cooling and more memory?

Any technical questions about the Epiphany chip and Parallella HW Platform.

Moderator: aolofsson

Re: cooling and more memory?

Postby AlbertoGP » Sat Jun 07, 2014 7:57 pm

timpart wrote:Rather late I've just spotted an issue. Don't use anything conductive that could short TP13 at 1.0 Volts to TP12 and TP14 at ground.

Thanks! Just this morning I tried with yet another heatsink, just for the ZINQ this time, and had a metal clip ready to go between TP13 and TP14 but I wasn't sure so I left it out. I'll keep the plastic one as before.


This one fits exactly. There are some small caps at the north-west quadrant so I taped the underside of the heatsink there.
zinq-heatsink-top.jpg (89.95 KiB) Viewed 11299 times

zinq-heatsink-general-view.jpg (84.61 KiB) Viewed 11299 times
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Re: cooling and more memory?

Postby timpart » Sat Jun 07, 2014 11:27 pm

aolofsson wrote:Can you send the link to the old schematic. I thought we had purged all old copies.

Sorry should have made that clearer. I had two versions on my hard drive. For some reason I didn't move one from my downloads directory. I hadn't realized it had been updated since, as they don't get announced and I don't download the schematic very often.

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Re: cooling and more memory?

Postby svartalf » Wed Jun 11, 2014 3:30 am

AlbertoGP wrote:However, the Zynq is supposed to get even hotter: would it be counterproductive to put a common bigger heatsink over both chips?
Would that transfer extra heat to the Epiphany?

Better late than never in reply, I guess.

Short answer is YES and you don't want to do that. Heat flows through the path of least resistance. If they're pretty even on dissipation, it'd be "fine"- but if there's a major difference between the heat sources, at least part of the heat from the hotter running device will get dumped into the "cooler" device until the heat sink evens out. (Lessons learned up at work...basically, it's a "Doc, it hurts when I do this," sort of thing... :twisted:)
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Re: cooling and more memory?

Postby svartalf » Wed Jun 11, 2014 3:35 am

As it stands, I'm going to look into a smallish fan and blow it over two differing heatsinks. I've got the one in the box that Adapteva thoughtfully provided, which may/may not be adhered by way of the tape on it or Artic Alumina- and I've got a bevy of RAM heatsinks I bought on eBay a while back for re-doing the thermal management on my Equiso HDMI sticks so they're stable. It should handle the Ephiphany decently enough. A low airflow mini-fan should quietly fix the thermals. Now...thinking on how to do this without boogering up my nifty case TOO much. :twisted:
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Re: cooling and more memory?

Postby AlbertoGP » Wed Jun 11, 2014 5:56 pm

Yes, it's just like Andreas said a few times: the big factor is whether you have a fan or not.

The nicest fitting of the fan to the case I've seen is by bszente in the thread "does the board contains thermal sensor(s) ?".

That's what I wanted to do now that I've given up on passive cooling, but where I'm now I don't have a drill big enough for a hole that size and I'm worried about botching it. I rather like the acrylic case; it has a couple of small shortcomings but I've found it to be very flexible and well thought out.

What I've done instead is make a metal bracket to hold two 30x30x6mm fans in place of one of the long sides:
fan-clip-before-and-after.jpg (59.55 KiB) Viewed 11231 times

fan-clip-inside.jpg (61.57 KiB) Viewed 11231 times

The bends at the left and right extremes need some adjustment but it clips nicely in place already.
fan-clip-outside.jpg (53.74 KiB) Viewed 11231 times

That's too much but I want to see what happens. To maximise the airflow I leave the opposite long side off and the top lid on.
The power source is a solid 3A and I'm running the headless configuration so there is enough power for those two fans. They are the 30mm variant of the 25mm mentioned in other threads; the whole catalog is here: Sunon DC Brushless
The smaller variant would be better because it's quieter, and with the metal bracket I have a vibration and resonance problem so I'll try things like removing one and adding dampening. Right now it sounds like a small server, but those guys do bring down the temperature a few more degrees than the 92mm 12v running at 5v I've used until now.
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Re: cooling and more memory?

Postby AlbertoGP » Thu Jun 12, 2014 1:51 pm

Adding a rubber strip between the fans and a tight rubber band around them reduces the resonance but they still make quite a lot of noise. These fans are just too loud for this use.

The best result I can report is the following super-simple and effective rubber band mount for the fan:
I wish I had thought of this earlier.
rubber-mount.jpg (43.35 KiB) Viewed 11208 times

The band is a slice from a mountain bike tire; quick to make and fit, and very adjustable: sliding the band on the plastic mount points up or down changes the tension on each side of the band, the tighter side pushes the fan in the opposite direction, and you can then adjust the vertical position to the millimeter.

It also holds fans of different thicknesses, so instead of 6mm it could be a more common 10mm or even 15mm. A deeper tunnel makes the fan more efficient and I think you could get the same amount of airflow with a slower-spinning and therefore quieter fan.
You could use a 12V fan at 5V like Dr.BeauWebber did in the thread Another simple fan for the Adapteva case. For that you need to check the starting voltage of the fan: it varies from model to model, I've seen some with 8, 6, or 4.5V of starting voltage. One that needs more than 5V will not start, or if it is close enough it might spin once you push it but then if it stops for whatever reason it would not start again on its own and your board would fry.
For the Sunon fans, you can find that information in the extended specification PDF from here:
Select some parameters, for instance size 30x30x10 and voltage 12, then in the result table you have the PDF link at the right side for each model.

Using one fan instead of two the temperature goes up 3 degrees.
In both cases, having the opposite long side of the case in place means around 2 degrees more.

-- Alberto
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Re: cooling and more memory?

Postby AlbertoGP » Wed Jul 02, 2014 7:06 pm

I've tried different fans, all from Sunon, and here is the result:
MC25060V2: 25x25x6mm at 5V, the initial one mentioned by Adapteva, is small, pushes a good amount of air but makes some annoying noise.
MC30060V2: 30x30x6mm version of the above, pushes more air but is noticeably louder, way too much for me.
MC30101V2: 30x30x10mm 12V running at 5V, very quiet (can't hear it from 1.5m away, but it's not a completely quiet room) and pushes a bit less air than the above but not by much. More than enough to keep the board at a good temperature.
HA30101V3: 30x30x10mm 12V running at 5V, it's a slower speed version of the above meant to be quieter, but when running at 5V the very low noise feels the same for me as the other while pushing noticeably less air.

These are the A99 variants (e.g. MC30101V2-000U-A99) which have two wires; the G99 variant is just the same with a third wire that reports the RPM measurement: it costs more (~2€) so it only makes sense if you can't find the A99 version of the fan you want.

The 6mm thick fans fit inside the case, although you would have to cut a circle in the side panel to allow air to flow ("does the board contains thermal sensor(s) ?"), while the 10mm ones require either a square hole or replacing the panel entirely as I did.

V nominal is the standard voltage for the other measurements (airflow, noise, RPM, etc.), V start is the minimum it needs to start spinning on its own, mA is the current in milli-Ampères, RPM is Revolutions Per Minute, CFM is Cubic Feet per Minute: the airflow it pushes if there are no obstacles (to deal with obstacles, look for "static pressure"), dB is the noise in decibels at the nominal voltage.

V nominalV startmARPMCFMdBSpecs

My recommendation for anyone that wants to mount the fan on the side is to use a fan similar to either the MC25060V2 for compactness, or the MC30101V2 for quietness. I've picked the MC30101V2 with the rubber band mount I mentioned before and I'm very happy with it.

Top-mounted fans are less constrained for size and you can see some examples in the thread Show your Parallella!.
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