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Flagbit
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My 2 Cents: Coin Heatsink :)_

Wed Mar 23, 2016 3:45 pm

Lowers Temperature Peaks at Overclocked SOC.
IMG_20160323_163313small.jpg
My 2 Cents Heatsink
IMG_20160323_163313small.jpg (57.25 KiB) Viewed 11143 times
e.g. from 75°C to 62°C at a short openssl speed test @1275Mhz
e.g. from ??°C to 65°C at a short openssl speed test @1350Mhz (overvolted)
(Glued with a loctite glue normaly used for screws)

edit:
A 10, 20 or 50 eurocent coin applied with two sided thermal tape should work much more better because of more copper % and should be easy to remove.
Also there are aluminium heatsinks with thermal tape already applied available for around one euro.

edited:
openssl test:

Code: Select all

openssl speed rsa4096 -multi $(grep -c ^processor /proc/cpuinfo)
gives me 35 signs/s and draws 4W more of power on AC-side

show temperature every second:

Code: Select all

watch -n1 cat /sys/class/thermal/thermal_zone0/temp
Last edited by Flagbit on Fri Mar 25, 2016 3:38 pm, edited 15 times in total.
-- My 2 Cents, Coin Heatsink: https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=141441
-- Snappy Pi 3: Coin Heatsink, 1300Mhz Overclocked stable (could void warranty), Ubuntu-Mate on USB-stick

pxgator
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Re: My 2 Cents: Coin Heatsink :)

Wed Mar 23, 2016 5:21 pm

Clever idea......thanks for sharing. Here is a link to some glue
that works very well for gluing on heatsinks.

http://www.ebay.com/itm/Large-9g-Therma ... 0872305451

Cheers
So what's all this RPi stuff anyhow? Well folks, it's a feat of engineering from
the UK almost as remarkable as the De Havilland Mosquito and the Colossus.

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allfox
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Re: My 2 Cents: Coin Heatsink :)

Wed Mar 23, 2016 5:25 pm

Wow, clever~

CNY is some kind of white metal coin, I'm not sure its capability of transporting heat.

Anyway, it looks cool~

stderr
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Re: My 2 Cents: Coin Heatsink :)

Wed Mar 23, 2016 5:39 pm

allfox wrote:CNY is some kind of white metal coin, I'm not sure its capability of transporting heat.
Obviously if you are using American pennies, you'd want to find one that is old enough to be built from actual copper and not zinc.

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Flagbit
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Re: My 2 Cents: Coin Heatsink :)

Wed Mar 23, 2016 6:16 pm

The best materials for heat conduction are (first is best):
silver
copper
gold
aluminium
...


Most heatsinks are made of aluminium because its cheaper, some of copper or with a copper core for better heat transfer.

edited.:
Afaik they can dissipate the heat through:
- radiation (as sitting next to a radiator)
- natural and forced air convection (like hot air going up because being lighter then cold air or using a fan)
- liquid in a closed circuit or a electrical nonconducting liquid
- heatpipes (as using a liquid gas to let it get vaporated at working temperature and let it flow by convection to a colder place and get liquid again)

A five cent coin would have a bigger surface exponated to the air.
A plane surface on the bottom would also improve heat conduction a lot.
-- My 2 Cents, Coin Heatsink: https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=141441
-- Snappy Pi 3: Coin Heatsink, 1300Mhz Overclocked stable (could void warranty), Ubuntu-Mate on USB-stick

dom
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Re: My 2 Cents: Coin Heatsink for Overclocking :)

Wed Mar 23, 2016 9:36 pm

Amusing. I've tried this with a pound coin, just placed on chip (no glue) and it does lower the cpu temperature by about 5 degrees.
I imagine some sort of thermal compound would help more.

stderr
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Re: My 2 Cents: Coin Heatsink :)

Wed Mar 23, 2016 9:48 pm

Flagbit wrote:The best materials for heat conduction are (first is best):
silver
copper
gold
aluminium
I think you left out diamond which is better than silver. The wife or girlfriend may frown upon raiding the jewellery case for heat sink supplies, however.

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Flagbit
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Re: My 2 Cents: Coin Heatsink for Overclocking :)

Wed Mar 23, 2016 9:54 pm

@dom
Only placing the 2 Cents on the chip without glueing, it lowered peak temperature from 75°C to 70°C.
So also 5°C..

