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Controlling Cooling Fan Speeds


PotysGSXR

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Hey everyone. I'm setting up my first tank that's NOT using a chiller and I have to say I'm pretty impressed with what a simple cooling fan can do. It's actually bringing my temperature down about 15 degrees (it's a small tank). That said, I feel like it's working a bit TOO well and my heater can't keep up. The temp goes down to 75.5 with the lights off and about 77 with the lights on.

 

Anyone know if I can just buy a 9v dc adapter and just plug it in to reduce the fan speed and noise?

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I s'pose that might wok, but I'm not completely sure... I know that less voltage will usually yield less speed and less cooling...

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filefish949
I s'pose that might wok, but I'm not completely sure... I know that less voltage will usually yield less speed and less cooling...

 

and the more current to get the same power (wattage) the fans will probably fail earlyer on low volatage

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You can safely drop the voltage without harming the fan. I would suggest finding a variable voltage adapter mainly because certain fans will not start below a certain voltage, and that voltage can be different from brand to brand. I'm pretty sure that 7v will start almost any fan.

 

Take a look here too. This could be a very cheap way to garantee that you hit the temp you want with minimal noise. Just modify a few things, like covering the temp sensor with silicone or epoxy, and you're all set. Think of it as an Icecap fan, but $30 cheaper.

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trinichild

I've done the variable trick, get one that has a voltage switch in 1.5 volt increments and drop it down 1.5volt till you get the fan speed you want. I've brought them down to 7.5 volts with a 12 volt fan with good success (depends on the fan). Anything lower and you don't get much cooling.

 

You could go smaller on the fan as well, not sure what size you're using right now. Have you considered running the fan only when the lights are on?

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I have spliced in a larger transformer on a fan, went from 7V to 9V, I needed it to spin faster for better cooling. I would imagine you could do the same and step down a fan.

 

But a variable controller would be the best option since you never know when you want it to cool your tank more some day.

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Transformers would only work for an AC fan (or PWM DC). If you put a transformer on a DC fan it would not work.

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and the more current to get the same power (wattage) the fans will probably fail earlyer on low volatage

 

You sure about this?

 

The motor is a resistor, lets consider it constant (although resistance will change when warm, etc. etc.).

The voltage, once set, is also constant.

Volts / Resistance = Amps.

Volts x Volts / Resistance = Watts

 

How would lowering the voltage increase the amperage?

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omg. my brain is about to explode with all the information. haha. Thank you all.

 

My fan is an AZOO Fan (2)

http://www.azoo.com.tw/azoo_en/modules.php...int&sid=168

 

It works great but is a little loud for the office and the fans are quige large (I think 3 inches each). I would like to get a variable voltage but I'm not sure what that's called in Korean. I think what I'm going to do is try out the 7v adapter for now and see if that won't work.

 

Thanks all!

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shoggoth43
Hey everyone. I'm setting up my first tank that's NOT using a chiller and I have to say I'm pretty impressed with what a simple cooling fan can do. It's actually bringing my temperature down about 15 degrees (it's a small tank). That said, I feel like it's working a bit TOO well and my heater can't keep up. The temp goes down to 75.5 with the lights off and about 77 with the lights on.

 

Anyone know if I can just buy a 9v dc adapter and just plug it in to reduce the fan speed and noise?

 

If it runs on DC you will be fine dropping the voltage. The only thing you'll need to watch for is that the fan starts reliably. Most fans will do this at 7 volts and some will start even at 5 volts. Many will run on less volts but won't start on their own. This wouldn't be a good thing. If you want to manually adjust with a fine amount of control you can just get something like a Zalman Fanmate. http://www.newegg.com/Product/Product.aspx...N82E16835118217 They're pretty cheap and work well.

 

I've also run 12 Volt fans on one of those radio shack multivoltage wall warts. No problems. NOTE: this won't work for the PWM type fans, but you are not likely to run into these in the typically lighting hoods. At least not yet. These are typically 4 wire fans though so you're probably ok as long as you only have 2 or 3 wires.

 

-

S

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7V will definately work w/o any consequences. Any voltage from 0 to 12V will work just don't go over the rated 12V.

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The Propagator

If you use a computer fan ( muffin fan) and a variable amperage selectable adapter you can slow it down by selecting a lower amperage with no problems what so ever. ( might be mille volts or what ever but you know what I mean I'm sure)

You cant use a temp sensor to ramp up the voltage and speed though. You can only do it manually this way.

I am doing this right now on every one of my tanks actually.

 

EDIT: =Don't buy a one setting unit like your looking at. If you can buy a multi setting adapter.

Order it and then buy the Euro adapter or what ever if you have to but its much better IME using th emulti selectable adapter because you can adjust the fans speed manually via selecting a different mille volt setting.

.

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You cant use a temp sensor to ramp up the voltage and speed though. You can only do it manually this way.

I am doing this right now on every one of my tanks actually.

 

Please explain why you think you can't use a temp sensor to change the fan speed. The circuit I linked to is essentially a temperature adjusted voltage regulator and is no different than using a multi-voltage power adapter. The only difference being that it adjusts for you instead of doing it manually all the time. There are other options that do the same thing. There are numerous temperature controlled fans available in the PC industry that do exactly the same thing. Another option is one that has selectable speeds built right in if you want to adjust it manually.

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I think Propagator was talking about PC fans with built in temperature sensors for speed control. I agree that you shouldn't use those sensors because their operating range (~20C to 60C roughly) overshoots an aquarium's optimal temperature. It'd probably work at 30% or something w/o varying the speed much.

 

You can certainly rig up a cct with a comparator or a 555 timer to make an automatic variable speed fan controller. That'd work too.

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The Propagator
Please explain why you think you can't use a temp sensor to change the fan speed. The circuit I linked to is essentially a temperature adjusted voltage regulator and is no different than using a multi-voltage power adapter. The only difference being that it adjusts for you instead of doing it manually all the time. There are other options that do the same thing. There are numerous temperature controlled fans available in the PC industry that do exactly the same thing. Another option is one that has selectable speeds built right in if you want to adjust it manually.

 

Thats exactly what I just said only using an adapter with multiple settings :D

 

and the response above is why I thought and said, you couldnt do it with a PC muffin fan and built in temp sensor. I just couldn't think straight at 5:30 am ;)

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If I could, I would TOTALLY get an adapter that has multiple settings. I'm just not sure where to look. I asked my coworkers and they haven't the slightest idea what I'm talking about. The 7.5v adapter should be coming in today so I'll try it out. Currently, even with my heater on, my fans are bringing my temps down to about 75 and without them on, and with the lights off, my temps are jumping up to about 86 so I need to leave my fans on 24 hours a day. I need to get an ATO quick but they don't sell any here in Korea. I'm having then Tunze Osomolator shipped in from the States.

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well, the problem is, I live in Korea and I reallyd don't want to deal with the shipping expense, transformers, etc.

 

I got the 7.5v and it works well, but just doesnt move enough air so I'm going to be switching it to a 9v tomorrow

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