Cooling the GRBLshield v3 (Inventables Full/Premium #2)

JimHung
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Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by JimHung » Wed Sep 05, 2012 12:01 am

Hey all,

I noticed my GRBLshield was running hot on the last few test runs I've made - I haven't witnessed any of the artifacts or missed steps some have through overheating, but I realize it's probably a good idea to start thinking about a cooling solution if I've going to run my machine for any length of time.

To that end, I'm thinking of adding these heatsinks: https://www.sparkfun.com/products/10746 to the drivers, and rigging this fan to move the air over the board: https://www.sparkfun.com/products/9649

My questions are: Are these likely to provide sufficient cooling to the GRBLshield? Also, will connecting the fan to the 5v supply on the Arduino be sufficient to power it?

Thanks,

Jim
Shapeoko #: 564

makerwill
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Re: Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by makerwill » Wed Sep 05, 2012 1:19 am

I was looking at the same fan today. The thing I noticed from the description "... with an operating voltage of 5V, and is rated at 360mA." was it is rated at 360mA. The Arduino connected to the USB port might be supplying about 500mA which doesn't leave much current left to work with. With those thoughts, I was thinking of getting the smaller version https://www.sparkfun.com/products/9648 that is rated for 190mA.

The other option was to use a 12V version of the fan but if I move up to a 24V power supply, I figure I'll have to change fans too.

Basically, I'm curious about connecting one of those 5V fans myself and definitely would like hearing what others think about this too. :)

Update:
I forgot to mention for the heatsink, I got these: https://www.synthetos.com/webstore/inde ... s-kit.html

T4b
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Re: Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by T4b » Wed Sep 05, 2012 10:18 am

After the first few letters of the Hello world thingy from the wiki the three "DRV8811" chips got so hot that I burned my finger on one of them (it still hurts now, at least 10 minutes later).
I hope I haven't damaged them yet. They still appeared to be working right when I stopped the job and plugged everything out.

To power a 24V fan I could probably just wire it parallel to the grblshield to the grlbshield's (24V) power supply, couldn't I?
(I think it's probably a stupid question, but I'm a beginner so I want to make sure...)
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aldenhart
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Re: Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by aldenhart » Wed Sep 05, 2012 12:18 pm

The driver chips will get hot, but that's not a problem unless they go into thermal shutdown - which you will know. The first thing to do is to adjust the current. One of the main reasons for running hot is sourcing too much current to the motors. Beyond a reasonable set point they don't need it, and they get hot too. So first, adjust the current to a good set point that balances power with heat (see the grblshield wiki if you bneed instructions) http://www.synthetos.com/wiki/index.php ... or_Current

Next, fan cooling is much more effective than adding heatsinks (but heatsinks don't hurt). A little air goes a long way. Most 12v fans will not run from 24v. The ones I have experimented with do not get damaged, they just stop working. I would like to try running 2 (identical) fans in series from 24 volts, but haven't yet. This may be a solution. Another solution is to run a 5v or 12v fan from a garden variety wall wart. I know it's another PS and wires to mess with, but it's a simple solution.

- Alden

jsbannis
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Re: Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by jsbannis » Wed Sep 05, 2012 3:06 pm

My analog-circuit-foo is awful (computer science / CE background, every idiot can count to 1 kinda stuff ;)) but I think you should be able to scale down to 5 or 12 volts from your 24 with just a zener diode and a resistor.

Warning: Literally everything I know about zener diodes comes from this short article :) http://www.evilmadscientist.com/2012/ba ... er-diodes/
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Will Winder
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Re: Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by Will Winder » Wed Sep 05, 2012 3:20 pm

I must have gotten lucky with the 12v fan I am using. I've had it mounted on my stepper shield and connected to the 24v power supply for several weeks now. When I power on the electronics the little fan sounds like it is trying to take flight, but so far it hasn't.
ShapeOko #367: Dual-Y drive, Belt on outside, 1000mm Y-Axis, DW660 Spindle, Nema-23 X/Y motors.

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aldenhart
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Re: Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by aldenhart » Wed Sep 05, 2012 4:14 pm

@ jsbannis: The zener will allow you to make a crude voltage regulator. You'll need a big zener and it's going to get hot. If you want to that route (active electronics) it's easier to just get a 7812 voltage regulator that can handle 24 input (I like the ones from On Semi), or perhaps use the Zener + regulator circuit in the EMS link if you want to drop the voltage to the regulator.

@ Will - lucky guy! Can you tell us what fan you are using?

Will Winder
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Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by Will Winder » Thu Sep 06, 2012 12:38 pm

aldenhart wrote:@ Will - lucky guy! Can you tell us what fan you are using?
The fan was salvaged out of an old video card along with a heatsink. The fan and heatsink were then stuck to the top of my custom stepper shield heatsink.

The fan is a "colorful" EC-4510 rated for .08A @ 12v.

PS: Thanks to taking these pictures I found that the mounting screws warped my arduino causing one of the drivers to short!!
ImageUploadedByTapatalk1346934879.509733.jpg
ImageUploadedByTapatalk1346934879.509733.jpg (188.85 KiB) Viewed 4974 times
ImageUploadedByTapatalk1346934975.928129.jpg
ImageUploadedByTapatalk1346934975.928129.jpg (200.79 KiB) Viewed 4974 times
ShapeOko #367: Dual-Y drive, Belt on outside, 1000mm Y-Axis, DW660 Spindle, Nema-23 X/Y motors.

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JimHung
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Re: Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by JimHung » Thu Sep 06, 2012 8:34 pm

Thanks for the replies guys!

@makerwill - I too was looking at the smaller Sparkfun fan (https://www.sparkfun.com/products/9648). It appears that it has a current draw of 200mA, which as far as I can tell is (just) within tolerance for USB connections for I/O pins on the Arduino. Since I was simply planning to connect it straight to a 5v pin, I think I should be ok to run the fan straight off the Arduino over USB. It seems there is anecdotal evidence that running the Arduino off a DC supply will solve any current issues if you have any, up to any (ironically) thermal tolerance limit with the Arduino board (although this may even only apply to using I/O pins).

@Will Winder - Interesting solution - looks like you bolted an aluminium heat exchanger to your driver board and then popped the heatsink & fan on top of that? I'm almost tempted to have a dig around in our office's e-waste bin and see if there are any old heatsink/fan assemblies I can recycle..

On another note, I've been playing with testing the tolerances of my newly built ShapeOko (thread here) - the pattern runs for so long (17 minutes) that it has worked like a bit of a "burn-in" test of my electronics - turns out I start getting overheating artifacts at about the 7 minute mark. Those out there with Arduino/GRBLShield v3 stacks and NO cooling solution - how long can you run your machine for before seeing overheating problems (if ever)?

Cheers,

Jim
Shapeoko #: 564

cvoinescu
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Re: Cooling the GRBLshield v3 (Inventables Full/Premium #2)

Post by cvoinescu » Thu Sep 06, 2012 11:26 pm

Will, as far as I know, a lot of the cooling of the driver chips occurs through the PCB (they have pads specially designed to transfer heat into the PCB), so you may get better results if you blow air on the board directly, without any heatsink, than if you cool a heatsink in contact with the tops of the chips. I'm not 100% sure, of course, but I'm not the only one who says this. Small individual heatsinks on the chips that don't block the airflow around the PCB can only help, but the PCB itself is the path of least thermal resistance to the chip.
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