Wikipedia says:
One pound United Kingdom
Value 1 pound sterling
Mass 9.5 g
Diameter 22.5 mm
Thickness 3.15 mm
Edge Milled, with incuse lettering
Composition Nickel-brass
(70% Cu, 24.5% Zn, and 5.5% Ni)


against
2 cents European Union
Value 0.02 euro
Mass 3.06 g
Diameter 18.75 mm
Thickness 1.67 mm
Edge Smooth with continuous groove
Composition Copper-plated steel

So yours should work much much better with a thermal compound in theory as also a euro coin should do

1 euro European Union
Value 1 euro
Mass 7.5 g
Diameter 23.25 mm
Thickness 2.33 mm
Edge Alternating segments, three smooth, three finely ribbed
Composition Outer segment: nickel brass.
Inner segment: three layers: copper-nickel, nickel and copper-nickel.
-- My 2 Cents, Coin Heatsink: https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=141441
-- Snappy Pi 3: Coin Heatsink, 1300Mhz Overclocked stable (could void warranty), Ubuntu-Mate on USB-stick

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Re: My 2 Cents: Coin Heatsink :)_

Thu Mar 24, 2016 9:26 am

I tried it with my Visa card. Didn't work.
American Express was slightly better.

Same with a five pound note. Would dollars be better?

Heater
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Re: My 2 Cents: Coin Heatsink :)_

Thu Mar 24, 2016 9:32 am

My bitcoins did not help either :)

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Flagbit
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Re: My 2 Cents: Coin Heatsink :)_

Thu Mar 24, 2016 5:02 pm

Coincidence ?
Would one of the small candles in a aluminium cup work good, because of the melting point of wax being around 46-68°C?
-- My 2 Cents, Coin Heatsink: https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=141441
-- Snappy Pi 3: Coin Heatsink, 1300Mhz Overclocked stable (could void warranty), Ubuntu-Mate on USB-stick

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solar3000
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Re: My 2 Cents: Coin Heatsink :)

Thu Mar 24, 2016 6:48 pm

stderr wrote:
Flagbit wrote:The best materials for heat conduction are (first is best):
silver
copper
gold
aluminium
I think you left out diamond which is better than silver. The wife or girlfriend may frown upon raiding the jewellery case for heat sink supplies, however.

I use diamond heat sinks all the time.
Antikythera

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Re: My 2 Cents: Coin Heatsink :)_

Thu Mar 24, 2016 9:19 pm

Sanding of filing the side that touches the CPU flat will improve heat transfer. The more ridges on the open air side the better though. More suface area means more heat transfer to the air. You can get the heat sink double sided thermal pads here, https://www.adafruit.com/products/1467 and other places. The thermal tape isn't as permanent as the glue and easily removable if you change your mind. Or want to try different objects as heat sinks. If you have an old dad motherboard kicking around, pull the chip-set heat sink off and use it. Trim it smaller with a dremel or hack saw if you like.

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solar3000
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Re: My 2 Cents: Coin Heatsink :)_

Fri Mar 25, 2016 12:11 am

The problem with that 'heat sink' is that it has just one surface. Not much to dissipate heat.
That and the fact that its not copper - just plated like others pointed out.
Antikythera

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Flagbit
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Re: My 2 Cents: Coin Heatsink :)_

Fri Mar 25, 2016 1:12 am

Hi,

yes, it lowers only temperature peaks e.g. at a overclocked SOC.

For daily use as a snappy office computer, it should be enough (as far as I tested until now).

Other bigger coins made of copper or aluminium should be much better.
Also it should improve most when used with a proper thermal glue/tape
eliminiating the air gaps beetwen the surfaces of the SOC and the heatsink.

A plain, bigger copper coin would already be as good as an small aluminium heatsink, I bet.
The difference between winged and plain is not that big when only used with natural air convection and not with a fan, afaik.

