DIY Adjustable Fan Controller

[Indycars]

Automatic fan controller circuit


This circuit will turn on/off 12V DC fan or CPU fan when temperature above normal
temperature.You can set the turn on temperature by adjusting VR1. This circuit use
an NTC (Negative temperature coefficient)which is a thermistor is one in which the
zero-power resistance decreases with an increase in temperature. So If temperature
increases the voltage at pin 3 on LM311 will decrease .The resistance of NTC is about
10K at 25'c.

VR1 should be multi-turn potentiometer type such 10K/25 turn link

http://diagramdigital.blogspot.com/2014 ... rcuit.html


This controller would most likely not be able to control a radiator fan
directly, but it could control a relay that controlled a radiator fan.

 

[grumpyvette]

Admittedly this may be a dumb question ,while I LIKE THE ENGINEERING, I'm simply not seeing the NEED FOR THE application??!

but if I need a fan to cool a radiator, oil cooler or some component that requires a fan,I generally want as much air flow over its surface as I can get to maximize heat transfer rates, so why would I prefer it to run at a lower rpm and pull less airflow, while its in operation, vs have a thermal limit switch that is set too turn on at a set temp threshold limit of lets say 180F that turns it on, and a switch that's set to turn off at 170F? but operate at max capacity too remove and transfer heat while its intermittently on and operating?
THIS IS A GOOD VALUE

https://www.northerntool.com/shop/t...MIq4Gj3qeW2AIVVrXACh3l2QRxEAYYCCABEgK4afD_BwE
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[Indycars]

The above circuit does not control the fan speed, it only turns it on or off depending
on the temperature.

The Flexalite controller that I do have on my car does what you are talking about. It
comes on at 60%, then over the next 10°F it ramps up to 100% fan speed. It maybe
more marketing, but its less shock to the system when it does come on.

The bigger advantage would be a more constant temperature, since the fan only runs
fast enough to maintain temperature. Not a big deal, but some benefit is derived
from this type of controller.

 

[grumpyvette]

thanks! got it!