Duet 3 mini move breakout points further away from heatsinks
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In my (1.0) revision of the PCB of the duet 3 mini 5+ the breakout points for step/dia and other are very close to the heat sink part for the stepper drivers. When mounting an extra heatsink I need to take care not to place it on the breakout points to prevent shorts (I am using thermal glue, not thermal pads), and I can also only use small heatsinks.
Placing the breakout points farther away reduces the risk of shorts and makes sure that any heatsink mounted sits flush on the pcb (notice the solder on some of the breakout points in the attached pic)
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@nikscha duet boards are designed to not require heatsinks
if any cooling is required, blowing air across the back of the board with a fan is sufficient -
@jay_s_uk yes I know that.
I used to run the duet 2 wifi which can handle more current on the steppers (2.5A peak vs 2A, mine was set to 1.8A)
Using the same config for my duet 3 mini caused several 'over temp' warnings and ultimately aborted the print. Pointing my thermal camera at the drivers reveals they were at 105c degrees!
Reducing the stepper current to 1.4A lowered the temps to 70c but now I get missed steps (granted I have pretty aggressive acceleration).I also cooled my duet 2 wifi with heatsinks and usually had temps at around 40c degrees, rarely getting above 50c.
It seems like if I want to push the drivers and run my steppers at the same current as before I will need heatsinks.
Just because the duet or the drivers are rated for high temps doesn't mean it's healthy. Thermal expansion and thermal degradation are a thing and I bet the caps don't like high temps either. Sure, big heatsinks might be overkill but moving the breakout points a few mm back really shouldn't be an issue
Stay in school
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@nikscha Another problem is that the duet 3 mini has no on-board temp sensor, the steppers only set flags for warning and overtemp. That means I need to always run the enclosure fan, not only when the drivers get hot.
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@nikscha
Comparing the duet3 mini with duet2 isn't fair. You should see it as upgrade of the Maestro.1.8A from a TMC2209 is a challenge. Better go for watercooling, there's also no problem with the breakout-points.
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@o_lampe fair, but the alternative is 160 euros more expensive and wayyyy overkill for my application.
I also really don't see why it would be a problem to move the breakout points away by a few mm. There's definitely enough space on the ground plane and it makes cooling the board easier.
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@nikscha You can use something called Kapton tape and tape over those testpoints before you put your heatsinks on and they will be well insulated from any issues.
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@alankilian thank you for the suggestion
