Hello All I see many comments re attaching a heatsink to the microchip actually doing the work on the pololu breakout boards to prevent the chip burning out. I was wondering what one uses for this. I have found various adverts eg. thermal paste on ebay but am not sure this will work as required... will it resist the vibration the machine may produce... is it neccesary to use something else to keep the heatsink in place with this paste just providing thermal conductivity or is the paste a glue as well? Thanks for any advice. https://reprap.org/forum/read.php?13,67280,67280#msg-67280 Thu, 11 Jun 2026 10:12:02 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?13,67280,68339#msg-68339 https://reprap.org/forum/read.php?13,67280,68339#msg-68339
I think i was probably unsuccessfully trying to point out that while normally, as an "approach" one would set the driver board around the motor and application (e.g. for a 2,5-3,5A chips to use with a 1-1,5A motors ofc max current isnt the objective), on pololu boards the max current is probably so low anyway, that just setting for max current could be the way to go.

As a sidenote, at some point doing some research into why 3.3 stepper driver has ct470pf instead of 680pf (datasheet) or 1000pf (more common over the net in designs i found on a3977), i runned into some datasheet that was supposed to double check the fet values and currents for a3986 (this was somewhat a much debated chip over cnc-zone at that time), and i found it to be fairly nice approach over an 3 sheet xls file for a motor math and its currents - is here [www.c-n-c.cz] I even played with it a little wanting to get something similar for a3977 math -bar fets which are internal- for better documentation on it, but got both stuck on some areas and confused on others, and couldnt find my way out. Keeps bugging me tho, and would love to see something like that still for a3977, as i pretty much got to like this chip so far although its not all that new, but to me it feels somehow solid. Sorry if i jump from one thing to another or if my comments are somewhat messed up, half of my brain is always wandering somewhere else all the time and most of the times i cant even say which side is missing :)]]> NoobMan Controllers Mon, 13 Dec 2010 20:47:39 -0500 https://reprap.org/forum/read.php?13,67280,68328#msg-68328 https://reprap.org/forum/read.php?13,67280,68328#msg-68328 Triffid_Hunter Controllers Mon, 13 Dec 2010 17:56:15 -0500 https://reprap.org/forum/read.php?13,67280,68280#msg-68280 https://reprap.org/forum/read.php?13,67280,68280#msg-68280
I avoided setting the max current because with overkill heatsinks and a3977 allowing slightly bigger max currents, the motors were kinda much too hot to my appreciation, so i positioned myself relative to that aspect alone. For myself i just roughly appreciated half current - half torque thingy out of like ~0.4Nm to get half current and ~0.20Nm (as specified "needed"), and further than that i only cared for motors heating up - as i had no issues with anything else. My own impression was that the actual required torque must be a little less than the 0.20 anyway and the motors should run without issues.

I think pololu drivers have their real max current kinda lower, maybe up to ~1A (or maybe 0.5~0.7 rms just a guess, no real clue - but there was a thread on it). Therefore a good setting is probably significantly closer to their top currents, so you end up aiming for max current anyway. And then ofc the chip heat is more of an issue than it is for other boards/chips.]]> NoobMan Controllers Mon, 13 Dec 2010 08:39:58 -0500 https://reprap.org/forum/read.php?13,67280,68274#msg-68274 https://reprap.org/forum/read.php?13,67280,68274#msg-68274
I am not sure what current I am using but I wind it up until either the chips or the motors are just too hot to touch. I want the torque as high as possible to make the motors stiff and minimise backlash and overshoot rather than the minimum.]]> nophead Controllers Mon, 13 Dec 2010 05:50:27 -0500 https://reprap.org/forum/read.php?13,67280,68270#msg-68270 https://reprap.org/forum/read.php?13,67280,68270#msg-68270 The point is to run the motors with the lowest current possible, to avoid motors getting too hot. As a result of that, the driver chips wont heat up much either.

I have 12 pololu driver boards but never used any, not even so much as for testing - yet.
Instead, i use the stepper driver board 3.3v with a 3977 and like 3.5-4 cm heatsinks. I have some 1,2A and 1,5A rated motors with like 0.35-0.4Nm torque, i ran them at approx 0.5-0.7A current and that seems to give enough torque so all movements are quite ok, the chips heatsinks are always cold (radiators are at room temp full time while running), and motors are like always "touchable" like 45-50 degrees or so - i guess.

