiet fans, I've always found this to be a good place to look https://www.quietpc.com/casefans. Even if you don't buy from them, it's a good source for information on airflows, noise etc.

uk25 · 20 Jun 2016, 07:44

@deckingman:

If you are looking for quiet fans, I've always found this to be a good place to look https://www.quietpc.com/casefans. Even if you don't buy from them, it's a good source for information on airflows, noise etc.

Thanks! I use this site for a long time. Last time I found on it a quiet nice Gelid Solutions Silent 4 for my previous kossel build.