How to on computer fans?

[Anonymous]

Please Help. I am curious as to wiring the computer fans to my canopy I'm building for my MH's. I know there are some fans (2- 3" fans ac adapter and mounts) on Ebay already assembled for $38.50 shipping included. However I also know I can get a computer fan which looks Identical for around $3.00 a peice. Please help me figure out the path of least resistance. Thanks, Oh yeah and I don't want to have to worry about burning down my house.

 

[Anonymous]

Did you check the connection? Don't computer fans have that special plug that goes into the power supply in the case rather than terminating in a plug for an outlet?

 

[c0yote]

The computer fans also normally run at 12 volts.

 

[Anonymous]

Okay, ** STANDARD DISCAIMER I"M NOT AN ELECTRICIAN SO IT AIN'T MY FAULT! blah, blah blah."

okay, that being said,

Take your $3 computer fan. (I use enermax, they're really quiet.) Read the raiting. it will say 12vdc .XXXamps. (mine say .17a)
Convert that number to milliamps. (mine=170ma)
Round it up to the next hundred. Mine=200ma.

Go to radio shack, Tell them you want a 12vdc XXX milliamp adapter. Pay their absorbant $12 or so. (Or find one cheaper at a hardware store. I paid $3.) Don't care about what plug it has, you're going to cut it off anyhow.
Also, if you don't have soldering iron and solder, or 20guage butt splice connectors and a crimper get them too. (whichever is easiest for you.)

Take all your stuff home and cut the plug off the 12v adaper.
Find out which wire is positive, and which is negative.
Cut the plug off the fan. One wire will be positive, one negative. On mine, one wire AFTER the adapter is red, and one is black. Red is +, so I just matched up which wire from the fan plugs into the red wire.

Solder or butt-splice the two positive sides together, then electrical tape the connection. (or heat shrink), then repeat for the negative. (make sure it isn't plugged in btw.)

Whallah. working fan.

B

 

[Fl_Seagull]

Wire nut work wonders and with 12 volts you won't get electrocuted. Just look for the small ones made for 22-24 gage wires. The last ones I used where white but I think the standard color is gray. A little caulk to seal the wires will prevent corrosion.

 

[taikonaut]

Looks like you are all set there. I also recommand, FWIW, low voltage 12DC fans.

 

[Anonymous]

Thanks guys I'll let you know how it turns out. Cross your fingers

 

[PeeJ]

Of course, you could gut an old computer. I'm sure plenty of people have a power supply they could sacrifice.

 

[taikonaut]

That's the route I took. The case was used for housing my MH ballast, and the PS was used to power the fans.

 

[kronikwisdom]

Take all your stuff home and cut the plug off the 12v adaper.
Find out which wire is positive, and which is negative.
Cut the plug off the fan. One wire will be positive, one negative. On mine, one wire AFTER the adapter is red, and one is black. Red is +, so I just matched up which wire from the fan plugs into the red wire.

Umm... by my question you can tell i'm not electrician.. so.. How do i know which one is positive and which one is negative?!?

Can i use an old plug for something else and just cut the cord off?

I'm only looking to connect two computer fans together...
1)dc12v, .08a
2)dc12v, .10a


Can I use two different fans for this setup or should i just go buy a few new ones? Yes, I'm rambling on so someone please point me in the right direction.. THANKS.. .']

 

[Anonymous]

The color of the wire should tell you about the polarity, but for most powersupply, they are both black wires. :roll:

Anyway, if you are using a DC fan, you will know you got the two wires reversed: The fan is spinning the opposite direction!

 

[kronikwisdom]

If it possible to use an 12v adapter from an old router? Or is there a specific type of adapter that I need to use?!?

 

[Anonymous]

Yes, just make sure the voltage and amp is enough to power the fan. And if you have a DC fan, make sure the powersupply is also DC, etc.

 

[cindre2000]

I am actually installing a fan controller for the 120 I am building. The only problem is that the temperatures are have a preset range of about 65-75, 85-95, & 110-125 that determine the amount of power put into the fans. I just wish there is some way to reprogram the thing so I can put them at a better aquarium range rather than computer range [65-75, 75-85, & 85-95].

 

[Anonymous]

If you are handy, you maybe able to put a resistor in series with the thermosist to offset the temperature setting, but yeah, it is much easier if there is an easier way to customize the setting yourself.

 

[cindre2000]

I am wondering if I might be able to hack into the software and modify the chart.

 

[IslandCrow]

Take your $3 computer fan. (I use enermax, they're really quiet.) Read the raiting. it will say 12vdc .XXXamps. (mine say .17a)
Convert that number to milliamps. (mine=170ma)
Round it up to the next hundred. Mine=200ma.

Is the milliamp rating you get from the above formula just the minimum you need. For example, in the scenario above, if you got a 12V, .5 Amp adapter, could you use that? Also, what if you wanted to run two fans. Could you just get a 400ma converter and splice the wires from the two fans together to connect to it?

OK, one more question. If you had a converter that could increase or decrease the voltage, would that have a corresponding effect on the speed of the fan?

 

[felch]

I am wondering if I might be able to hack into the software and modify the chart.

Surely You can. What chip lies inside the controller? If it is a PIC, that's my favourite. Disassemble, if no code protection bits set, think a little bit and recompile. Unfortunately they usually set protection, then one should write own code. Not very complicated.

Btw, computer fans do not reverse rotation if powered wrong (+ goes to - ).
If you don't have a multimeter handy, buy some LED and a 1k resistor. Connect them in series. Connect this "tester" to your supply. If led does not light up, reverse polarity. Now, when led is light up, taller leg of LED shows positive output of supply.

 

[Sublime-1]

Island Crow and Others,


The 12vdc fans run off Milliamps. Meaning 500 milliamps, would be .5 amps.

So if the fan is rated at 100 milliamps, you need to run a bunch of them in series, in order not to over load and smoke them.

If you do however, run them "in series" you could get away with a bigger current Power Supply. Also, if you go to Frys, they have 120v AC fans for about $17 - $25 from 3" up to 12" (seriously.)

To run in series, rather than take +/- and run from +/-, take fan one red wire and connect to fan two black wire, then take fan one black wire and connect to (-) power supply line, and take fan 2 red and connect to (+) power wire.


This runs the fans "in series" meaning that the load is doubled, therby reducing the current exponentially to each fan.

This would enable you to get away with running them at the higher load.


BD

 

[felch]

So if the fan is rated at 100 milliamps, you need to run a bunch of them in series, in order not to over load and smoke them.

???? Since what time? If you connect any loads in series overall resistance is ths sum of all loads (fans in our case) resistances which is naturally bigger number than the one in case of one load. So overall current consumed by this circuit is reduced. No fear of overloading anything at all!
Another thing is that now every fan gets a lot smaller voltage (if you should have 2 fans, they'd both get about 6 V if powered from 12V. This could be too low for normal start-up. If you have 4 fans in series, each could get a maximum of 3V (assuming they are all identica). This is definitely too low voltage and no fan would spin.

If you do however, run them "in series" you could get away with a bigger current Power Supply.

I guess you wanted to say: bigger output voltage, since current consumed by load is reduced.
Refer to Ohm's law.

Btw, the current, marked on fan's case is maximum that could be consumed. Real current could be lower but not necessarily.

If you had a converter that could increase or decrease the voltage, would that have a corresponding effect on the speed of the fan?

Yes, that's how DC-fan's speed could be adjusted.

Btw, i guess that the fan controller in question is nothing more sophisticated than a thermoresistor and some transistors. So there will probably be nothing to hack. I may be wrong of course.