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On Friday, 22 May 2015 16:37:01 UTC+1, Andrew Mawson wrote:
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On Friday, 22 May 2015 14:17:19 UTC+1, rick wrote:
On 21/05/2015 20:43, nt wrote:

I take it this is a classified project,

Not sure why you think that .... this is a home build project to
control

well, you avoided giving us the relvant info, until now

the speed of a computer fan ... thus allow cooling of a comms cupboard
that gets too hot in summer.

The circuit is based on the cct he
https://www.dropbox.com/s/rewcotpvkd...rcuit.jpg?dl=0

They use a bare board ... for safety & longevity building this into al
aluminium case. That is why question of where to mount thermistor
comes
from.

It would work gluing it to the case, but woudl give a time lag in
operation, resulting in poor temp control and wasted energy. I'd put it
near top of cabinet in the airstream.

Some good old classic components in that circuit

I can't see anything on that page


NT

Basically a 741 op amp comparing a fixed divide chain to one with a
thermistor in it - 'supose it could have been even more classic and used a
709

Andrew