In message , rick
writes
Have knocked up a fan speed controller ... where temp control speed ...
and hence cooling.

The temp sensor is a Thermistor - the cct board is inside a metal case,
I'm thinking that it might not be responsive enough if the thermistor
is inside the case.........

I could arrange to glue it to inside of case lid, or even onto outside
of case lid ........ anybody done any thermistor based projects ...
just wondered what is normal.

45 years ago:-(

We were not attempting close temperature control. The thermistor was
potted inside a short length of metal tube and then clamped to the fins
of refrigeration plant.

--
Tim Lamb