heatsink?

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  • March 14, 2011 at 10:11 am #1743
    mmcp42
    Member

    If I’m driving 3 steppers at 2.5A will the board need any sort of cooling or heat sinks?
    What do you reccommend?

    Also – what are shipping costs to UK likely to be?

    cheers
    Mike

    March 16, 2011 at 3:49 pm #1744
    alden
    Member

    Mike, you will find most of you answers on the wiki.
    https://www.synthetos.com/wiki/index.php?title=Projects:grblShield

    See here: and look for cooling.
    https://www.synthetos.com/wiki/index.php?title=Using_the_grblShield

    We ship USPS flat rate internationally, so I think that’s about $12. If you place an order or at least take the shopping cart that far it should tell you the exact amount. – Alden

    July 4, 2011 at 1:26 am #1745
    HadleyRille
    Member

    I have a similar question. I’m going to try to drive three 1.4A motors, and expect that it’s going to generate some heat. I have read the cooling section on the page linked above.

    I saw the images of the massive heatsink for the mini-g that attaches to the bottom of the board. It looks like I could machine a modest heatsink that could attach to the bottom of the board in the space between the Arduino and the grblshield. I could make a bigger heatsink by standing up the grblshield with a set of shield stacking headers. I could make a pretty big heatsink that contacts the driver cases on the top of the board where there is lots of space, but i imagine heat transfer through the epoxy case won’t be as good as if the sink was on the bottom. Whatever I end up with, it’s easy enough to mount a fan to keep air moving over it.

    What do you recommend?

    Thanks!
    -John

    July 5, 2011 at 7:59 am #1746
    alden
    Member

    John, You should have no problem with 1.4A motors – I have driven much larger with and without heatsinks. We are putting some heatsinks on the site soon. We found some copper heatsinks used for RAM cooling by case modders. These work pretty well.

    We also looked at underside mounted solutions, but there’s not much room between the boards – especially with the ISP programming header sticking up off the Arduino.

    If you have any issues with heat you will know it – as the driver chips will cycle on and off due to thermal shutdown – or even stutter in extreme cases. In most cases this means you have your current set too high and are overdriving the motors. Back it off until the stuttering stops, then check your torque. You should still have plenty. The chips may run hot, but this is expected.

    The most effective cooling is to use a fan. Blow some air across the board and through the gap between the Arduino and the board. This actually makes much more difference than any heatsinks we’ve tried – including the monster on the TInyG board. However, at 1.4 amps you should not need this.

    Also (ironically) the motors run cooler with higher voltages as the power electronics spend less time in switching. So running at 24v will provide better motor operation and cooler chips than running at 12v.

    Alden

    July 6, 2011 at 10:36 am #1747
    HadleyRille
    Member

    Thank you. I should have my motors in a week or so and will report back.

    July 10, 2011 at 1:59 am #1748
    HadleyRille
    Member

    Got my motors. They’re actually 1.7A/phase. They are very torquey and run smoothly. I’m running them from a 20v power supply, but intend to switch to a 27v 11A supply soon. I haven’t run them for a long time yet, maybe 40 second runs. The chips get warm, but aren’t shutting down, and this is with no cooling at all. Looking good.

    July 10, 2011 at 8:41 pm #1749
    Riley
    Keymaster

    These TI chips are pretty nice. And with all the extra copper that alden added to the PCB… It really makes the board pretty tough.

    Riley

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