ZX81 cooling fan

Discussions about Sinclair ZX80 and ZX81 Hardware
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1024MAK
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Location: Looking forward to summer in Somerset, UK...

Re: ZX81 cooling fan

Post by 1024MAK » Mon Nov 13, 2017 12:58 pm

1024MAK wrote:
Mon Nov 13, 2017 12:30 pm
As for your existing fan, if you have some rubber O rings of a suitable size, you could use these. That is what is used on some computer fan mounting kits.
But note that O rings are normally used between the fan and the bolts/screws that are used to fit the fan to the enclosure/case or heatsink...

Mark

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1024MAK
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Location: Looking forward to summer in Somerset, UK...

Re: ZX81 cooling fan

Post by 1024MAK » Mon Nov 13, 2017 1:08 pm

Lardo Boffin wrote:
Mon Nov 13, 2017 12:24 pm
For the electronically minded - if we reduce the voltage to the fan will it just reduce the speed a little?
I am wondering whether there will be a good tradeoff between speed (and noise) and cooling ability?
Short answer, normally yes. Either use a suitable resistor or use a lower supply voltage.
Long answer, not always, due to the "motor" being a brushless type. Inside, there is an electronic circuit, which switches each coil on and off in a sequence, this causes a permanent magnet to try to follow the magnetic field generated by each coil. So the resistor cannot be too high a value/the supply voltage cannot be too low, otherwise the magnetic field strength from the coils will be too low to attract the permanent magnet...

Mark

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Paul
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Location: Germanys west end

Re: ZX81 cooling fan

Post by Paul » Mon Nov 13, 2017 1:23 pm

I think about something like this :

https://www.reichelt.de/Luefterzubehoer ... ARCH=%252A
In theory, there is no difference between theory and practice. But, in practice, there is.

Lardo Boffin
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Re: ZX81 cooling fan

Post by Lardo Boffin » Mon Nov 13, 2017 1:45 pm

I have some silicone washers which are the right size just no bolts narrow enough. :evil: The smallest I have is m3.5 but I need m3.
A gasket type approach would be good but I can’t find any that are anywhere near small enough.
Does anyone know of any good brand of cooling fans? That are this small.. The one I have is 25 by 25 by 10mm. I think 7.5mm would be better given the clearance and additional height taken up by the vibration damping.
ZX81 iss 1 (bugged ROM, kludge fix, normal, kit)
Iss 3 with ZXVid, another in nearly perfect box
TS 1000 iss 3, ZXPand AY, ZX8-CCB & ZX-KDLX
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Spectrum 48k
Toastrack + DIVMMC future

Moggy
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Re: ZX81 cooling fan

Post by Moggy » Mon Nov 13, 2017 1:58 pm

Rather than faff around with resistors or making the job more complicated than it needs to be just use a 12v fan tapped off 9v.

I have done this on a Fuller cased zeddy result adequate air movement and near silent running, the fan doesn't need to running at 10,000 rpm to shift enough air.

Cheap/small fans by nature are badly balanced and this is exaggerated when run at full speed as I've said before a gentle throughput is all that's required not a hurricane.

Lardo Boffin
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Re: ZX81 cooling fan

Post by Lardo Boffin » Mon Nov 13, 2017 2:21 pm

Moggy wrote:
Mon Nov 13, 2017 1:58 pm
Rather than faff around with resistors or making the job more complicated than it needs to be just use a 12v fan tapped off 9v.

I have done this on a Fuller cased zeddy result adequate air movement and near silent running, the fan doesn't need to running at 10,000 rpm to shift enough air.

Cheap/small fans by nature are badly balanced and this is exaggerated when run at full speed as I've said before a gentle throughput is all that's required not a hurricane.
Thanks. Do you know any good quality 12v fans that are ideally 25 by 25 by 7.5 or failing that 25 by 25 by 10? I guess we could go to 40 by 40 by 10 with a little surgery...
ZX81 iss 1 (bugged ROM, kludge fix, normal, kit)
Iss 3 with ZXVid, another in nearly perfect box
TS 1000 iss 3, ZXPand AY, ZX8-CCB & ZX-KDLX
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Spectrum 48k
Toastrack + DIVMMC future

Moggy
Posts: 1514
Joined: Wed Jun 18, 2008 1:00 pm

Re: ZX81 cooling fan

Post by Moggy » Mon Nov 13, 2017 2:30 pm

Lardo Boffin wrote:
Mon Nov 13, 2017 2:21 pm
Moggy wrote:
Mon Nov 13, 2017 1:58 pm
Rather than faff around with resistors or making the job more complicated than it needs to be just use a 12v fan tapped off 9v.

I have done this on a Fuller cased zeddy result adequate air movement and near silent running, the fan doesn't need to running at 10,000 rpm to shift enough air.

Cheap/small fans by nature are badly balanced and this is exaggerated when run at full speed as I've said before a gentle throughput is all that's required not a hurricane.
Thanks. Do you know any good quality 12v fans that are ideally 25 by 25 by 7.5 or failing that 25 by 25 by 10? I guess we could go to 40 by 40 by 10 with a little surgery...
Just nipped into attic and removed a chipset fan of the same dimensions as yours,Lardo, and quickly wired it up to the 9v on my test 81 with xpand and zonx box connected and at 9v running I was surprised to find it still a tad noisy but at 5v really quiet and still a good airflow so will continue this evening to fit to a normal zeddy and post results.

As for suppliers I will continue searching this afternoon (forget Farnell silly money) then report back.

Lardo Boffin
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Joined: Sat Nov 26, 2016 1:42 am

Re: ZX81 cooling fan

Post by Lardo Boffin » Mon Nov 13, 2017 2:45 pm

Thanks Moggy. I’m on limited time to find these things at the mo!
ZX81 iss 1 (bugged ROM, kludge fix, normal, kit)
Iss 3 with ZXVid, another in nearly perfect box
TS 1000 iss 3, ZXPand AY, ZX8-CCB & ZX-KDLX
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Spectrum 48k
Toastrack + DIVMMC future

Lardo Boffin
Posts: 662
Joined: Sat Nov 26, 2016 1:42 am

Re: ZX81 cooling fan

Post by Lardo Boffin » Mon Nov 13, 2017 3:02 pm

I forgot to say earlier that after 3 hours of running The Gauntlet I opened up the case and quickly did the highly technical finger temperature test.
I believe that just too hot to touch is around 60 degrees C and it was only pleasantly warm to the touch so still nice and cool.
ZX81 iss 1 (bugged ROM, kludge fix, normal, kit)
Iss 3 with ZXVid, another in nearly perfect box
TS 1000 iss 3, ZXPand AY, ZX8-CCB & ZX-KDLX
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Spectrum 48k
Toastrack + DIVMMC future

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Andy Rea
Posts: 1268
Joined: Fri May 09, 2008 1:48 pm
Location: notts UK

Re: ZX81 cooling fan

Post by Andy Rea » Mon Nov 13, 2017 3:04 pm

No no no your all wrong... you gotta go big :D

https://youtu.be/EM2G5vLGcQQ

:mrgreen: :mrgreen:
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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