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Re: ZX81 cooling fan

Posted: Mon Nov 13, 2017 7:34 pm
by Moggy
A couple of pics of 12v fan in case which is now connected to 5v and both cases temporarily put back together.

The zeddy I'm using is an H4th one with switching regulator connected to an issue one ZXpand and since 7PM has been running through an DO LOOP just over a billion iterations long and so far so good, the fan is near silent.

Will let this stew for 2-3 hours and check if the case hot spot above the ULA appears.

Re: ZX81 cooling fan

Posted: Mon Nov 13, 2017 9:54 pm
by Moggy
The zeddy has now been running like a dream for the last 21/2 hours and I'm pleased to say I can't detect any discernable heat spots on the upper case by touch which I certainly can without fan cooling,not very scientific I know but proof I think that some cooling of the ULA is taking place and that there is definite air movement through the case and that Lardos' proposition has much merit so much so that if I can find a more tidy method of modding the lower cases on my two standard 81s' so that the fan aperture looks more professional then mod them I will.

I may even go as far as making a small opening on the back of the zeddy so the incoming air goes straight over the ULA,we shall see.

Thanks for the inspiration Lardo I have really enjoyed this little experiment. :D

Re: ZX81 cooling fan

Posted: Mon Nov 13, 2017 10:25 pm
by Lardo Boffin
You are more than welcome Moggy.

And if you happen to know the name of a good quality fan that I can buy somewhere then all the better! ;)

Re: ZX81 cooling fan

Posted: Tue Nov 14, 2017 7:57 am
by siggi
Hi Moggy and others
what do you think about that type of fan?

https://www.ebay.de/itm/Notebook-Radial ... SwZB9aAdCj

So it would be possible to blow out the warm air through a slot at the left or right side of the Zeddy case (below the keyboard ). Thus the Zeddy does not need long "feet" to let the air flow beneath its bottom.

The other advantage would be: if you put your tea or coffe pot beside the Zeddy (into thee blown out warm air stream), the ULA could also be used to warm up your drink ;-)

Siggi

Re: ZX81 cooling fan

Posted: Tue Nov 14, 2017 9:44 am
by mrtinb
Moggy wrote:
Mon Nov 13, 2017 7:34 pm
A couple of pics of 12v fan in case which is now connected to 5v and both cases temporarily put back together.
On the second picture you need to put the rubberfeet back on. Otherwise the fan is useless. :)

Re: ZX81 cooling fan

Posted: Tue Nov 14, 2017 10:18 am
by Lardo Boffin
siggi wrote:
Tue Nov 14, 2017 7:57 am
Hi Moggy and others
what do you think about that type of fan?

https://www.ebay.de/itm/Notebook-Radial ... SwZB9aAdCj

So it would be possible to blow out the warm air through a slot at the left or right side of the Zeddy case (below the keyboard ). Thus the Zeddy does not need long "feet" to let the air flow beneath its bottom.

The other advantage would be: if you put your tea or coffe pot beside the Zeddy (into thee blown out warm air stream), the ULA could also be used to warm up your drink ;-)

Siggi
I like that idea! If we put it to blow out on the left I could have:-
Spectrum 128k toastrack - coffee - ZX81 with radial fan

Lovely warm coffee all day long! :D

Re: ZX81 cooling fan

Posted: Tue Nov 14, 2017 1:45 pm
by Moggy
siggi wrote:
Tue Nov 14, 2017 7:57 am
Hi Moggy and others
what do you think about that type of fan?

https://www.ebay.de/itm/Notebook-Radial ... SwZB9aAdCj

So it would be possible to blow out the warm air through a slot at the left or right side of the Zeddy case (below the keyboard ). Thus the Zeddy does not need long "feet" to let the air flow beneath its bottom.

The other advantage would be: if you put your tea or coffe pot beside the Zeddy (into thee blown out warm air stream), the ULA could also be used to warm up your drink ;-)

Siggi
That does look like a rather good solution as I'm sure the dimensions are ok, but the only down sides I can think of are that a 5v fan running off a 5v supply means it will be running at full speed so may be quite noisy whereas a higher voltage fan running from a lower voltage is indeed much quieter plus this fan may run into the problem I had when the case was put back together causing insufficient headroom above the fan leading to a lack of airflow. It wasn't until I put the fan through the case that sufficient airflow became apparant.

@Lardo.

I will continue search for a good standard ball bearing fan in the meantime.

@Martin.

I did replace the feet for the test.

Re: ZX81 cooling fan

Posted: Tue Nov 14, 2017 2:50 pm
by Paul
Actually the third pin should be used to control the speed of it.
But I have no idea how...
Maybe use a pic or arduino to set the speed, in relation to the internal heat. I leave it up to you which point you will measure.

The downside of this again is that the pic has more processing power than the zeddy :twisted:

Re: ZX81 cooling fan

Posted: Tue Nov 14, 2017 3:42 pm
by siggi
Paul wrote:
Tue Nov 14, 2017 2:50 pm
Actually the third pin should be used to control the speed of it.
But I have no idea how...
Maybe use a pic or arduino to set the speed, in relation to the internal heat. I leave it up to you which point you will measure.

The downside of this again is that the pic has more processing power than the zeddy :twisted:
I think, that the Z80 itself would be able to do that: it has a /RFSH ouput to indicate, that it needs to be refreshed, when it gets too warm inside the Zeddy :mrgreen:

Re: ZX81 cooling fan

Posted: Tue Nov 14, 2017 9:34 pm
by Moggy
Just a quick addition to previous posts.

Tonight I ran the zeddy under the same conditions but minus fan and after the same elapsed time period there is a definite hot spot on the top case above the ULA position so I can only conclude that fan cooling with a low speed fan is indeed viable and once I can find a "proper" method to case cut-fan-fit and cut suitable air inlets on the case front etc I may delve into this a bit more.