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DC Brushless Fan Current

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ChinaVoodoo

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When I've picked up an old computer fan and looked for a power source for it, I've gone to the thrift store and picked out old transformers from phones, answering machines, etc. and chosen them based on total watts, ie. amps x volts, according to the watts on the fan. However it occurred to me that the DC fans in my darkroom on my work truck are 12V, 0.8A, and are wired indirectly to the truck battery which obviously puts out way more current than 0.8A.

So really, so long as current is sufficient, voltage is all that matters when pairing a DC fan with a transformer, correct?
 

Matty

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As far as I've ever seen. I used to work as a computer hardware technician, fans were one of the things I dealt with. The volts are the most important so that the fan turns the right speed. 2nd point is if the power source puts out less amps the power source could/will overheat. I've never had a fan overheat from too many amps but the rest of a computer doesn't like it very much.
 

Jack in NB

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The computer fans (removed from the power supplies) I had in my former kiln were all 12 v and 0.18 - 0.2 a current draw.

I used 12 v plug-in power transformers rated 12 v DC 200 ma or 300 ma current ratings. The only minor caution was rewiring to get the correct polarity.

So you're correct - sufficient current, correct voltage - and polarity.

Jack
 

Matty

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They don't need much to run, I used to go through boxes of salvaged fans and try them all with a 9v battery just to see if they turned well.
 

ChinaVoodoo

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They don't need much to run, I used to go through boxes of salvaged fans and try them all with a 9v battery just to see if they turned well.

Often princess auto will have piles of identical fans. I was thinking a guy could use a single power supply to run a large number of fans. I have a couple tiny 12v snail fans that work really well. Ten of them in my curing shed would have the air flowing pretty evenly throughout.
 

ChinaVoodoo

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If you have electricity to your curing shed, then a single, cheap box fan will get the job done.

Bob

Two fans wasn't enough last year. Even though it was well insulated, heat and moisture were not necessarily evenly distributed. Ten small fans are excessive, but I do need to improve the system. The new shed I'm building will alternate between flue curing and air curing. Heating needs to be even. I also want to use it as a massive kiln over the winter. Outside the shed will be well below zero, even during the curing phase. Given that I'm not a master builder, and the massive temperature gradients involved between inside and outside, I want to err on the side of extra circulation.

More importantly, I don't want to take up space with large fans. Small fans can be implemented without taking up room.
 

DGBAMA

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Amperage of the power supply doesn't matter, as long as it is more than the fan rating. 12v is 12v. The Ah or MAh rating of the motor is what it consumes.

1A (amp) = 1000Ma (milliamps).

So, a 12v transformer with a 2A output can run 4 12v fans rated at 12v 500Ma.

Most DC motors will take a 20% overrun voltage without a problem, so a 14v transformer is fine too.

A transformer that has less amperage output than the draw of the motor it is powering is where you end up with burned up motors or transformers.
 

DGBAMA

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I have 2 computer fans in my curing chamber, one is 750ma the other 500ma, both 12v. This is 1250ma consumption. For three seasons they have ran on a 14v 2a (2000ma) recycled power supply.
 
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