DIY cooling fans setup cheap :)

**sherchoo** · 16th Feb 2002, 10:49

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On 2/15/2002 1:40:17 AM

A fan is to encourage evaporation lah.. evaporation cause water to lose latent heat of evapoartion...

If you wanna cool you light might as well blow at the light...
You will find that you lose water more when you use a fan..

AC is still not recomended... 240V will kills anything... Dun have to be water splashing on to the fan. The fan can drop into the tank...

And AC fan is powerful... so powerful that your finger will be gone when they meet. :P

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Sorry binbeto,

240Vac does not mean it's more lethal than 24Vdc. The thing that stings/burn us is the current. I've suffered more injuries by DC currents than AC. I got shocked by 480VAC I just got a shocking feeling, abit dazed but no injuries and in when I accidentally touched a 12Vdc leads I got 2 nasty burn mark on my finger. Looked like I got bitten by a bat or something.

Why DC is safer is that in the convertor, there is a tranformer which can isolate any fault on the load side. That's the reason why the CB won't trip the supply as mentioned by Simon.

If you look at your fan (or other electrical device) they usually have the voltage and the current rating. That will give you the capacity of the device.

So don't be fooled by the voltage cos it's the current that kills.

**art** · 16th Feb 2002, 15:27

Alamak , thread for my DIY fan become so luo suo [

]

But yep what sherchoo said is right , its the current that stings , not the voltage. Though more often than not , its almost proportional.

**binbeto** · 16th Feb 2002, 15:46

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Sorry binbeto,

240Vac does not mean it's more lethal than 24Vdc. The thing that stings/burn us is the current. I've suffered more injuries by DC currents than AC. I got shocked by 480VAC I just got a shocking feeling, abit dazed but no injuries and in when I accidentally touched a 12Vdc leads I got 2 nasty burn mark on my finger. Looked like I got bitten by a bat or something.

Why DC is safer is that in the convertor, there is a tranformer which can isolate any fault on the load side. That's the reason why the CB won't trip the supply as mentioned by Simon.

If you look at your fan (or other electrical device) they usually have the voltage and the current rating. That will give you the capacity of the device.

So don't be fooled by the voltage cos it's the current that kills.

I know it's the current that kills.... it the high voltage that cause the current to flow thru...

If voltatge is too low.. the current won't flow thru us...

12V is not strong enuff to cause the current to flow thru our body but 240V is strong enuff to do that..

You can hold the 2 leads of a 12V supply and nothing will happen...

My point is that AC fans is more dangerous than DC fans in an aquarium environment...

**LiquidFX** · 16th Feb 2002, 23:22

Wa. Artvale, nice job sia. I've been wanting to make one too. What type of AC/DC convertor do you use? BTW your floor got a big crack! hahaha...

BTW, if lets say the live wire for the 240AC voltage gets into the the water (without the neutral) and u put your hand inside while you're barefoot. Anyone knows what will happen? Will the circuit breaker trip fast enough not to electrocute you?

**tawauboy** · 17th Feb 2002, 10:36

live wire in water, your hand in tank and you are barefoot = electrocution.
basically you are grounded, that's why.

the circuit breaker would not trip as these are current trip devices.
it is the earth leakage circuit breaker, elcb, that does this job of detecting small amount of electrical leakage.
think the trip levels are around 30mA or so.

and the elcb is supposed to trip under the circumstances described above to prevent electrocution.

me just recalling from some obscure corner of memory as all my electrical stuff was returned to my lecturers the moment i stepped out of school.

**jag** · 18th Feb 2002, 09:40

Quoted from PSB website:

"Earth Leakage Circuit Breaker (ELCB)
- It is a safety device. For households, an ELCB of tripping current 3/100 of an ampere (30mA) and a response time of less than 1/10 of a second (0.1s) is recommended. The ELCB senses any imbalance in the current between the live and neutral wires. It trips when the difference is 30mA or more. This cuts off the electricity supply before the electric shock is lethal "

ELCB does not sense currents in earth wire.

If such an incident does occur, YES the ELCB will trip. YES You'll get a nasty shock! And you would have the ELCB to thank for saving your life.

Generally advised never to use mains electricity near water.

**sherchoo** · 18th Feb 2002, 16:12

Quick theory:

Asumming power remains the same, voltage is indirectly proportional with current.

P=IV

P - Power
I - Current
V - Voltage

Thus, with the reduction of voltage, current increases.

However, I do agree that the DC fan is better/safer for our tanks but bear in mind it's still dangerous.

Juz my 2 cents worth.

**akoh** · 18th Feb 2002, 16:41

Ah! Yah ! buy or build a chiller with ur " Ang Pao " lah ! [

]
Lawrence ! agreed man ! the crack on the floor is plenti bad ! haahaahaaha ! [

]

Akoh
Safe Diving !

**jag** · 19th Feb 2002, 17:52

Sherchoo,

That theory although applied in &gt;450KV power lines not true for low voltage applications.

Power is not assumed to remain constant. In AC-DC converters, they are mainly constant voltage sources. Current will then be a function of load impedance. V=IR =&gt; I=V/R.

Then power can be derived via: P = VI.

Sori to correct you.... just one of my pet peeves....

**CoryDorus** · 1st Jun 2002, 14:47

I think both factors I &amp; V play a part. There is no 100% sole cause factor.

Nevertheless, 12V DC should be safer becoz 2 Mini-Fans will never draw 12A.

When come to Aquarium, is better to be safe then sorry especially so for Aquarists who are always &quot;meddling&quot; with the tank setup.

**peterkoh** · 4th Jun 2002, 17:40

hi there ... the 2 bars .. i presume they will sit across the tank ?? what is it made of and where did you get them ? thanks.

**peterkoh** · 4th Jun 2002, 17:58

even though i'm from engr ... i'm never comfortable with DIY stuff that taps on AC power supply. i had enuf shocks even from a telephone wire (when someone calls in), a 14inch monitor with plug removed but the damn capacitors discharge thru my body when i accidentally touched it.

electricity aside ... watch for those fingers as well. even a 12v dc fan can cut when it's spinning at high speed.

an ac-dc adaptor is much safer really. just my honest opinion.

**art** · 4th Jun 2002, 20:32

Yeap peter, I have had enuff shocks too playing with appliances over the yrs and have found AC isn't my good fren.

If possible i tend not to use AC in any DIY electrical things i do ( if possible ) and strongly advice others not to as well unless really neccesary.

The 2 bars you mentioned arent actually bars....instead they are IC holders...if you walk around Sim Lim tower you can just ask any shop for them , chances are they will give you a whole bunch free.

**clusterbx** · 6th Jun 2002, 14:47

Did the same thing before using 6 CPU fans secured to 2 L-plates and a PC power supply savaged from old computers. It works perfectly well to bring down the steaming hot tank by almost 3 degrees.

Only disadvantage is the space it take up as i line it along the tank (2.5ft) as compared to a single AC fan i had seen.

Never dare to try AC fans because of the risks and hazards involved as my flat has no living things in it except the fishes during the daytime.

**CoryDorus** · 7th Jun 2002, 18:52

Cluster, thanks for the idea on using Power Supply,
I have quite a number of them after year of system upgrades.

**art** · 7th Jun 2002, 21:46

Yep can always use an old AT power supply to power up those fans, best of all they dont need to be wired and jumpered to the motherboard to start.
However do note that current if leaked from the PSU can kill you. In that aspect , the AT psu is not as safe as the ATX one.