You will need to find the lowest current settings where the motors are happy and give just enough torque, then you will find out what will be needed. To do that, you need to adjust it with the full mechanical setup - to be able to test stepper movements. You will need to start with a very low current setting and go up only if its actually needed. Good luck.]]> NoobMan Controllers Mon, 13 Dec 2010 04:33:12 -0500 https://reprap.org/forum/read.php?13,67280,67979#msg-67979 https://reprap.org/forum/read.php?13,67280,67979#msg-67979 -------------------------------------------------------
> I just bought some video ram heatsinks... complete
> with sticker on the bottom... I cut the heatsink
> into 4... then peel and stick.
>
> Al...

Hey Al

Have you found the heatsinks alone to be sufficient or do you need to blow air over them as well?

Thanks]]> AgeingHippy Controllers Thu, 09 Dec 2010 08:11:06 -0500 https://reprap.org/forum/read.php?13,67280,67375#msg-67375 https://reprap.org/forum/read.php?13,67280,67375#msg-67375 Triffid_Hunter Controllers Wed, 01 Dec 2010 20:16:58 -0500 https://reprap.org/forum/read.php?13,67280,67338#msg-67338 https://reprap.org/forum/read.php?13,67280,67338#msg-67338
I tried 2 types of thermal epoxy, but both were very expensive and messy (2 components that you have to mix at the right ratio) and they never really stuck that well. I've had very good results with the superglue trick.]]> Matthew Controllers Wed, 01 Dec 2010 09:29:08 -0500 https://reprap.org/forum/read.php?13,67280,67332#msg-67332 https://reprap.org/forum/read.php?13,67280,67332#msg-67332 this heat sink glue from DX for a while with great results. What it may lack in thermal conductivity it makes up for in strength. I believe you can also get it in smaller tubes from the same site if you don't need quite as much

As always keep in mind the very long shipping times from DX which will only get worse towards xmas.]]> Capo Controllers Wed, 01 Dec 2010 08:11:09 -0500 https://reprap.org/forum/read.php?13,67280,67324#msg-67324 https://reprap.org/forum/read.php?13,67280,67324#msg-67324
Al...]]> araspitfire Controllers Wed, 01 Dec 2010 05:14:05 -0500 https://reprap.org/forum/read.php?13,67280,67297#msg-67297 https://reprap.org/forum/read.php?13,67280,67297#msg-67297
I use these for many things including Reprap electronics - and they fit perfectly on GEN3 steppers, they are self adhesive (tape) - http://www.kustompcs.co.uk/acatalog/info_2877.html

9mm ones are also available, they should fit on Pololu.

You could use Aluminium ones, they cost less and do a good enough job -
http://www.kustompcs.co.uk/acatalog/info_2833.html

Rich]]> richrap Controllers Tue, 30 Nov 2010 17:22:20 -0500 https://reprap.org/forum/read.php?13,67280,67292#msg-67292 https://reprap.org/forum/read.php?13,67280,67292#msg-67292 hydraraptor.blogspot.com]. I haven't tried it yet.]]> nophead Controllers Tue, 30 Nov 2010 15:25:27 -0500 https://reprap.org/forum/read.php?13,67280,67291#msg-67291 https://reprap.org/forum/read.php?13,67280,67291#msg-67291
Thanks Nop]]> AgeingHippy Controllers Tue, 30 Nov 2010 15:02:25 -0500 https://reprap.org/forum/read.php?13,67280,67287#msg-67287 https://reprap.org/forum/read.php?13,67280,67287#msg-67287 www.aria.co.uk]]]> nophead Controllers Tue, 30 Nov 2010 14:27:11 -0500 https://reprap.org/forum/read.php?13,67280,67280#msg-67280 https://reprap.org/forum/read.php?13,67280,67280#msg-67280
I see many comments re attaching a heatsink to the microchip actually doing the work on the pololu breakout boards to prevent the chip burning out.

I was wondering what one uses for this. I have found various adverts eg. thermal paste on ebay but am not sure this will work as required... will it resist the vibration the machine may produce... is it neccesary to use something else to keep the heatsink in place with this paste just providing thermal conductivity or is the paste a glue as well?

Thanks for any advice.]]> AgeingHippy Controllers Tue, 30 Nov 2010 13:04:31 -0500