Temperature controlled fan project for beginners

[queennikki1972]

I just wanted to say that this is a good project for beginners. I really enjoyed it. I am more curious about the specs of the NTC 472 (4.7K) Thermistor.. surface heat tolerance. And if other types of thermistors could be used in the same circuit, such as mounting on a large heat sink with shrink tubing and a screw.

Here is a link to the thermistor used.
https://www.ebay.com/itm/20-Pcs-NTC-Thermistor-Resistor-NTC-MF52AT-4-7K-OHM-5-B-3950K-1/392365363405?hash=item5b5acc50cd:g:WWcAAOSwTm1dQ5w5:sc:USPSFirstClass!76116!US!-1

[soldar]

As you say, an easy project for a beginner. The comparator turns the fan on/off.

I would prefer a proportional control where the speed of the fan is proportional to the temperature deviation. This allows the fan to run continuously and more slowly and quieter rather than stop and then blast. 

[Zero999]

I would prefer a proportional control where the speed of the fan is proportional to the temperature deviation. This allows the fan to run continuously and more slowly and quieter rather than stop and then blast.

Yes, that's a good idea, but it will no longer be a beginner project. Proportional control of fans will save power, but for something small, it might not be worth the extra complexity.

[Kleinstein]

Proportional control is a little more complicated, as it needs a suitable gain factor.  As this is only 1 value to get right one could still go for try and error.

Even the simple on/off control may want some hysteresis to avoid to frequent on/off. So even this solution may need 1 parameter to adjust.

[soldar]

I would prefer a proportional control where the speed of the fan is proportional to the temperature deviation. This allows the fan to run continuously and more slowly and quieter rather than stop and then blast.

Yes, that's a good idea, but it will no longer be a beginner project. Proportional control of fans will save power, but for something small, it might not be worth the extra complexity.

My concern is noise, not power consumption.

Copying a proven design should not be complicated at all.

Even a simple design should not be complicated.

Really simple is to have two or three steps. Take a 12 V fan and run it at 0 V, 6V, 12 V depending on temperature.

But with an Op amp it should be very easy to design a true proportional control.