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Temperature sensing fan control for an enclosed media cabinet


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#1 unt1tled

unt1tled

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Posted 10 July 2011 - 05:27 PM

Excited newb here. I'm working on ventilating my media cabinet with some netduino magic and a couple of laptop coolers.

I have two Rosewill Notebook Coolers that I'll be building into the base of the cabinet. They're each rated 5V, 0.25A.

Now I did manage to get the temperature sensor wired and working (awesome!), but I'm not quite sure where to begin with wiring up the fans.

  • I'm guessing it's not a good idea to connect them both to the netduino's 5v pins because it's above the its current threshold?
  • If so, do I rather need to wire them up to a relay somehow? (Will this one do?)
  • If I use the relay, is a separate power source necessary, or can it share with the netduino? I was planning on using a FlipIT as a 5v power source.
  • Is there anything guide or anything else I need? I've read a guide on relays, but wasn't sure if that was superfluous to what I'm doing.
Any help will be appreciated!

Cheers

#2 Nevyn

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Posted 10 July 2011 - 06:22 PM

  • I'm guessing it's not a good idea to connect them both to the netduino's 5v pins because it's above the its current threshold?<li>Is there anything guide or anything else I need? I've read a guide on relays, but wasn't sure if that was superfluous to what I'm doing

It is not a good idea to do this for more than the reason you specifed. When a motor stops it can generate a back EMF. This can put a large pulse of current back into the Netduino. In fact then using a transistor as a switch it is advised that a diode is put into the circuit to offer just this kind of protection.

There are specialist circuits for controlling motors - have a look for H-Bridges - they aren't that expensive. I can't comment on thier use as I have not needed to use one but that is where I'd start if I was working with motors.

And welcome to the community.

Hope this helps,
Mark

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