Control output power based on input temps?

I'm looking to use an Arduino board to control power output based on ambient temps inside a case.

The fan (one or two) are 0.18A 12V.
I have the following Arduino boards:
Mega R3
Uno R3

I have a Power Supply for the Fans and Arduino will be this 24V unit.

I have these temp/humidity sensors.

I have 5V DC relays to 125v 5A and 10A.

I think I'm going to need something to convert the 24V DC output to the input current for one of the Arduino's above ... suggestions? The Uno operates on 7V to 12V DC 1-2A I think?

I'm not sure what Arduino board to use from the list above (guessing Uno), suggestions?

The basic purpose of the circuit is to increase output to the fans as the temps increase. Now I realize there are probably fan controllers that might be able to do this for me, but I want to have my own circuit (that I may update later to include temps display and power curve adjustments and humidity adjustments).

Cheers, Rob.

Wrong. You need converters, likely buck, converters delivering 12 volt to the fans and the corresponding 5 volt to the controller, UNO or mega. Micro and Leonardo I don't have in the memory. Watch out if they need 3.3 volt Vcc.

This is a suitable project instead of buying expensive ready made controllers.

Computer fans these fans accept Arduino output to control speed

Because You will run two relay modules and the sensors I recommend a 24 to 5 volt buck converter delivering 5 volt.
The internal 5 volt converter on an UNO, a mega, will be at the edge to overheat if 12 volt Vin is used.

Forget 24 draw low power at 12 volt.

Before you spend any more time, make a simple sketch wiring diagram.

Many things will clear themselves up.
Are the fans 3 or 4 wire? Post a photo maybe

As a note relays may be overkill for this project.

Great responses ... but you'll need to enlighten me on:

  1. Whats "buck converters"? Source?

The 24V DC is all that's available as a power source so I'll need to work with that from that PSU.

Yes the fans are 120mm computer fans (0.18A 12V 2350 rpm PWM (4 wire) Corsair.

Cheers, Rob.

the 4 wire connection and sample sketch.

a buck converter is a 24VDC to 12VDC device
or pretty much any higher DC voltage to a lower DC voltage.

a boost would be a higher voltage output.

1 Like

Awesome, thank you!

Does anyone know if there are Arduino component libraries for Autodesk Fusion 360? When I try to add Arduino parts I get nothing in the search in Fusion 360.

Cheers, Rob.

Hello and good morning
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