Very basic question from a newb

[Adverse]

Sorry for asking this super-simple question, but i'm looking to hook up this computer fan to an AC adapter :http://www.aocusa.com/pview.php?g=PC%20Cooling&c=FANS%20(DC,%20AC,%205V)&sc=50/52%20mm%20DC&model=FAN-5510-S-3T-L

It has 3 wires, however. red, yellow and black. It is a 12V fan.

What wires should i use? is one of these wires a ground?

Thanks in advance

[audioguru]

Hi Adverse,
Welcome to our forum.
According to the info you provided and Evercool's datasheet http://www.evercool.com/kor/product_list.htm# the fan is designed for 5V. I don't know how much smoke it would make if you applied 12V or more. Usually a 12V AC adapter produces 16V or more when not fully loaded.
Usually, red is positive, black is negative and yellow is ground. Measure ohms with a multimeter to confirm.

[Adverse]

Thanks for the quick response!

However, upon closer inspection, the fan i have in my possession says 12v, it is a similar model to the one in the picture though.

Where would attach the ground wire once confirmed?

Also, when i use my mmeter, what will the ohms tell me?

If i get a reading from the red and black, then they're pos and neg?

If i get no reading then i've got one of the ground wires?

[Adverse]

Thanks for the welcome btw! ;D

[Adverse]

Also, should i test the voltage of the adapter when plugged into the wall? From reading a few posts, its apparent that the Voltage is rarely what is written on the adapter. I don't want to burn the fan out.

Would it be possible to add a variable resistor to control the rpm of the fan? The model number of the fan turns out to be EC5010, i checked that datasheet link out but nothing happened.

If i can add a var resistor, should it be within any specifications? For ex: Voltage, amperes, etc?

[audioguru]

Hi Adverse,
What are you going to use the fan for? If it is not near a radio, TV or not inside a computer, its ground wire doesn't have to be connected.

It is good that its voltage requirement is marked. Just connect it to 12V, with the red wire as positive and the black to negative. If it runs backwards, reverse the wires.

It will probably draw 100mA at 12V, although its manufacturer doesn't say, that's what other manufacturers say for their similar size fans. It would be good to power it from a regulated adapter whose voltage doesn't change. If you use a cheap adapter, its voltage changes with loading. Use a 10V DC cheap adapter rated at 400mA or 500mA. With the 100mA fan its voltage will be about 12V.

To control the speed a variable resistor will be large, expensive, get hot and probably burn out soon. You probably don't need such fine control of the speed, just low, medium and maximum is probably OK. Then you just need a 4-position switch and 2 resistors. The switch would connect one 100 ohm/1W resistor in series with the fan for medium speed and two resistors for low speed. No connection is OFF and direct connection is max.
If a 4-position switch is too expensive, use two cheap on-off switches and one resistor. One switch is for on and off and the other switch controls low or max speed.

[Adverse]

I'm going to be using the fans to ventilate a small greenhouse. There will be a fair amount of water near the work area due to the high humidity in the greenhouse, so i'm guessing i should ground the suckers, right?

The adapter i am using is a Nokia cell phone adapter for charging the battery. Here is what it says on the wart:

ACP-12U

Input: AC 100-240V/ 50-60Hz/180 mA

Output: DC 5.7V/800mA, For ITE use only.

The fans i plan to use are 2 EC5010 12V DC/0.09A/1.2W

When i used my meter on the adapter it read 23.7V. I'm guessing that this has to do with a regulator in the cell phone, bringing it down to 5.7V?

I tried to wire these 2 fans in series, hoping that the combined voltage of 24V would work with this adapter (i have no idea if this is the way it really works, please correct my logic), but only one of the fans would run.

I tried them paralell next and both fans ran fine. WHen i checked the voltage using my meter this time it read 23.7V.

I am now wondering: Is this going to start a fire? Will this burn out the fans or the adapter? Is it a hazard of any other type?

Also, how much does a 4 way swich cost usually?


Thanks again for all the help!!!

[audioguru]

Hi Adverse,
I wouldn't use that adapter. It is not just an ordinary one:
1) Its input voltage range is very wide, from only 100V to 240V. An ordinary adapter is rated at only one input voltage.
2) Its output is rated at 4.56W. But its input is rated at 18W to 43.2W. 38.64W makes a lot of heat for it to get rid of at full load.
3) Its voltage you measured is much too high and I don't know why both fans didn't run in series. In parallel getting nearly double their rated voltage they might overheat or wear out soon.
4) Maybe ITE means intermittant use only.

Buy a 10V DC cheap adapter rated at 500mA. With the 180mA load its voltage will be about 12V. I don't know how many Ruples it would cost (you are in NNE?) but it will cost me 5 bucks.

A Chinese 4 position switch costs me about 3 bucks.

[Adverse]

I'm in Atlantic Canada, so maybe i'll pick up a switch somewhere.

So you say an ideal adapter would be a 10V 0.05A? Wouls this be available at Radio Shack? I'd prefer to buy independant, but maybe RS will have to do.

