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What resistor is needed to protect a fan in parallel with a peltier?

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orion456

Member
Joined
May 31, 2004
I have a 12v 10A power supply which will power a 60 watt peltier.

I want to tap that 12v to run a .24A fan to help cool the peltier. Do I need a resistor to protect the fan or is that unnecessary?
 
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Ben333

Folding for Team 32!
Joined
Feb 18, 2007
I've never heard of that...? I've ran peltiers off PC power supplies. And the PC supplies had other things hooked up to them along with the pelts... :shrug:

What would the resistor do? Slow the fan down... and offer some current limiting.
 

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
Unless its a fan you're really worried about protecting I'd just "run it". I've had PC fans on some dirty power before. Cheao-o "wall warts", over-volted sometimes by double their rated voltage. Car batteries, you name it. It's really just a brushless motor. Not gonna kill it unless you really over volt the thing.
 
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orion456

orion456

Member
Joined
May 31, 2004
I've never heard of that...? I've ran peltiers off PC power supplies. And the PC supplies had other things hooked up to them along with the pelts... :shrug:

What would the resistor do? Slow the fan down... and offer some current limiting.

I thought if the peltier failed then more current would go thru the 12v fan. But I guess the fan will limit the current on its own?
 

Lochekey

Senior Pink Member
Joined
Sep 13, 2015
The fan will only pull the current it needs, the power supply will not push excess current into the fan. The power supply will only supply the amperage that connected components are pulling.
 
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orion456

orion456

Member
Joined
May 31, 2004
The fan will only pull the current it needs, the power supply will not push excess current into the fan. The power supply will only supply the amperage that connected components are pulling.

Is it possible for the fan to become a short circuit? In which case a small resistor in series with the fan will prevent the current from going damaging the power supply?
 

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
Bingo. But technically, the power supply would push the fan whatever it would take. So if the fan some how could take more current, the power supply would supply it till the wires melted or a solder joint broke.

But this scenario is inside EVERY computer of every member on this forum. And nobody has extra protection for their fans :) You're fine, you don't need any extra protection. Everybody has .25A 12V fans with 20 - 30 amps of 12V power just waiting to fry them, it just isn't likely.

You say the supply is 10 amps though, how many watts is the peltier? And what voltage range is it designed for?
 

JrClocker

AKA: JrMiyagi
Joined
Sep 25, 2015
Is it possible for the fan to become a short circuit? In which case a small resistor in series with the fan will prevent the current from going damaging the power supply?

You have a 12V @ 10A = 120 W power supply.

If the fan becomes a short circuit, it will pull all 10 A. In this case, you would need a 120 W resistor to "protect" the fan. A 120 W resistor is VERY LARGE.

If the fan becomes a short circuit, the wiring inside the fan will melt, and it will stop being a short circuit!

If you want to do anything for the fan, you should stick a fuse inline with the fan. For a 0.24 A fan, I would recommend a 1 A fuse. This is the proper way to "protect" the fan.

My advice...don't worry about it!
 
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orion456

orion456

Member
Joined
May 31, 2004
I'm curious, what are you planning on cooling with a 60w TEC?

A ccd camera for some long exposures. The ccd doesn't need much cooling but its attached to a piece of metal that does need a lot of cooling.
 

Alaric

New Member
Joined
Dec 4, 2011
Location
Satan's Colon, US
If the fan becomes a short circuit, it will pull all 10 A. In this case, you would need a 120 W resistor to "protect" the fan. A 120 W resistor is VERY LARGE.

It will look like a glass tube with a soft metal strip inside. Usually called a "fuse".