On 2019-01-12, Bernd  wrote:
> Am 11.01.19 um 10:36 schrieb Bernd:
>> Hi,
>>
>> if I search for cases for my RasPi 3 B+, I found the most cases has
>> additional heat spreader and fan. It is fact that a RasPi 3 B+ needs
>> additional cooling? (Fans are noisy ...)
>
> Thx, for your comments. Meanwhile I have found how to measure the temp
> from the RasPi. This and the tip to use a 5V fan but connect to 3.3V
> does the trick.
>
> Thx for the ideas!
>
> Bernd

There is another way to slow down and thus reduce the sound level
from a fan (or blower).  Connect a resistor and electrolytic
capacitor in parallel, then connect that combination in series
with the fan.  When power is first turned on, the fan sees full
voltage to get it started.  Then, the fan voltage is gradually
reduced to a lower level to keep it running more quietly.  The
value of the resistor controls the long-term fan voltage and thus
the noise level.  The value of the capacitor controls how long
the fan receives higher starting voltage.  Make sure the
resistor's power rating is sufficient for the long-term run
current.

Turning power off and on too quickly can outsmart that simple
circuit.  A more complex circuit could avoid that shortcoming if
needed.  The simple circuit has worked well enough in an A/V
switcher I designed and built a couple of decades ago.

HTH

--
Robert Riches
spamtrap42@jacob21819.net
(Yes, that is one of my email addresses.)

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