Kind Regards
Flagbit
-- My 2 Cents, Coin Heatsink: https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=141441
-- Snappy Pi 3: Coin Heatsink, 1300Mhz Overclocked stable (could void warranty), Ubuntu-Mate on USB-stick

zealousd
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Re: My 2 Cents: Coin Heatsink :)_

Fri Mar 25, 2016 4:49 am

If only there was room for a CPU cooling block and fan, my after market one is bigger then the board.

but interesting idea
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Flagbit
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Re: My 2 Cents: Coin Heatsink :)_

Fri Mar 25, 2016 9:38 am

The 10, 20 and 50 euro cents seem to be very good in heat conduction.
I will give one a try.
Its composition is 89% copper, 5% aluminium, 5% zinc, and 1% tin.[3]
https://en.wikipedia.org/wiki/Nordic_gold

ed.:
Maybe someone else will do, the loctite is tighter then I thought :)
I will stick to my 2 cents and maybe apply a magnet to its steel ;)
-- My 2 Cents, Coin Heatsink: https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=141441
-- Snappy Pi 3: Coin Heatsink, 1300Mhz Overclocked stable (could void warranty), Ubuntu-Mate on USB-stick

xeph20
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Re: My 2 Cents: Coin Heatsink :)_

Mon Jan 30, 2017 11:47 pm

Hello,

i'm very interested in this.
i live in the EU so i can use any euro coin
i have a pi zero
i also have thermal pads and thermal paste

What would work best ?
i also have a plastig case which should hold a pad or pad/coin combination well in place

or will the coin burn a hole in the plastic?


Thank you very much

ktb
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Re: My 2 Cents: Coin Heatsink :)_

Tue Jan 31, 2017 7:12 am

Even with the thermal tape, be careful if you ever try to remove it.

My B+:
Image

I can't say whether or not it got cracked from overclocking (Although possible, I never overclocked it to extreme levels and it always had a heatsink with fan -- after all, it was just a B+) or always had a little hairline fracture in it. From my perspective, the little piece on top of the chip snapped off while I was carefully pealing off a heatsink applied with 3M thermal tape (it had been on there a couple years). Anything is possible. I don't know if it's dangerous to keep using it. It happened recently and I haven't even tried booting it since that happened.

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Re: My 2 Cents: Coin Heatsink :)_

Tue Jan 31, 2017 7:51 am

xeph20 wrote:Hello,

i'm very interested in this.
i live in the EU so i can use any euro coin
i have a pi zero
i also have thermal pads and thermal paste

What would work best ?
i also have a plastig case which should hold a pad or pad/coin combination well in place

or will the coin burn a hole in the plastic?


Thank you very much
you really need cooling on a RPi-3 a RPi-0 will not need it
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alexeames
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Re: My 2 Cents: Coin Heatsink :)_

Tue Jan 31, 2017 7:54 am

To do a proper job of it, the processor needs to be screwed down tight :lol:

Image
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Re: My 2 Cents: Coin Heatsink :)_

Tue Jan 31, 2017 8:07 am

Makes it a bit difficult to move the Pi unless you use a short enough screw though Alex :roll: :D


Gordon

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Re: My 2 Cents: Coin Heatsink :)_

Tue Jan 31, 2017 12:03 pm

It's more complicated than this material is better than that.

For example, while copper is a better thermal conductor, aluminum radiates heat better. So in a passive cooling system an aluminum heatsink might work better than copper, but with a fan copper will usually be superior. And then there are the porous-ceramic heatsinks which have a lot more surface area than a comparably sized metal heatsink.

Diamond, however, will always work better, because when your wife finds out you popped the stone out of her engagement ring and glued it to your Raspberry Pi you will be out in the cold.
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TheWaterbug
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Re: My 2 Cents: Coin Heatsink :)

Tue Jan 31, 2017 3:53 pm

Flagbit wrote:The best materials for heat conduction are (first is best):
silver
copper
gold
aluminium
I thought gold was best. No?

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Re: My 2 Cents: Coin Heatsink :)_

Tue Jan 31, 2017 4:09 pm

Flagbit wrote:Maybe someone else will do, the loctite is tighter then I thought :)
When I was a young engineer there was me and my boss in one office. We had rotary phones and they slid around when you tried to dial, so I Blu-Tak'd mine down. My boss used my phone once and realised it didn't move, saw the bottle of Loctite sitting next to it and jumped to the wrong conclusion. I watched him in bemusement as he glued his phone down. When we moved offices, his phone went with a bit of desk still attached to it. Mine didn't.

Blu-Tak is, however, a poor thermal conductor.

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