What do you think about the ground situation?

[audioguru]

Hi Adverse,
I'm a Canuck too, eh! Sorry, I think of NNE as being in the Ukraine.

Don't get a 0.05A transformer, 500mA is what is needed and it's 0.5A. Radio Shack doesn't have a 10V but has a 12V DC/500mA regulated adapter that gives exactly 12V with both your fans connected to it in parallel. It is 20 bucks!
I buy stuff locally at a store with many Canadian branches www.active123.com but they are not in your neck of the woods.

The transformer and fan provide isolation, so grounding (to what?) the fan won't make any difference.

[Adverse]

Hey again,

I found something i think will work for these fans.

I have a Troller Transistorized "Autopulse Transpak 2.5". It is a transformer for a model train set.

It has an output on the back that says "Variable DC 0-12V Track 1". However, when i use my meter to test the actual voltage, it reads as high as ~55V. It uses a knob to change the Voltage. I can set it at 12V exactly, but the fan seems a bit weak at this voltage.

WHy does it say 0-12 when it can go way higher? THe fan is 0.09A, but the transformer doesn't say anything about current... I don't want to burn the fan out or start a fire... How high can i set the voltage without increasing risk of fire or significantly reducing the life of the fan?

Why does the fan seem so weak? At 12V it actually needs a push start to start spinning.

Thanks again

[audioguru]

Hi Adverse,
A model train transformer usually doesn't have a filter capacitor that ordinary adapters have.
Everything that you measure with your meter measures too high. Maybe your meter is broken and you cannot depend on it.
Since you can't measure its output voltage properly, don't use the adjustable train transformer.

[Adverse]

How would i test my meter?? Should i just try to measure the voltage coming from my wall outlet?

[audioguru]

A brand new 9V alkaline battery should measure 9.6V and the meter will be on the same range as 12V for the fans.

[Adverse]

If i could obtain a reliable meter or it turns out that mine is OK, could i use the train transformer?

[audioguru]

I wouldn't use it.
Its description mentions pulses, probably to vibrate the train's motor to start it turning at slow speed. It probably doesn't have a filter after rectification so its DC is also AC. Its rheostat for speed control might get bumped and make the fans burn-out, or the rheostat itself might burn because those thingies aren't designed for continuous use.

[trigger]

I think your meter got some problem....

My 12V DC fan (used inside a PC) will run pretty fast and dangerous (I cut my finger once with it......... :P ) with its input voltage at around 12V.

[audioguru]

Hey, aren't we talking about cheap Chinese fans with only sleeve bearings (no ball-bearings)?
How long do they last with continuous running at full speed? 1 week, 1 month?

[Codyhtml]

hey if if you have an old computer power supply it might save you a lot of hassel if it is an atx look on the internet to figure out how to start it if it is really old then you might not have to any way you could just plug them in but if you have already cut of the adaper or it is a mother board conecter then you still have a great trans former lots of out put and a 5v and a 12v output :)

[Codyhtml]

if it is a dell then it probaly more hassel then it is worth don't use it but also be careful wth them they ground throgh there case so if you touch it when something it making it ground then it can give you a nasty shock (it has happened to me :P) also if it had 3 wires it was probably a motherboard plug but the comp psu would still give good voltage and plenty of current and you could run 5v things too if you wanted to

[Adverse]

OK, here's the deal now:

I have the fan hooked up to a 13.8V Regulated power source with a multi-resistor switch in the circuit. The thing is, on the lowest setting the fan still runs too fast.

In addition to this, the fan stops intermittently only to restart when i touch the power source or switch...

Would lowering the voltage of the power source (getting a diff one) be a better way to regulate the rpm of the fan?

Thanks a lot!!

[audioguru]

Hi Adverse,
The problem with using a resistor to reduce the voltage to the fan is that the voltage changes backwards to what it needs. It the fan slows down for some reason, it draws more current which causes more of the supply's voltage to be across the resistor, not the fan. Hence, even lower speed. You need a constant voltage with the ability to change it.

Why not make an LM317 variable voltage power supply? It will need a minimum of 14VDC input for a maximum of 12V output. Powering both fans with an 8V output, it will just get warm without a heatsink.  http://www.electronics-lab.com/projects/power/010/index.html

What does your defective meter read with the regulated 13.8V supply?

[Adverse]

i used my dad's meter and with the load it read 13.6 i think.

BTW i'm only running one fan now.

[Guest Alun]

PWM is the best way to control the speed of a motor but I wouldn't bother for a fan as it's such low power and the torque isn't critical. A comparator or pair of transistors set up with a potential divider with a thermistor can turn a fan on/off with varying temperature of you could use this simple circuit that operates the transistors in the linear region to make the fan spin faster with increasing temperature.

I would normally warn people against circuits like this but it ok to control the speed of a 150mA fan motor like this. The only really big issue with this circuit is consistency because different fans and transistors will behave differently  so you might have to experiment with different resistor values but as you're only building one it shouldn't be a problem.