My LimeSDR is dropping frames

[g4guo]

My first thoughts are to use the aluminium case that goes with the @luftek end plates.
Then to buy some aluminium square bar cut to the right length and add thermal foam pads to
one end of each (the end that will press against the chip). The other end of the bar will be bolted
to the case.

When the case is closed the bars/pads will gently push against the main chips taking the heat out to the case.
I can then add a standard large heatsink to the outside of the case and a thermally controlled fan like those
mentioned by @Zack .

I really don’t like the idea of blowing air over the board as what ever you do it will accumulate a layer
of sticky dust which will act like a thermal blanket.

• Charles

[hTo137]

[quote=“g4guo, post:21, topic:881, full:true”]
When the case is closed the bars/pads will gently push against the main chips taking the heat out to the case.
I can then add a standard large heatsink to the outside of the case and a thermally controlled fan like those [/quote]

The pad idea is interesting. I don’t know how much pressure these parts can take and alignment might be tricky.

I really don’t like the idea of blowing air over the board as what ever you do it will accumulate a layer of sticky dust which will act like a thermal blanket.

This is true and with so many small parts the potential for problems goes up as dust, etc. accumulates.

[hTo137]

Sounds right that it’s heat. Do you have a way to read the temps besides finger test? I ask only because it would be interesting to generate a heat profile for these. I have to find my infrared thermometer and do that.

[9a4db]

Therefore my solution blowing only internal air / disipating the heat on box walls
and second heatsink with fan is outside on the box top.

[g4guo]

This is the method Red Pitaya use in their diecast case.
I found some 2 mm thick thermal pad on eBay (usually used for GPUs etc).
The centres of the main chips on the Lime are inline so it shouldn’t be too difficult
to drill the holes. You can get 10 mm and 20 mm square Aluminium bar on eBay.

The biggest problem will be cutting the square bar flat and to the right length.
I can always put a washer in there made out of copper sheet if I over do the cut.

You can get copper sheet of various thickness’s (again on eBay).
I even found some heatsinks the same dimensions as the case.

Worth a try anyway.

• Charles

[hTo137]

Interesting that one of those parts is listed as “Active” and they have 0 stock and the other is listed as “Last Time Buy” for 2017-12-31 and they have ~12,000 with EOL announced on July 2016.

FWIW I am going to use a slow fan that just recirculates air internally and one like these mounted externally.

[hTo137]

@leoha if you’re curious about the power usage here’s a good synopsis:
I wonder if anyone has a USB3 power doctor to check the real numbers.

Power consumption

Short answer: The upper limit is 4.5 Watts (Maximum that USB 3.0 can supply). But the power required will be less than ~ 3.082 Watts. Since the FM demodulation is most likely going to be executing on the host computer, I do not think it would matter much what demodulation was being used. What would matter is the data rate, so if the data rate was low then I’m sure things could be in a lower power configuration than the maximum I describe below. But there would be a lower limit, which would be 1…

[hTo137]

I too have concluded this is the simplest approach. Additionally I plan to use a large case with heatsinks adhered/mounted on the inside of the case walls as well as heatsinks on each of the chips.

FYI, for the external fan/heatsink, I read a lab report that found that drawing/pulling air over the heatsink performs better than pushing air into the heatsink. IIRC most CPU coolers draw/pull air.